Lv book (1).pdf

Vision Technician Course
L V Prasad Eye Institute 1
Anatomy &
physiology of
the eye
VISION TECHNICIAN COURSE
Module 1

2
L V Prasad Eye Institute
CHAPTER 1
INTRODUCTION TO THE ANATOMY OF THE EYE
H
uman eye is one of the five sense organs.The eye allows us to see and interpret the shapes,
colors, and dimensions of objects in the world by processing the light they reflect or
emit. We use our eyes in almost every activity we perform, whether reading or writing,
working on a computer, watching television, or driving a bike.
There are 3 advantages of having two eyes:
Vision with both eyes gives stereopsis (depth perception), which is use for fine tasks like
inserting a key to open a door lock etc.
Vision with both eyes give wider field of view or side vision
If one eye is lost, other eye will act like a spare.
Orbit
The eye is safely enclosed in a bony socket called orbit in the skull.
Eyelids
The eyelids protect the eyes from the environment, and light.They also maintain a smooth corneal
surface by spreading tears evenly over the eye during blinking.The lids are composed of an outer layer
of skin, a middle layer of muscle and an inner layer of conjunctiva.The muscle that helps in closing of
eyelids is called Orbicularis oculi and the muscle that helps in elevation of upper eye is called levator
muscle. Rows of lashes protect the eyes from the dust and debris.

4
Conjunctiva
The conjunctiva is the thin,transparent tissue that covers the outer surface of the eye.It begins at the
outer edge of the cornea, covering the visible part of the sclera, and lining the inside of the eyelids.
The conjunctiva secretes mucous that moisten and lubricate the eye.
Cornea
The cornea is the transparent, avascular, dome-shaped structure covering the front portion of the
eye.It is a powerful refracting surface,providing 2/3 of the eye’s focusing power.The cornea is extremely
sensitive tissue. It comprises of 5 layers: Epithelium, Bowman’s membrane, Stroma, Descemet’s
membrane and Endothelium.Small blood vessels at the outer edge of the cornea,aqueous humor and
tear film provide nourishment to the cornea.
Tear Film
The tear film is comprised of three layers: lipid, aqueous and mucin.The tear film keeps the eye moist,
creates a smooth surface for light to pass through the cornea, nourishes the cornea and provides
protection from injury and infection.
Sclera
The sclera is the tough, opaque tissue that gives protection to the internal parts of the eye. Six
extraocular muscles that control the eye movements and the optic nerve are attached to the sclera.
Limbus
The junction between cornea and sclera is called limbus.
Angle Structures
The area in the anterior chamber where the cornea and iris join is known as the angle. It is made up
of several structures and helps in the drainage of aqueous humor.The aqueous humor is water, like
liquid that fills the space between the cornea and the iris (anterior chamber).It is formed in the ciliary
body, flows through the pupillary space into the anterior chamber and exits out of the eye through
the angle structure.Aqueous humor gives nourishment to the cornea and the crystalline lens.Presence
of aqueous humor in the anterior chamber gives shape to the front portion of the eye.The production
and drainage of aqueous fluid determines the eye’s intra ocular pressure (IOP).
Iris Pupil
The colored part of the eye is called the iris. It divides the eye into anterior chamber and posterior
chamber. Iris is dark brown in color in most of the Indians. Its color comes from microscopic pigment
cells called melanin.The color,texture,and patterns of each person’s iris are as unique as a fingerprint.
The round opening in the center of the iris is called the pupil. It controls light entering the eye.The
sphincter muscle,located at the edge of the pupil and dilator muscle runs radially through the iris, like
spokes on a wheel. In bright light, the sphincter muscle helps in constriction of the pupil and in dim
light, dilator muscle helps in dilatation of the pupil.
Crystalline Lens
The crystalline lens is located just behind the iris. Its main function is to focus light onto the retina.
The lens is suspended behind the pupil with the help of zonules. In young people, the lens changes
its shape and power to adjust for near and distance vision.This is called accommodation.

Vitreous
The vitreous is a transparent gel that fills the eye behind the lens. It is composed mainly of water and
comprises about 2/3 of the eye’s volume, giving it form and shape.
Retina
The retina is a multi-layered photosensitive layer. Its main function is vision. Retina contains millions
of photoreceptors that capture light rays and convert them into electrical impulses.These impulses
travel along the optic nerve to the brain where they are turned into images.
There are two types of photoreceptors in the retina: Cones and rods. Cones are present in the
central area of the retina and help in day vision and colour vision. Rods are spread throughout the
peripheral retina and help in peripheral and night vision.
Centre of the retina is called as macula. It is a small and highly sensitive part of the retina responsible
for clear central vision. The centre of macula is called fovea. The macula allows us to see minute
details and perform tasks that require central vision like reading etc.
Optic Nerve
The optic nerve transmits electrical impulses from the retina to the brain.When examining the retina
through the pupil, a portion of the optic nerve can be seen. It is know as optic disc.
Extra ocular Muscles
The six muscles that surround the eye and control its movements are known as the extra ocular
muscles (EOM).There are 4 rectus and 2 oblique muscles in the eye.All six muscles work as a team
for the smooth movement of the eyes.
Process of vision
Light waves from an object enter the eye through the cornea and pass through anterior chamber and
then through the pupil. Next, the light passes through the crystalline lens.The light waves are bent or
converged first by the cornea, and then further by the crystalline lens.The light continues through
the vitreous humor and forms a clear focus on the retina. In retina, light rays are changed into
electrical signals and then sent through the optic nerve to the brain. The electrical signals are interpreted
by the brain as a visual image.
○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○

6
CHAPTER 2
ANATOMY OF EYELID
The eyelids protect the eyes from the environment, injury and light.They also maintain a smooth
corneal surface by spreading tears evenly over the eye during blinking. Eyebrows are useful for
facial expressions.
The edge of the eyelid is called the eyelid margin.The eyelashes are located on the anterior edge
of the lid margin. Openings of meibomian gland are present on the posterior margin of the eyelid.
The palpebral fissure is the space between the upper and lower eyelid margins when the eyelids
are open.The place where the upper and lower eyelids meet together is called canthus.The medial
canthus is that point nearest to the nose.The lateral canthus is on the other side closest to the
temple.The openings to the tear drainage system are called the lacrimal puncta and are located on
the eyelid margin near the medial canthus. The upper eyelid crease is a horizontal line that is
present on the upper eyelid.
Skin and subcutaneous tissue
The skin of the eyelids is the thinnest of the body. It has hair follicles glands of Moll and Zeis.
Orbicularis oculi muscle
Orbicularis Oculi muscle helps in blinking and closure of the eye. It is supplied by facial nerve (7 th
nerve).
Tarsal plates
The tarsal plates are madeup of thick fibrous tissue and help in maintaining the shape of the lids.Tarsal
plate encloses meibomian glands. Meibomian ducts open at the lid margin.
Orbital septum
The thin fibrous sheet extending from the orbital margin to the tarsal plate is called orbital septum.
It holds back the fat that fills the orbit and cushions the eyeball.
Levator muscle
The muscle that opens the eyelids is called the levator muscle.The small strands of tissue extending
from the levator muscle to the skin form the upper eyelid crease The muscle that helps in the
movement of the eyebrows is called the frontalis muscle.
Muller muscle is supplied by the sympathetic nervous system. It regulates the resting position of
the eyelid.
Posterior part of the lid is lined by palpebral conjunctiva.

Glands of the Eyelid
Meibomian glands – They are enclosed in the tarsal plate.They open on the eyelid margin.
They produce lipid layer of tear film.
Zeis glands – They are present at the base of the eyelashes.
Glands of Moll – They open in the hair follicles or directly into the lid margin.
Nerve supply
Orbicularis oculi muscle – Facial nerve (7 th nerve)
Levator muscle - Oculomotor nerve (3 rd nerve)
Muller muscle - Sympathetic nervous system
SUMMARY OF STRUCTURE FUNCTIONS OF EYELID
Structure Function
Skin It thinnest in the body
Orbicularis Muscle Eyelid closing muscle
Tarsus (Tarsal Plate) It gives shape to the eyelid
Orbital Septum Layer holding back the orbital fat
Levator muscle Opening of the eyelids
Frontalis muscle Forehead muscle that pulls up the eye brows
Orbicularis Muscle Eyelid closing muscle
Conjunctiva Lining of the back of eyelid and front of eye
○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○

8
Cross Section Of Upper Eyelid

CHAPTER 3
LACRIMAL SYSTEM
The lacrimal system consists of two small openings called the puncta,one on upper and the other
on the lower eyelid. Each puncta lead into a small tube called a canaliculus, which, in turn, leads
into the lacrimal sac near the medial canthus.An opening into the lacrimal sac leads into a canal
called the nasolacrimal duct, which passes through the bony structures surrounding your nose and
empties tears into your nasal cavity.
1. Puncta : Punctum are located at upper and lower medial portions of eyelids.
2. Canaliculus : Each puncta are joined by a 2 mm vertical and 8 mm horizontal
canaliculi in the upper and lower aspect. Both canaliculi join to
form common canaliculus.
3. Lacrimal sac : It is 12 mm long, acts as temporary storage area for tears during
blinking.
4. Nasolacrimal duct : It is 15-20 mm long; starts at nasolacrimal sac and ends at inferior
turbinate meatus in nose.
5. Valve of Hasner : It is located at the point where the nasolacrimal duct opens into
the nose. It prevents backward flow of tears from the nose into
the eye.
○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○

10
CHAPTER 4
ANATOMY AND PHYSIOLOGY OF CORNEA
Dimensions:
Vertical Diameter : 10.0 mm - 10.5 mm
Horizontal Diameter : 11.0 mm - 11.5 mm
Thickness in the centre : 0.55 mm (500 microns)
Thickness in periphery : 1.0 mm
Refractive Index : 1.38
Anterior radius of curvature : 7.8mm
Power of anterior surface - +48.0 Ds
Power of posterior - - 5.0 Ds
Cornea is a transparent, dome shaped structure. It does not contain blood vessels like other parts of
the body. The cornea receives its nourishment from the tear film, limbal vasculature and aqueous
humor.
The cornea has 5 layers:Epithelium,Bowman’s Layer,Stroma,Descement’s membrane and Endothelium.
Epithelium
Bowmans layer
Stroma
Descement membrane
Endothelium

Epithelium
The epithelium is the cornea’s outermost region,comprising about 10 percent of the corneal thickness.
It is five to seven cell layers thick and consists of three types of cells; Superficial cells,Wing cells and
Basal cells. Epithelium provides a smooth surface that absorbs oxygen from tears and distributes
these nutrients to the rest of the cornea.The epithelium has the nerve endings supplied byTrigeminal
nerve. It also has micro projections on the outer surface called microvilli, which helps in attachment
of tear film to the cornea.
Bowman’s Layer
Bowman’s layer is a transparent sheet of tissue composed of strong-layered fibers called collagen. If
injured, Bowman’s layer can form a scar as it heals. It does not regenerate.
Stroma
Stroma comprises about 90 percent of the cornea’s thickness. It consists of water and collagen and
does not contain blood vessels. Stroma contains collagen fibrils, keratocytes and ground material
(mucoprotein glucoprotein). The collagen gives the cornea its strength, elasticity, and form. The
collagen’s unique shape,arrangement,and spacing are essential in producing the cornea’s light-conducting
transparency.
Descemet’s Membrane
Descemet’s membrane is a thin and strong sheet of tissue that serves as a protective barrier against
infection and injuries. Descemet’s membrane can regenerate, if injured.
Endothelium
The endothelium is comprised of a single layer of hexagonal shaped cells.Endothelial cells are essential
in keeping the cornea clear. Normally, aqueous humor leaks slowly into the corneal stroma. The
endothelium pumps this aqueous humor out of the stroma.Without this pumping action, the stroma
would swell with water, become hazy, and result in decrease in vision. Once endothelial cells are
destroyed by disease or trauma,they are not regenerated.If too many endothelial cells are destroyed,
corneal edema and blindness may occur.Through the normal aging process, endothelial cell numbers
decrease while cell size increases.A change in the size of cells is referred to as polymegathism, while
the change in the shape of cells is called pleomorphism.

12
Function of the cornea
Cornea acts as the most powerful refracting surface, contributing to 65-75 percent of the eye’s total
focusing power.The cornea also protects the lens and retina from ultraviolet (UV) rays in sunlight.
Tear Film
The tear film comprises of three layers: the lipid layer, the aqueous layer and the mucin layer.
Name of the layer Produced by Function
Lipid layer Meibomian glands Prevent evaporation of
glands of Zeis the tear film
Aqueous layer Lacrimal glands glands Provides nourishment to
of Wolfring and Krause. the cornea and protects
from infection
Mucin layer Goblet cells in the conjunctiva Changes the hydrophobic
corneal epithelium with a
hydrophilic layer
○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○

CHAPTER 5
ANATOMY OF UVEA
Iris, Ciliary body and Choriod together are called Uvea.
Iris
The colored part of the eye is called the iris. It controls light entering the eye.The iris is flat and
divides the eye into anterior chamber and posterior chamber. Its color comes from pigment cells
called melanin.
Mydriasis (dilation) occurs in dimly illuminated conditions, in the state of excitement or fear due to the
action of dilator pupillae muscle.
Miosis (constriction) occurs in brightly illuminated conditions,during convergence and while in sleep and is due
to the action of sphincter pupillae.
Iris consists of three layers.
1. Endothelium: It is made up of modified stroma consisting of a dense collection of fibroblasts,
melanocytes. This layer is deficient in few areas,therefore,the iris stroma is in free communication
with the aqueous humour in the anterior chamber.Large deficiencies in the anterior surface are
called crypts.
2. Stroma: It consists of loose connective tissue containing fibroblasts, melanocytes and collagen
fibres.The loose nature of this tissue and its free communication via openings in the anterior
border layer allows fluid to move in and out of the stroma quickly during dilation and contraction.
It contains following muscles:
(i) Sphincter pupillae: It is 1 mm, narrow circular band surrounding the pupil. It is supplied by
the parasympathetic nerves via 3rd
cranial nerve and causes constriction of the pupil
in bright light.
(ii) Dilator pupillae: These are radial fibres extending from ciliary body to the pupillary margin.
It is supplied by sympathetic nerves and causes dilatation of the pupil in dark.
3. Pigment epithelium: Two layers of pigment epithelium are situated on the posterior surface
of iris. The epithelial cells extend for a short distance onto the anterior iris surface at the
pupillary margin; this is called frill. It can be seen on the pupil margin on slit-lamp examination
of the eye.
Anatomy of ciliary body:
The ciliary body starts at ora seratta, where retina and choroid end. It appears like a triangle with
base forwards. Iris is attached to the middle of the base of the ciliary body.The outer side of the
triangle lies against the sclera with the suprachoroidal space in between.
Ciliary body has two parts:
(i) Pars plicata – The anterior 1/3 of ciliary body (about 2 mm) is known as pars plicata.
(ii) Pars plana - The posterior 2/3 of ciliary body (about 4 mm) is known as pars plana.

14
The ciliary body consists of four layers namely,
Ciliary muscle: These muscle fibres are helpful in accommodation of the lens. On contraction of
ciliary muscle, the zonules of the lens loosen, thereby decreasing the tension on the capsule of the
lens.Then lens power increases for near. Ciliary muscle is innervated by parasympathetic nerves.
Stroma: It consists of loose connective tissue of collagen and fibroblasts, nerves, pigments and
blood vessels.
Ciliary processes: Suspensory zonules are attached to the ciliary processes and the equator of
the lens.Two layers of epithelial cells line each process.The core of the ciliary process contains blood
vessels and loose connective tissue.These processes are the main sites of aqueous production.
Epithelium: There are two layers of pigmented and non-pigmented epithelial cells.
Functions:
(i) Pars plicata secretes aqueous humour.
(ii) The ciliary muscle helps in accommodation of the lens for seeing near objects.
Anatomy of choroid
Choriod is the posterior most part of the Uveal tract. It is a thin and spongy layer. It is spread out
from Ora sereta to the optic nerve.The main function of choroids is the blood supply to rods and
cones.
Choroid is divided into 3 layers; Supra-choroidal Lamina, Stroma and Bruch’s menbrane. Bruch’s
membrane is strongly adherent to the RPE layer of retina.There is a space between sclera and
choriod called suprachoriodal space.
○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○

CHAPTER 6
CRYSTALINE LENS
The crystalline lens of the eye is a transparent, biconvex structure situated between iris and the
vitreous. It is suspended from the ciliary processes and posterior portion of the ciliary body by
means of the suspensory ligaments called zonular fibres.The lens is supported by the vitreous (hyaloid)
face posteriorly.Any insult to the lens can cause a cataract.
The centre of the anterior surface of the lens, known as its anterior pole. Its peripheral margin is
called the equator. Lens has no innervation or blood supply. Its nourishment is obtained from the
surrounding aqueous and vitreous.The lens contains a higher percentage of protein than any other
organ in the body. It contains amino acids and water. News fibres are added through the life and size
and weight of the lens keeps on increasing with age.As new lens fibres are produced, the older fibres
are pushed towards the centre and are compressed in a concentric fashion.
Dimensions:
Equatorial Diameter: 9 - 10mm
Thickness in the centre: 4.0 – 4.5 mm
Refractive index: 1.40
Dioptric Power: +18. 0 D (relaxed state)
The lens consists of three components: Lens capsule, epithelium and lens substance.
The lens capsule is a transparent, highly elastic envelope covering the lens. It has lens epithelium on
the anterior surface.There is no epithelium on the posterior surface.
The lens substance consists of the cortex and nucleus.The lens contains an embryonic nucleus, a fetal
nucleus encircling the embryonic nucleus and adult nucleus. Fetal and Embryonic nuclei are very
difficult to distinguish in older patients.The most peripherally located fibers under the lens capsule
form the lens cortex. Lens cortex lies between epithelium and nucleus in anterior and posterior
surface.
○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○

16
CHAPTER 7
ANATOMY OF RETINA
Retina is the inner most layer of the eye.It is a photosensitive layer and converts light into electrical
impulses and sends them to the brain through the optic nerve.The anterior anterior termination
of the retina is called ora serrata. Central part of the retina is called Macula and it helps in fine central
vision. Central part of the macula is called fovea.The cones predominate in this area.The fovea is the
most sensitive part of the retina.
Retina consists of ten layers:
1. Layer of pigment epithelium – It is a single layer of hexagonal cells containing Melanin
pigment.It is mainly responsible for absorption of light after it has passed through the transparent
anterior layers of the retina.
2. Layer of rods and cones – Cones are responsible for color vision and day vision and rods
are responsible for night vision.Cones are concentrated in the central part of the retina.They
are heavily concentrated in the macular area. Rod cells are longer than the cones.They are
present all over the retina except the macular area.
3. External limiting membrane – It lies between rods and cones and outer nuclear layers.
4. Outer nuclear layer – It consists of nuclei of rods and cones.
5. Outer plexiform layer – It consists of the axons of rods and cones nuclei with the
dendrites of the bipolar cells
6. Inner nuclear layer – It consists of axons of bipolar cells, Horizontal cells Amacrine cells.
7. Inner plexiform layer – It consists of synapses of the axons of the bipolar cells with the
dendrites of the ganglion cells.
8. Layer of ganglion cells – It contains single row of Ganglion cells are present in this layer.
9. Nerve fibre layer – It contains the axons of the ganglion cells.
10. Internal limiting membrane – It separates the retina from vitreous.
○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○

CHAPTER 8
EXTRAOCULAR MUSCLES
The six muscles that surround the eye and control its movements are known as the extraocular
muscles (EOMs). The primary function of the four rectus muscles is to control the eye’s movements
from left to right and up and down. The two oblique muscles move the eye rotate the eyes inward
and outward.
Medial rectus (MR) Lateral rectus (LR)
Superior rectus (SR) Inferior rectus (IR)
Superior oblique (SO) Inferior oblique (IO)
Ocular Movements
Ductions - Monocular eye movements are called ductions.
Versions - Simultaneous movements of both eyes in the same direction are called versions.
Vergences - Simultaneous movement of both eyes in opposite directions is called vergences.
Adduction - Movement of the eye towards the nose
Abduction - Movement of the eye away from the nose
Elevation - Movement of the eye upward
Depression - Movement of the eye downward
Extorsion - Movement of the top of the eye away from the nose
Intorsion - Movement of the top of the eye toward the nose
Extraocular muscle actions and cranial nerve innervation
Muscle Action/s Innervation
Medial Rectus Adduction Lower III
Lateral Rectus Abduction VI
Inferior Rectus Depression
Extorsion
Adduction
Superior Rectus Elevation Upper III
Intorsion
Adduction
Superior Oblique Intorsion IV
Depression
Abduction
Inferior Oblique Extorsion Lower III
Elevation
Abduction

18
The following pneumonic can be used to remember the cranial nerve innervations of
the extraocular muscles:
LR6
(SO4
)3
The lateral rectus (LR) is innervated by C.N. 6, the superior oblique (SO) is innervated
by C.N. 4, and the remaining four muscles (MR, SR, IR, and IO) are innervated by C.N. 3
○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○

CHAPTER 9
VISUAL PATHWAY
The optic nerve is a continuation of the axons of the ganglion cells in the retina. It acts like a
cable connecting the eye with the brain and can be considered as a bundle of nerve fibres. The
portion of the optic nerve that is visible on ophthalmoscopy is called optic disc.The optic disc marks
the starting of the optic nerve where messages from retina leave the eye. Optic disc area is also
known as the ‘blind spot’, as it does not contain rods and cones in this area.
After traveling to some distance, optic nerves from both the eyes cross over and form optic chiasm,
located just below and in front of the pituitary gland. At optic chiasm, the optic nerve fibers coming
from the nasal half of each retina cross over to the other side, but the nerve fibers from the
temporal retina do not cross over and go on straight.
After optic chiasm, the nerve fibers become the optic tract. The left optic tract contains impulses of
images from the right visual field and the right optic tract contains impulses from the left visual field.
Each optic tract terminates in the lateral geniculate nucleus (LGN) in the thalamus and fans into the
optic radiation to reach the visual cortex in the occipital lobe at the back of the brain.
The visual cortex interprets the electrical signals produced by light stimulation of the retina into the
images.Thus images can be seen.
○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○

20
Visual Pathway

CHAPTER 10
NERVE SUPPLY TO THE EYE
The upper division of the oculomotor nerve (cranial nerve III) innervates the superior rectus and
the levator palpebrae superioris muscles.The lower division of cranial nerve III innervates the
inferior rectus, medial rectus, and inferior oblique muscles. The trochlear nerve (cranial nerve IV)
innervates the superior oblique muscle.The abducens nerve (cranial nerveVI) innervates the lateral
rectus muscle.
The iris controls the size of the pupil. The sphincter pupillae muscle is a circular muscle, which
constricts the pupil, under the control of parasympathetic fibres, which arise in the brain and travel
with the oculomotor nerve to the orbit. In the orbit the fibres synapse in the ciliary ganglion then
pass into the eye to innervate the muscle.The dilator pupillae muscle is a radial muscle, which dilates
the pupil, controlled by sympathetic nerve fibres.
Dilation and constriction of the pupils occurs in a conjugate fashion. Shining a bright light in one eye
will send impulses through that optic nerve to the CNS. Efferent impulses will travel out through the
oculomotor nerves to both eyes to cause simultaneous constriction of the pupils.
○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○

22
CHAPTER 11
BLOOD SUPPLY TO THE EYE
The major blood supply to the eye comes from the ophthalmic artery.The lateral muscular branch
of the ophthalmic artery supplies the lateral rectus,superior rectus,and superior oblique muscles.
The medial muscular branch supplies the inferior rectus, medial rectus, and inferior oblique muscles.
Medial and lateral muscular branches of the artery give rise to 7 anterior ciliary vessels, which travel
with the 4-rectus muscles to provide circulation for the anterior segment of the eye. Each rectus
muscle has 2 anterior ciliary vessels, except for the lateral rectus muscle (which has 1 vessel).These
vessels pass anteriorly to the episclera and supply the anterior segment of the eye, including the
sclera, limbus, and conjunctiva.
○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○

Ocular diseases
Module 2

24
CHAPTER 1
DISORDERS OF EYE LIDS
Ectropion
Ectropion is outward turning of the lid margin away from the globe.Long standing ectropion may lead
to corneal exposure, watering, keratinization of the palpebral conjunctiva, and defective vision due to
corneal scarring. Ectropion can affect any age but most commonly is seen in older adults. Surgey can
be done to correct ectropion.
Entropion
Entropion is a inward turning of the lid margin. It mostly affects the lower lid. It can be caused due to
various reasons.When the eyelid turns inward, the lashes rub against the eye and cause irritation,
watering and redness. Surgey can be done to correct entropion.
Ptosis
Abnormally low position of the upper lid or drooping of the upper eyelid is called Ptosis.It may occur
due to disease, injury, birth defect, previous eye surgery and age. In most of the cases, it is caused
because due to a weakness of the levator muscle or a problem with the 3rd
cranial nerve.
Children born with ptosis (congenital ptosis) may require surgical correction of the ptosis,if it covers
the pupil to avoid stimulus deprivation amblyopia.In some cases,it may be associated with strabismus.
Surgey can be done to correct Ptosis.
Blepharitis
Blepharitis is a chronic inflammation of lid margins caused by seborrhea or staphylococcal infection.
In Staphylococcal Blepharitis hard and brittle scales are present around the bases of the
eyelashes.
In seborrheoric Blepharitis, the scales are soft and greasy and may be found anywhere on the
lid margin and on the lashes.
Left untreated chronic blepharitis can cause ulcerative blepharitis,meibomitis,hordeola,chalazia
and marginal sterile keratitis.
Signs and symptoms
It is always bilateral. Symptoms vary but may include any or all of the following: itching, burning,
foreign body sensation, watering and crusty debris around the eyelashes, especially upon waking up in
the morning.
On examination,lid erythema,collarettes (crusts around the eyelashes),madarosis (loss of eye lashes),
trichiasis (misdirected eye lashes), conjunctival congestion and superficial punctate keratitis on the
lower third of the cornea can be seen.
Ulcerative Blepharitis: It is an infection caused by staphylococci characterised by deposition of crusts
at the roots of the eyelashes and lid edema.The crusts will leave small round ulcers when removed
associated with mild bleeding.

Treatment
Scrubbing of lid margins daily with cotton bud dipped in a 25% solution of baby shampoo.
(Johnson Johnson).
Antibiotic ointment can applied on the anterior lid margin with a cotton bud or a clean finger
after removing the crusts
Tear substitutes, if patient has dryness irritation
Oral tetracycline for severe cases
Meibomitis
It is a chronic inflammation caused due to obstruction of the meibomian gland secretions. Secretions
can be expressed from the orifices on application of pressure on the tarsus. Oily secretion is can be
seen on the meibomian gland orifices. It is always bilateral. Patient complains of Itching , Burning
foreign body sensation.
Treatment
Warm compress lid scrubs
Tear substitutes, if patient has dryness irritation
Oral tetracycline for 6-12 weeks for severe cases
Internal Hordeolum
It is an acute infection of the meibomian glands caused due to staphylococcal infection. It presents as
a tender, inflamed swelling on the eyelid. It may form an abscess.Treatment comprises of incision and
drainage of the abscess, antibiotics and analgesics.
External Hordeolum (Stye)
It is an acute staphylococcal infection of the Zeis glands. It presents with painful swelling with pus
formation at the lid margin.Hot compress can be given to reduce the symptoms.It may need epilation
of the infected eyelash or excision and drainage of the abscess.Antibiotic ointment can be prescribed.
Chalazion
It is a chronic inflammation of the meibomian glands caused due to the stagnation of the secretions.
It is seen as a round, painless, hard lesion of on the eyelid. It may cause blurred vision due to induced
astigmatism and mechanical ptosis. It may be associated with chronic Meibomitis. In the early stages,
warm compresses lid massage are advised. Surgery done, if it does not decrease or recurs after
sometime. (Incision and curettage).
Lagophthalmos
It is a condition in which the eyes cannot be closed completely. It leads to dryness scarring of the
cornea. Artificial tears and ointment are prescribed and surgery (tarsorrhaphy) is done in severe
cases.
○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○

26
CHAPTER 2
DISEASES OF CONJUNCTIVA
Conjunctivitis
Conjunctivitis is an infection of the conjunctiva.The three most common types of conjunctivitis are:
viral,allergic and bacterial.Except the allergic conjunctivitis,other types of conjunctivitis are contagious
and can spread from one person to another.
The viral conjunctivitis is commonly caused due to adeno virus.Allergic conjunctivitis may be caused
by intolerance to substances such as cosmetics, perfume, or drugs. Bacterial conjunctivitis is caused
by staphylococcus and streptococcus.
Viral conjunctivitis
Signs and Symptoms
Watery discharge
Irritation
Diffuse congestion, chemosis
Lid edema
Infection usually begins with one eye, but may spread easily to the other eye
Diagnosis
Diagnosis is based on the type of discharge and signs symptoms clinically.
Treatment
There is no cure for viral conjunctivitis, usually resolves within 3 weeks
Symptoms can be relieved with cool compresses and artificial tears
Topical steroid drops may be prescribed, in severe cases
Allergic conjunctivitis
Signs and Symptoms
Ropy discharge
Diffuse congestion
Itching
Watering
Lid edema
Diagnosis
The cause of Conjunctivitis can be diagnosed clinically based on signs and symptoms.

Treatment
Cool compresses and artificial tears
Non-steroidal anti-inflammatory medications, steroids and antihistamines, in severe cases
Bacterial conjunctivitis
Signs symptoms
Mucopurulent discharge that may cause the lids to stick together, especially after waking up in
the morning
Diffuse congestion
Watering
Irritation
Usually affects only one eye, but may spread easily to the fellow eye
Diagnosis
The cause of Conjunctivitis can be diagnosed clinically.In some cases,cultures are taken to determine
the type of bacteria causing the infection.
Treatment
Antibiotic eye drops
To avoid spreading of conjunctivitis:
Disinfect surfaces such as doorknobs and counters with diluted bleach solution
Avoid touching the face again and again
Wash hands frequently
Don’t share towels or washcloths
Do not reuse handkerchiefs (using a tissue is best)
Avoid shaking hands
Neonatal Conjunctivitis
Neonatal conjunctivitis occurs during the first month after birth.It is caused by Bacteria,Chlamydia
or virus. Chlamydia is the most common. Infants acquire these infective agents as they pass through
the birth canal during the birth process.
Gonococcal conjunctivitis
Gonococcal conjunctivitis is the most serious condition, usually occurring 24-48 hours following
birth.The child is presented with bilateral acute conjunctivitis, associated with lid edema, chemosis,
and purulent discharge. Corneal ulcer and perforation may occur, if treatment is delayed.
Chlamydial conjunctivitis
It is the most common type of neonatal conjunctivitis,occurring 7-14 days after birth.The presentation
of chlamydial conjunctivitis may range from mild hyperemia with mucous discharge, eyelid swelling,
and chemosis and pseudo-membrane formation. Most cases are mild and self-limited; it occasionally
may lead to corneal involvement and scarring.

28
Treatment
2.5% povidone-iodine solution is useful in preventing neonatal conjunctivitis
Bacterial conjunctivitis is treated using Erythromycin or bacitracin ointment, Gentamycin or
tobramycin eye drops
Chlamydial conjunctivitis is treated using erythromycin ointment
○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○

CHAPTER 3
DIFFUSE CONGESTION VS. CIRCUMCILIARY CONGESTION
Feature Diffuse congestion Circumciliary congestion
Location Near fornix Around cornea
Colour Bright red Pale red
Branching Dichotomos Radial around cornea
Movement Vessels can be moved Vessels cannot be moved
Importance Not serious Serious (internal structures are involved
Example Conjunctivitis Uveitis
○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○

30
CHAPTER 4
RED EYE - DIFFERENTIAL DIAGNOSIS
Red eye is one of the most common presenting condition the eye clinics.It is essential to distinguish
the difference between the serious condition and non-serious conditions.
Clinical feature Possible cause
Discharge Conjunctivitis
Severe eye pain Iritis, keratitis, acute angle-closure glaucoma,
scleritis, orbital cellulitis
Photophobia Iritis, keratitis
Impaired vision (few days duration) Iritis, keratitis, acute angle-closure glaucoma,
orbital cellulitis
Hazy cornea Keratitis, acute angle-closure glaucoma
Corneal infiltrate Keratitis
Circumcorneal congestion Iritis, keratitis
Flare cells in the anterior chamber Iritis
Pain on palpation of the eye Scleritis , orbital cellulites
Proptosis Orbital cellulitis, posterior scleritis,Thyroid
eye disease
Restricted or painful, extraocular eye Orbital cellulites
movements
Fever Orbital cellulitis, viral disease
Severe pain with lid eye with lid edema Endophthalmitis
Nausea and vomiting Acute angle-closure glaucoma
Small, irregular, ill sustained pupil Iritis
Fixed mid-dilated pupil Acute angle-closure glaucoma
Increased intra-ocular pressure Acute angle-closure glaucoma, iritis
History of connective tissue diseases Necrotising scleritis
(joint pains)
○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○

CHAPTER 5
EPISCLERITIS SCLERITIS
Episcleritis is an inflammatory condition affecting the episcleral tissue that lies between the conjunctiva
and the sclera. It is a mild, self-limiting, recurrent disease.
There 2 clinical types are simple and nodular.
Signs and symptoms
Mild pain
Localised or diffuse congestion
Photophobia
A freely moveable nodule may be present in the nodular type of episcleritis.
Treatment
Self-limiting disease
Artificial tears
Topical corticosteroids (prednisolone or betamethasone eye drops, in severe cases (Nodular
type)
Scleritis
Scleritis is a chronic, painful, and potentially blinding inflammatory disease. It commonly is associated
with systemic autoimmune disorders like rheumatoid arthritis. Scleritis may be classified into anterior
and posterior.
Signs and symptoms:
Severe pain
Localised or diffuse congestion
Watering
Photophobia
Decreased visual acuity, in severe cases
Treatment
Non steroidal anti-inflammatory drugs (NSAIDs)
Corticosteroids or immuno-suppressive drugs
○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○

32
CHAPTER 6
INFECTIOUS KERATITIS
Infectious keratitis are a group of conditions caused due to invasion of the corneal epithelium and
stroma by microorganisms. Keratitis can be caused by:
Bacterial, viral, or fungal infections
Allergic reaction
Vitamin A deficiency
Bacterial keratitis
Bacterial keratitis is a sight-threatening disease with severe symptoms. It progresses rapid and causes
corneal perforation within 24-48 hours with some bacteria.The most common groups of bacteria
that cause bacterial keratitis are Streptococcus, Pseudomonas, Staphylococcus etc.
Signs Symptoms
Sudden onset of pain, photophobia, and decreased vision
Lid edema
Circumciliary congestion
Corneal epithelial defect; grayish – white corneal infiltrate;
Stromal edema is present surrounding the lesion
Increased anterior chamber reaction with or without hypopyon
Treatment
Scrapings of the corneal ulcer to identify the microorganism
Antibiotics (Tobramycin, Chloramphenicol, Gentamycin eye drops etc.)
Therapeutic penetrating keratoplasty, medical treatment fails
Fungal keratitis
Fungi enter into the corneal stroma through a defect in the epithelium, then multiply and cause tissue
death and an inflammatory reaction. The epithelial defect mostly results from trauma mainly with
plant material.This is the reason why; it is common in agricultural countries like India.
Signs Symptoms
History of injury in the eye with plant material
Pain
Decrease in vision
Photophobia
Circumcilairy congestion
Epithelial defect

Stromal infiltration, with satellite lesions and brown pigmentation
Anterior chamber reaction
Hypopyon
Treatment
Antifungal agents include natamycin, amphotericin B, ketoconazole, miconazole, fluconazole,
and clotrimazole
Therapeutic penetrating keratoplasty, if medical treatment fails
HSV keratitis
In Herpes Simplex virus (HSV I) the infection of cornea, the corneal lesions that look like the veins of
a leaf are seen.This is known as called dendritic keratitis. Repeated episodes of dendritic keratitis can
cause permanent scarring,and loss of sensation of the cornea.Recurrent dendritic keratitis is followed
by disciform keratitis. It is characterized by central, disc-shaped swelling of the cornea and by
inflammation of the iris.
Herpes Zoster Infection
It is caused by the varicella-zoster virus. It may travel to the head, part of the nose, mouth, cheek, and
forehead and cause blistering rashes, fever and painful inflammation of the affected nerves.The virus
may also infect the cornea.The corneal lesions heal,but may cause scarring of the cornea and decreased
corneal sensitivity.
Treatment
Anti viral agents (Ocuvir,Acyclovir)
○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○

34
CHAPTER 7
GLAUCOMA
Glaucoma is a disease in which intraocular pressure is elevated to cause damage to the visual field.
Classification:
Glaucoma is classified into primary glaucoma and secondary glaucoma. Primary glaucoma is further
classified into Primary Open angle glaucoma and Primary Angle closure glaucoma.
Open angle glaucoma is caused due to the elevation in IOP caused due to increased resistance in
the trabecular meshwork.
Angle closure glaucoma is caused due to obstruction to the aqueous humour out flow due to
mechanical closure of anterior chamber angle by the peripheral iris.
Based on the age of onset of glaucoma, it is divided into congenital, infantile, juvenile and adult
glaucoma.
Methods of examination
Tonometry:
IOP is measured using an instrument called Tonometer. The process is calledTonometry. Tonometer
can be an indentation Tonometer (e.g. Schiotz Tonometer) or Applanation Tonometer. (E.g. Goldman,
Perkins).

Gonioscopy:
Gonioscopy is a process of examining the width of an anterior chamber angle. Anterior chamber
angle is not visible through the cornea due to total internal reflection. Gonioscope eliminates the
total internal reflection and helps to view the angle structures.
Perimetry:
Perimetry is the process of charting / recording the visual field. Visual field is defined as an island of
vision surrounded by sea of darkness. The visual field extends to 60 degrees nasally, 50 degrees
superiorly, 90 degrees temporally and 70 degrees inferiorly.
Static Perimetry:
The stimulus is presented in a predetermined position for a preset duration.
E.g. Humphery visual field analyser.
Kinetic Perimetry:
A stimulus of known luminance is moved from non-seeing area to seeing area and visual field is
plotted.
E.g. Goldman,Tangent Screen, Confrontation.
Parameter Instrument Normal
Intraocular pressure Tonometer (Goldmann
applanation tonometer) 10 - 20 mm Hg
Anterior chamber angle Gonioscope Open angle
Anterior chamber Slit lamp / Oblique flash light test Deep Quiet
Visual field Perimeter ( Humphrey Nasal - 60 degrees
Visual field Analyser), Superior - 50degrees
Confrontation Temporal - 90 degrees
Inferior - 70 degress
PRIMARY OPEN ANGLE GLAUCOMA (POAG):
It is also called Chronic Simple Glaucoma. It is characterised by:
IOP 21 mm of Hg.
Open angle
Glaucomatous disc damage Visual Field damage
Clinical features:
POAG has an insidious onset, and usually patient is asymptomatic until there is a significant visual field
damage.
Initial treatment is medical and the target is to reduce IOP and stop Disc damage. Topical beta-
blockers (Timolol or Betaxolol) are used as first line of management.Filtering surgery (Trabeculectomy)
is done for uncontrolled glaucoma. The aim of the surgery is to create a new canal for aqueous
outflow.

36
PRIMARY ANGLE CLOSURE GLAUCOMA (PACG):
Primary angle closure glaucoma consists of 5 overlapping phases.
Latent
Intermittent (sub acute)
Acute
Chronic
Absolute
Latent phase is asymptomatic and characterized by a shallow anterior chamber, a convex shaped iris-
lens diaphragm, close proximity of the peripheral iris to the cornea and a normal IOP. Gonioscopy
shows a narrow angle capable of closure.
Intermittent (sub acute) stage occurs due to rapid partial closure and reopening of the angle resulting
in temporary elevation of IOP. The attacks may be precipitated by physiological mydriasis (watching
movie in a dark room), or by physiological shallowing of the anterior chamber when the patient
assumes a prone or semi-prone position (as when seeing or reading).
The symptoms of intermittent PACG include transient blurring of vision associated with colored
haloes around lights due to corneal edema. Patient may complain of eye ache or frontal headache.
Attacks are recurrent and normally broken after one or two hours by physiological miosis (exposure
to bright light or sleep).
Acute angle closure glaucoma occurs due to sudden total closure of the angle, which causes severe
elevation of IOP. Patient presents with complaints of severe eye pain, defective vision, and redness.
Some patients may complain of nausea and vomiting. On examination, there will be congestion of
conjunctiva, corneal epithelial edema. Anterior chamber is usually shallow and pupils will be vertically
oval, fixed and mid dilated.
Chronic angle closure glaucoma is also called creeping angle closure glaucoma, because the angle
becomes closed very slowly over a period of time. Patient does not have any symptoms till the late
stage of the disease.
Absolute angle closure glaucoma is an end stage glaucoma, where the eye is completely blind and
treatment is given only to relieve pain by learning IOP.
Primary angle closure glaucoma is treated by peripheral iridectomy or laser iridotomy.Hyper-osmotic
agents are given to reduce IOP in acute angle closure glaucoma. Pilocarpine eye drops are given four
times a day as a medical treatment. Cyclocryotherapy is a process of destroying secretary ciliary
epithelium to reduce IOP.

CONGENITAL GLAUCOMA
Congenital glaucoma is present at birth. It may occur because of a malformation of the anterior
chamber angle. It is called as infantile when it is present within the first year of life. It is mostly a
bilateral condition. It is also associated with high myopia.Congenital glaucoma may be associated with
many systemic conditions.
Signs symptoms:
Enlarged and hazy cornea
Increased IOP
Photophobia
Watering
Blue sclera
Treatment
Trabeculotomy and/or trabeculectomy may be performed to reduce the IOP.
○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○

38
CHAPTER 8
UVEITIS
Inflammation of any part of the uveal tract is called uveitis.The uveal tract of the eye consists of the
iris,ciliary body,and choroid.Uveitis is most commonly classified as anterior,intermediate,posterior,
or diffuse.
Anterior uveitis includes iritis and iridocyclitis. Intermediate uveitis includes the inflammation of
ciliary body and pars plana (cyclitis and pars planitis). Intermediate uvetitis is painless and patient
complaints of floaters.
Symptoms and Signs
Anterior Uveitis is the most symptomatic.
Photophobia
Blurred vision
Pain
Small pupil
Slit-lamp examination shows cells and flare in the aqueous humor and/or keratic precipitates (clumps
of cells and protein material) on the corneal endothelium.
Treatment
Topical Cortico-steriods are given to control inflammation
Cycloplegic agents are prescribed to control the pain and avoid posterior synechia formation.
○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○

CHAPTER 9
CATARACT
Any opacity of the lens or loss of transparency of the lens is called Cataract. Cataract is the most
common cause of blindness in many parts the world. It is most common in developing countries
and mostly affects the patients after 50 years, however, cataract can occur at any age.
Classification
Morphological Classification (location)
Capsular
Subcapsular
Nuclear
Cortical
Stage of Maturity
Immature
Mature
Intumescent
Hypermature
Morgagnian
Signs and Symptoms
Glare: Night vision and driving becomes difficult due to posterior sub capsular cataract
Gradual painless decrease in vision. Near vision is worse in PSC and distance vision is
worse in nuclear cataract.In central PSC the vision is worse in bright light but improves in dim
illumination.
Colored Halos: Patients with early cataract complain of coloured halos around the light
source.
Anterior Chamber: Depth of anterior chamber is shallow in intumescent cataract and deep
in hypermature-partially absorbed cataract.
Iris Shadow: In immature cataract a shadow of the iris is seen in the pupil on oblique
illumination. In mature cataract iris shadow is not visible.
Detection diagnosis
1. Distant Direct Ophthalmoscopy (DDO):Cataract appears as black patch against the red
glow from the fundus when seen with direct ophthalmoscope/ retinoscope from a distance of
50 – 60 cms in a dimly illuminated room.
2. Slit lamp examination: The areas and density of the cataract can be graded by examining
the lens with dilated pupils on a slit lamp.

40
Complications of Cataract
1. Phacomorphic Glaucoma:Lens may swell by absorbing aqueous resulting in shallow anterior
chamber.The angle may close blocking the trabecular meshwork and raised IOP.
2. Phacolytic Glaucoma: In hypermature cataract, the lens proteins leak out into the anterior
chamber and block the trabecular meshwork causing increase in IOP.
Treatment
Cataract extraction surgery is the only treatment option available for cataract. Artificial lens called
intraocular lens is implanted during the surgery. IOLs are made of PMMA (Polymethyl Methacrylate),
Silicone or Acrylic (foldable). Cataract surgery is one of the safest surgery.
Types of cataract surgery
1. Extra-capsular cataract extraction (ECCE)
2. Intra-capsular cataract extraction (ICCE)
3. Pars plana lensectomy
4. Phacoemulsifiation
5. Small incision cataract surgery
Intra-ocular lens (IOL) types:
1. Posterior chamber Intraocular lens (PCIOL)
2. Anterior chamber Intraocular lens (ACIOL)
The power of intraocular lens is calculated using the values of keratometry and axial length of the eye
in a formula (SRK Formula).
After-Cataract (PCO)
Opacification of posterior capsule after ECCE or Phacoemulsification caused due to re-growth of
lens epithelial cells from the anterior capsule is called after-cataract or posterior capsular opacification.
If it leads to significant decrease in vision then an opening is made in the posterior capsule with the
help of Nd-YAG Laser (Neodymium - Yttrium Aluminum Garnet Laser).
ECCE vs. ICCE
ECCE ICCE
Lens removal Nucleus removed Lens removed as single piece
out of the capsule within its capsule
and cortex taken out
Posterior capsule zonules Intact Removed
Incision Smaller Larger
High tech equipment Required Not required
Time taken More Less

IOL Implantation Posterior chamber No IOL or ACIOL
Expertise required Difficult technique Easier
Cost More Less
PCO Possible No PCO / After-Cataract
LENS ABNORMALITIES
Dislocation of Lens: Absence of lens from the pupillary area
Lenticonus - Anterior surface of the lens (rarely posterior surface) is projected into a conical
projection giving rise to high myopia.
Lens Coloboma - A notch shaped defect is found in the equator of the lens.
Spherophakia - Lens surface more curved than the normal. But the size of the lens can be normal.
Patient’s with spherophakia will have high lenticular myopia.
Microspherophakia - Lens surface more curved than the normal. But the size of the lens can be
small.
○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○

42
CHAPTER 10
DISEASES OF RETINA
Retinal Detachment
A retinal detachment occurs when the sensory retina and retinal pigment epithelial layer separate.
Retinal detachment is considered an ocular emergency that requires immediate medical attention
and surgery. It may occur in patients with high myopia, diabetic retinoipathy and severe inflammation
in the back portion of the eye.
Signs and Symptoms
Light flashes
Wavy vision
Veil or curtain obstructing vision
Floaters
Sudden decrease of vision
Detection and Diagnosis
By examining the retina with indirect ophthalmoscope with full pupillary dilation
Ultrasound B-SCAN is useful to get additional details of the detachment
Treatment
Surgery (scleral buckling or silicone oil injection into vitreous)
Systemic steroids for Haradas disease
Retinitis Pigmentosa
Retinitis Pigmentosa (RP) is a rare, bilateral, hereditary disease that causes gradual degeneration
of the rod photoreceptors in the retina. Rods are located in the periphery of the retina and are
responsible for peripheral and night vision. It affects males more than females.
Signs and Symptoms
Difficulty seeing dim lighting
Tendency to bump into objects in poor lighting conditions
Gradual loss of peripheral vision
Glare
Loss of contrast sensitivity

Classic signs of RP
Clumps of pigment in the peripheral retinal called “bone-spicules”
Arteriolar attenuation (thinning retinal arteries)
Waxy disc pallor
Electroretinography (ERG) may be performed to study the retinal response to light stimuli.The
test gives the information about the function of the rods and cones in the retina.
Treatment
There is currently no standard treatment for retinitis pigmentosa
Services of the sight enhancement centre and visual rehabilitation can be very helpful in
improving the quality of life of the diseased individuals.
Macular Degeneration
Age-related macular degeneration (ARMD) is a degenerative condition of the macula. It affects
those who are 50 years or older. ARMD affects central vision only and does not cause total blindness
because it does not affect the peripheral vision.
Classification of ARMD
ARMD is classified as
Wet (neovascular, exudative)
Dry (non-neovascular).
Wet ARMD is more severe and causes drastic reduction in vision within few days. Dry ARMD is
more common and causes gradual decrease in vision.
Signs and Symptoms
Loss of central vision: Gradual - Dry ARMD
Sudden - Wet ARMD
Difficulty reading or performing tasks that require the ability to see detail
Metamorphopsia (Distorted vision -Straight lines appear wavy)
Drusen - earliest clinical finding in of ARMD
RPE changes at macula
Amsler grid test
Fluorescein angiography
Retinal exam is performed using slit lamp and + 78 D or +90 D Lens or direct ophthalmoscope.

44
Treatment
No treatment for dry ARMD
Laser, in some cases of wet macular degeneration
PDT (Photodynamic therapy), in some patients with wet AMD (very expensive treatment)
Low vision devices like magnifiers, reading aids etc for rehabilitation
Diabetic Retinopathy
Diabetes Mellitus
Diabetes mellitus is a metabolic disorder in which there is a failure to utilise glucose and caused
increase in blood sugar levels. If it is uncontrolled for long time, it will damage the retina, brain and
kidney.
Diabetes is of 2 types
Insulin dependent diabetes (IDDM)
Non-insulin dependent diabetics (NIDDM)
Types of Diabetic Retinopathy
Non-proliferative diabetic retinopathy
Proliferative diabetic retinopathy.
Non proliferative is the early stage of the disease and does not affect the vision.Proliferative retinopathy
is more severe and causes decrease in vision due to various complications.
Signs symptoms
Sudden loss of vision due to Vitreous hemorrhages
Fluctuation in vision due to changing refractive errors
Cotton wools spots, hemorrhages, new vessels on retina
Detection diagnosis
Fundus examination using a direct ophthalmoscope or using a slit lamp and either a contact
lens or a 78D lens
Treatment
Control of Diabetes
Laser Photocoagulation
Surgery - Vitrectomy is done for vitreous haemorrhage
○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○

CHAPTER 11
DISEASES OF OPTIC NERVE
All the optic nerve diseases cause RAPD, visual field defect and color vision deficiency. During
clinical examination the patient, if there is an explained visual loss on, colour vision test using
Ishihara chart, pupil assessment using swinging flash light test and visual field testing by confrontation
should be performed.
Optic atrophy
Optic atrophy can be defined as dysfunction of the optic nerve; it may be congenital or acquired. If it
is congenital, it is usually hereditary.Optic atrophy can primary or secondary. Optic atrophy is an end
stage of optic nerve disease. It can occur due to inflammation, toxins, tumours in the brain etc.
Signs and Symptoms
Pale optic disc
Gradual decrease in vision.
Defective Color vision and contrast sensitivity
Treatment
No treatment is available for optic atrophy in majority of the cases. Most patients can benefit
from services of low vision and rehabilitation.
○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○

46
CHAPTER 12
EXTRAOCULAR MUSCLE PALSIES
Oculomotor nerve (cranial nerve III)
The III nerve supplies the levator palpebrae, the pupillary sphincter and all the extraocular muscles
except the lateral rectus and the superior oblique. It is divided into 2 branches.
The superior division innervates
Superior rectus
Levator superioris muscles
The inferior division innervates
Inferior rectus
Medial rectus
Inferior oblique muscles
Pupil via innervation to the iris sphincter muscle
Signs symptoms in III nerve palsy
Eye will be turned outward and downward (due to unopposed action of the lateral rectus and
superior oblique muscles)
The affected eye does not move inward and upward beyond the midline
Ptosis
Mid-dilated and fixed pupil
Trochlear nerve (cranial nerve IV)
The trochlear nerve supplies to the superior oblique muscle.
Signs symptoms in IV nerve palsy
Acute onset of vertical diplopia, worse in down gaze
Head tilt to opposite shoulder
Head turn downward with chin depressed, eyes up.
Face turn to opposite side.
Hypertropia of the affected eye
Abducens nerve (cranial nerveVI)
Abducens nerve innervates the lateral rectus muscle.

Signs symptoms inVI nerve palsy
Esotropia - greater for distance than for near
Face turn toward the side of the palsy
Diplopia
Treatment for all extra ocular muscle palsies
Prisms – Some patients may get relief with prisms in glasses.
Occlusion - A patch or frosted lens may be placed over one eye avoid diplopia.
Surgery - Surgical correction if amount of squint remain stable for at least six months.
○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○

48
CHAPTER 13
DISEASES OF THE ORBIT ADNEXA
Orbital cellulitis
Orbital cellulitis is an acute infection of the tissues surrounding the eye. It is caused due to spreading
of bacterial infection from the sinuses.It is also caused due spread of infection from stye or trauma to
the eyelid.
In children,orbital cellulitis is spread from sinus infection caused by organisms like Hemophilus influenzae,
Staphlococcus aureus and Streptococci.
Signs symptoms
High fever
Painful swelling of upper, lower lids tissues around the eye
Decreased vision (because the lid edema)
Proptosis (forward displacement of the eye)
Restricted or painful eye movements.
Detection and diagnosis
Careful history and external examination is helpful in coming to a diagnosis. In some children, CT
scan or MRI of the sinuses and orbit may be useful.
Treatment
Hospitalization and intensive treatment with IV antibiotics should be started immediately. Surgical
drainage of an abscess may be necessary.The patient can recover completely if it is diagnosed early
and treatment is given promptly. Proper evaluation and early treatment of sinus, dental, or other
infections may prevent the spread of infection to the eye.
Complications
Septicemia or blood infection
Meningitis
Optic nerve damage and loss of vision
Endophthalmitis
Endophthalmitis is inflammation of the intraocular cavities caused due to an infection by bacteria,
viruses, fungi and other parasites.
Causes
Infection following penetrating trauma
Infection following intraocular surgery

Signs symptoms
Severe pain
Discharge
Lid edema
Profound decrease in vision
Hypopyon
Absence of fundus glow on distant direct ophthalmoscopy or slit lamp examination
Complications
Infection may spread to the brain and cause meningitis or encephalitis.
Careful history and external examination will help in diagnosing the condition.If a patient has decrease
in vision, lid edema and absence of red reflex following cataract surgery, enophthalmitis should be
ruled out.
Treatment
Include anti-inflammatory agents, antimicrobials and intraocular antibiotics. Systemic and intraocular
routes of medication are used.
Panophthalmitis
Panophthalmitis is inflammation of the entire eye, including tenons capsule. It affects more tissue of
the eye, compared to endophthalmitis. Signs and symptoms are more severe in panophthalmitis.
Treatment is similar to endophthalmitis.
Dacryocystitis
Dacryocystitis is an infection of the lacrimal sac caused due blockage of the nasolacrimal duct.The
bacteria get accumulated in the blocked duct and causes infection. Dacryocystitis may be acute or
chronic.The extent of the blockage can be found by syringing and probing. Cultures may be taken to
identify the type of infection.
Signs and Symptoms
Mostly unilateral
Profuse watering
Tenderness, redness, and swelling in the sac area (acute)
Discharge
Treatment
Acute dacryocystitis – Antibiotic eye drops
Chronic dacryocystitis – Surgery (dacryocystorhinostomy (DCR))

50
Congenital Dacryocystis
Congenital Dacryocystis is common in infants because their tear ducts are not well developed and
block easily.In most of the cases,the problem resolves by the time the child grows to one year of age.
Signs and Symptoms
Mostly unilateral
Profuse watering
Discharge
Treatment
Massage in the lacrimal sac area (between the eye and nose)
Antibiotic drops or ointments for the infection
Syringing and probing, if it persists for several months
○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○

CHAPTER 14
OCULAR TRAUMA
Ocular trauma is one of the most common causes of unilateral blindness in the world. It mostly
affects the people in working age group in developing countries of the world. Ocular trauma
can occurs in a wide range of settings like household, roads, industries, sports etc.
Ocular trauma can be classified as follows:
Blunt injury - The eye wall does not have a full-thickness wound. It is caused by a blunt
object like cricket ball, fist etc.
Penetrating injury - The eye wall has a full-thickness wound a through-and-through injury.
It is caused by a sharp object like pencil, flying objects while chipping the stone etc
Consequences of ocular trauma
Blunt trauma:
Periorbital contusion / Black eye
Orbital Fracture
EOM palsy
Hyphema
Traumatic Iridocyclitis
Angle recession
Lens subluxation or Lens Dislocation
Vitreous hemorrhage
Macular Edema (Berlin’s Edema)
Retrobulbar Hemorrhage
Penetrating trauma:
Lid Laceration
Conjunctival/Scleral perforation
Corneal perforation
Cataract
Examination of a patient with ocular trauma:
In the case of ocular trauma, it is important to know the details of the injury, its mechanism, and time
lapsed after injury. Good history and documentation is important, because, it may be a medico-legal
issue. Decreased in visual acuity, diplopia, swelling, bleeding from the eye should be enquired and
information should be recorded in the case sheet.
Visual Acuity. Measuring visual acuity is essential in all cases for diagnosis, management and medico-
legal reasons.Patients who are unable to read the largest letter on the vision chart should be assessed

52
for counting fingers; if unable to count fingers also then Hand movements close to the face and finally
light perception and projection should be tested with indirect ophthalmoscope.
Lid and Orbit. Assessment of lids for movement, margins, swelling, redness and ecchymosis should
be performed. The lids should be everted to see the presence of foreign bodies. Palpation of the
orbits should be done to rule fractures of the orbit.
Anterior Segment.The sclera,conjunctiva,and cornea should first be evaluated grossly with torchlight
and then with a slit lamp to detect foreign bodies, lacerations, hemorrhage, or swelling. Fluorescein
staining should be done to evaluate abrasions.It should be performed only after the anterior chamber
has been evaluated for flare and cells.
Pupils and Extraocular Movement - RAPD should be checked.Any anisocoria present should be
mentioned.
Extraocular Motility- Uniocular binocular EOM should be examined.The complaint of diplopia
on upward gaze may indicate an orbital floor fracture with inferior rectus muscle injury, edema, or
entrapment.
Posterior Segment. Lens dislocation, vitreous hemorrhage, and retinal detachment should be
ruled out by examining with the direct and indirect ophthalmoscopy with dilated pupils. Ultrasound
B-Scan should be performed, if required.
Intraocular Pressure (IOP). Measurement IOP should be done with applanation tonometer or
Tonopen. IOP should not be measured if there is perforation or penetrating injury.
Chemical Burns
Chemical injuries can occur at workplace, homes, labs etc. The severity of the injury is related to
whether the chemical is alkali or acid-based.Alkali chemicals are more destructive then acidic chemicals
because of their ability to the penetrate tissues.
Consequences of Chemical injuries
• Ischemic necrosis of conjunctiva
• Persistent epithelial defect
• Stromal necrosis thinning
• Corneal perforation
• Raised IOP
Emergency care
If a chemical accidentally falls in the eye, the first step is to irrigate eye with clean running water.
Irrigation of the eye should be continued for about 15-20 minutes and then should be referred to the
nearest health center at the earliest.
In the clinic, the type of chemical concentration should be recorded.The eye should be carefully
examined with slit lamp to determine the extent of the injury and whether there are any foreign
particles imbedded in the eye or under the eyelids.Appropriate treatment should be started based on
the eye condition.
○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○

CHAPTER 15
AMBLYOPIA
Amblyopia is the clinical term for lazy eye.An amblyopic eye is normal structure wise, but visual
acuity is poor.
“Doctor cannot see anything and patient does see anything”
Amblyopia is of various types.
Anisopmetropic amblyopia – It is caused due large difference in refractive error between
both the eyes.
Ametropic amblyopia – It is caused due to high refractive error in both eyes. Hyperopia
has a greater chance of causing amblyopia when compared to myopia.
Stimulus deprivation amblyopia: It is caused due to media opacities, which prevent the
clear image to be formed on the retina. E.g. Congenital cataract, congenital ptosis etc.
Strabismic amblyopia. –It is a caused due misaligned visual axis early in the life.
Amblyopia occurs due to suppressed image or blurred image reaching the brain in early childhood. It
develops between birth and 7 or 8 years of age, the critical period when the eye is in the process of
development. It must be identified and treated before the child becomes 7 or 8 years old, otherwise
the vision loss becomes irreversible.
Treatment
Cycloplegic refraction full correction of refractive error
Removing the cause of stimulus deprivation
Correction of squint
Patching of the good eye
Pharmacological penalization of the non-amblyopic eye using Atropine eye drops.
○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○

54
CHAPTER 16
EYE DROPS AND OINTMENTS
Ocular Infections, inflammation, glaucoma, and many other eye disorders are treated with eye
drops and ointments.Both eye drops and eye ointments have their advantages and disadvantages.
Advantages of eye drops
Does not cause blurring of vision
More products are available
Disadvantages of eye drops
Short contact time
Reflex secretion of tears may dilute the drug
Increased systemic absorption
Advantages of Ointments
Longer contact time
Protect cornea from exposure in cases of lagophthalmos
Most useful in children
Disadvantages of Ointments
Blurred vision following application
More likely to cause allergic reaction
Always remember, eye drops / eye ointments once opened, should be used within one month.
Always write the date of opening of the eye drops/ ointments on the label in the clinic.
Ensure that the cap is closed after the application and tip of the dropper should not touch any
surface.
Always check for expiry date before opening a new bottle of eye drops / ointment

Applying the drops in the eye
First explain the patient that drops will instilled in his/her eye and give some cotton to the
patient.
Wash your hands thoroughly
Request the patient to tilt the head backwards
Create the space for the drops by pulling the lower lid down with an your finger
Put one drop in the space created without touching your eye or eyelid (to prevent
contamination of the bottle)
Block the medial canthus area with your finger for two to three minutes with your finger.This
prevents the drops from traveling down to the lacrimal system and to the rest of the body.
Instruct the patient to wipe the excess drops that is flowing out of the eye with the cotton.
Instruct the patient to keep his eye closed for 2 –3 minutes.
If you want to instill another ye drops, wait at least five minutes before instilling the second
drop.
Wash your hands thoroughly after the entire procedure
○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○

56
CHAPTER 17
MYDRIATICS AND CYCLOPLEGICS
Mydriatics: Dilates the pupil. E.g.- Phenylephrine HCL, Epinephrine
Indications :
Mydriatics are useful for pupillary dilatation for fundus examination.
Mydriatics should not be used in the eyes of narrow angles.
Mydriatics should not be used in the patients with HTN and heart problems.
Phenylephrine HCL is the most commonly used mydriatic agent. It is available in 2.5 % and 10
% drops. (2.5 % is used in infants and elderly patients).
Systemic side effects include HTN, cardiac arrhythmias, headache, myocardial infarction, stroke and
death (rare).
Cycloplegics: Cycloplegics causes paralysis of ciliary muscle also cause dilation of the pupil.
E.g.- Atropine, Homatropine, Cyclopentolate,Tropicamide
Indications :
Useful in controlling pain in iridocyclitis.
Refraction in children
Treatment of amblyopia
In treatment of accommodative esotropia.
·Atropine is the strongest cycloplegic and causes complete paralysis of ciliary muscle. It is
available in the form of 1% e/d and oint.
Cyclopentolate is the most commonly used cycloplegic agent.
Local side effects include raise in IOP, allergy, and corneal toxicity.
Systemic side effects are dry mouth,fever,hallucinations,ataxia,coma,convulsions and even death can
occur.
○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○

Cycloplegic Mydriatic agents
Name of Onset of Duration of Comment
the drug maximum activity
cycloplegia
Atropine sulfate 1% 6-24 hr 10-15 days Not used routinely
except for the
assessment of
accommodative
strabismus and refraction
in children
Homatropine 1hr 1-2 days Not used routinely
hydrobromide
1.25% to 5%
Cyclopentolate 35-45 min 12-24 hr Good rapid-
hydrochloride acting cycloplegic drop for
1%(Cyclogyl) routine use in children in
clinics
Tropicamide0.5 % 23-30 min 4-10 hr Weak cycloplegic agent
Phenylephrine 20-30 min 30 min – hr Does not affect
2.5%(Drosyn) (no cycloplegia) accommodation; helpful
for fundus examination
OPHTHALMIC DYES:
Fluorescein sodium:
Available in the form of strips and solution.
Flourescences yellow green in blue light.
Indications:
Intact corneal epithelium prevents the penetration of the dye, any defect in the epithelium
takes up the stain.
It does not stain devitalised cells and mucus.
Epithelial defects appears bright green and can be easily visualised.
Useful in applanation tonometry.
RGP contact lens fitting assessment.
Seidal’s test – to find out the wound leak following surgery or penetrating injury.
Retinal angiography to examine retinal blood vessels.
It stains soft contact lenses and hence should not be used in SCL wearers.
I.V.Flourescein may cause GI distress, hypotension, temporary yellowish coloration of skin
and urine.
Fluorescein solution may promote growth of pseudomonas.
○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○

58
CHAPTER 18
PRESCRIPTION WRITING
Trade and Generic Name of a Drug:
When a drug is marketed, it is given a specific name that is specific to a pharmaceutical company that
has manufactured it.This is called the trade or brand name of the drug.The name that describes
the chemical composition of the drug is called generic name. A drug can have many brand names,
but only one generic name.
Prescription
A prescription is a written order for preparation, dispensing, and administering drugs to a specific
patient and once the doctor signs it it becomes a legal document
The prescription has four main parts:
The superscription, which consists of the heading where the symbol Rx (an abbreviation for recipe,
the Latin for take thou ) is found.The Rx symbol comes before the inscription.
The inscription is also called the body of the prescription,and provides the names and dosage of the
drug and form of the drug (tablet, eye drops, oint etc.)
The subscription gives specific directions for the pharmacist on how to prepare the medication.
The signatura gives instructions to the patient on how,how much,when,and how long the drug is to
be taken.
The signatura should always be written in simple English, which can be understood by the patient/
attendant. If required, it can also be written in local languages like Telugu. (e.g.“1 tab t.i.d. pc,” should
be written as ,“one tablet three times daily after meals”.
COMMONLY USED ABBREVATIONS IN PRESCRIPTIONS
SYMBOLS MEANING
OD - Right eye (oculus dexter)
OS - Left eye (oculus sinister)
OU - Both eyes (oculus unites
Rx - Prescription / Take thou
H - Hour
Q - Every
Hs - Bedtime (hora somini)
Qs - Quantity sufficient
Tsp - Teaspoon
Ung - Ointment
Bid - Twice a day (bis in die)

SYMBOLS MEANING
Tid - Three times a day (ter in die)
Qid - four times a day (quarter in die)
Q4h - Every 4 hours
Ac - before meals (ante cibum)
Pc - After meals (post cibum)
SOS - Whenever required
○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○

60
COMMONLY
USED
IN
THE
CLINIC
Name
of
the
drug
Brand
names
Category
Purpose
Side
effects
Contraindications
Paracaine
Anesthetic
Applanation
tonometry,
Loss
of
sensation
Allergic
reactions
suture
removal,
syringing

probing
etc
Betametha-sone
Betamet,
milbeta
Topical
steroid
Inflammation,
post
surgery
Delayed
healing,
Infections
Pred
forte
Predinisolone
acetate
increases
susceptibility
to
infections,
can
cause
cataract
and
glaucoma
on
prolonged
use
Flourscein
Strips
-
Dye
Corneal
Epithelial
defects,
Staining
of
Soft
contact
Soft
contact
lenses
in
Applanation
tonometry,
lenses
in
CL
wearers
CL
wearers.
Siedels
test.
Tropicamide
Tropsyin
Weak
cyclopleagic
Pupillary
dilatation
for
Mild
impairment
osf
examining
fundus
near
vision
for
2-3
Shallow
anterior
hours
following
chamber
angle
instillation
Cyclopentolate
e/d
Cyclogic,
cyclopent
Cyclopleagic
Cyclopleagic
refraction,
Pschycosis,
convulsions
Seizure
disorder
0.5
%
-
children

1yr
intraocular
inflammation,
in
small
children
Shallow
anterior
1
%
in
chidren

1
yr
post
cataract
surgery
chamber
angle
Atropine
e/d,
oint
Atroren
Strong
cycloplegic
Refraction
in
small
Fever
Shallow
AC
Angle
children,
amblyopia
treatment
Phenylephrine
HCL
Drosyn
Mydriatic
agent
Pupillary
dilatation
for
Constriction
of
Shallow
anterior
fundus
evaluation
conj
vessels
chamber
angle
Pilocarpine
2%
Pilocar
Miotic,
Anti
–
Before
YAG
PI
Decrease
in
VA
in
Posterior
sub
glaucoma
case
of
central
capsular
cataract
cataract

Tab.Acetazolomide
Iopar
Carbonic
anydrase
All
types
of
glaucomas
Parasethesia,
gastro
GI,
renal
disease
inhibitior
(anti
glaucoma)
intestinal
problems,
renal
stones
IV
Mannitol
-
Hyperosmotic
agent
Immediate
reduction
of
Urinary
retention,
Uncontrolled
BP,
(anti
glaucoma)
IOP,
in
Acute
ACG
cases
Increase
in
BP
Cardiac
diesase
Timolol
0.5
%
e/d
Glucomal
Beta
Blocker
(anti
All
types
of
glaucomas
Bronchospasm
Asthma
glaucoma)
Latanoprost
e/d
-
Prostagladin
(anti
All
types
of
glaucomas
-
-
glaucoma)
Cromolyn
sodium
Allergo,
Ifiral
Anti
allergy
Vernal
conjunctivitis
-
-
Gentamycin,
-
Antibiotics
Conjunctivitis,
keratitis,
-
-
Ciprofloxicin,
post
operative
cases
Vanmycetin
Acyclovir
/
Ocuvir
-
Antivirals
Viral
keratitis
-
-

62
Optics refraction
Module 3

CHAPTER 1
OPHTHALMIC LENSES
Basic concepts
Lenses – Lens is a combination of prisms.They have curved surfaces on one are both the surfaces.
Converging lenses (plus lenses or convex) are thicker at the centre and thinner at the edges.Prism
alignment is base to base.
Diverging lenses (minus lenses or concave) are thicker at the edges and thicker in the centre.Prism
alignment is apex to apex.
Optical centre - Centre of a lens, where the light rays passes through without any refraction.
Principle axis is a line drawn perpendicular to the lens, passing through the optical centre. Rays
passing through the principle axis will go straight without bending.
Principle focal point (F) is a point on the principal axis where light comes to a focus (for a plus
lens) or appears to be diverging from (for a minus lens).
Focal length is the distance between the principal focus and the optical centre of the lens.
○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○

64
CHAPTER 2
OPTICAL COMPONENTS OF THE EYE
The optical components of the eye are
Tear film
Cornea
Aqueous humor
Crystalline lens
Vitreous
Among these cornea and crystalline lens accounts for the most of the refraction that takes place
in the eye hence they are called the major refracting elements of the eye.
Cornea accounts for a power of approximately +43.00D
Crystalline lens accounts for about +17.00 D
Normal anterior surface curvature of the cornea is 7.7mm accounts for a power of +48.00D
Posterior corneal curvature is 6.8mm accounts for –5.0 D together overall power +43.00D.
The more curved the cornea is (steeper) more will be its converging power.
Anterior lens surface curvature of the crystalline lens is approximately 10mm and posterior
lens is 6mm.
Due to the change is anterior lens surface curvature (steepening) the lens will increase its
plus power during accommodation
Refractive index
Cornea 1.376
Tear film,Aqueous Vitreous 1.336
Crystalline lens 1.386
In the eye whenever there is increased refractive index there is high converging power (plus power)
Axial length of the eye
Axial length of the eye is the distance from front vertex of the cornea to the retina. Normal axial
length ranges from 22.0 to 24.0 mm.
○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○

CHAPTER 3
REFRACTIVE ERRORS
Emmetropia: It is a refractive condition where the parallel rays after refraction through the eye
forms a point focus on the retina when accommodation is at rest.
Ametropia: It is a refractive condition where the parallel rays after refraction through the eye will
not form a point focus on the retina when accommodation is at rest.
Myopia: Its is a refractive condition where the parallel rays after refraction through the eye will
form a point focus in front of the retina when accommodation is at rest.
Hyperopia: Its is a refractive condition where the parallel rays after refraction through the eye will
form a point focus behind the retina when accommodation is at rest.
Astigmatism: Its is a refractive condition where the parallel rays after refraction through the eye
will form two lines instead of a point focus accommodation is at rest.
○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○

66
CHAPTER 4
MYOPIA
Myopia is the refractive condition of the eye in which the parallel rays of light come to a focus
on a point in front of the retina when accommodation is at rest. Myopia is usually detected at
the age of 8-10 years and keeps increasing till mid-teens when it stabilizes at less than -6.0 Dsph.
CLASSIFICATION:
Axial myopia
Curvature
Index myopia
Axial myopia:
- Myopia due to increase in axial length of the globe is called as axial myopia.In axial myopia,the
eye is relatively long for its refractive status. (24mm axial length).
Curvature myopia :
- Curvature myopia occurs when the curvature of cornea becomes more curved than the
normal.As the curvature of the cornea increase,the image is focused further in front of retina
Curvature myopia can be seen in cases of keratoconus.
Index myopia :
- Index myopia is caused due an increase in refractive index of lens or cornea.As age increases
the refractive index of lens also increases. Index myopia can be seen in cases of nuclear
sclerosis.
Myopia Corrected Vision

Simple Myopia
Most common
Appears in early teens and remains stable or increases minimally
Less than 6.0 D
No retinal changes
Pathological or Progressive myopia:
Rare form of myopia
Appears at younger age
Greater 6.0 D
May increase at a rate of up to 2.0 to 3.0 D per year
Associated with chorio-retinal degeneration
Stabilizes at the age of 20 year but can progress beyond 30 years
Signs Symptoms
Blurred vision for distance
Squeezing of eyes to see the distance objects
Prominent large eyes ( high myopia)
Treatment Options
Spectacles (Glasses): Concave lenses
Contact lenses
Refractive surgery:The central cornea is made flatter by making incisions or by laser.This will
be a decrease in the corneal power. Eg. LASIK
○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○

68
CHAPTER 5
HYPEROPIA
It is defined as a refractive condition of the eye where parallel rays come to focus behind the retina
when accommodation is at rest.
CLASSIFICATION:
Axial Hyperopia
Curvature Hyperopia
Index hyperopia
Axial Hyperopia
- The axial length is less than the normal ( 24mm). Eg. microphthalmos
Curvature Hyperopia
- It is due to change in corneal curvature or change in curvature crystalline lens.
Eg. Cornea plana.
Index Hyperopia
- It Occurs due to a decrease in the index of refraction (and density) in any part of the optical
system of the eye
Classification of Hyperopia based on accommodation status
Facultative Hyperopia: The amount of hyperopia that can be corrected by the patient’s
accommodative effort.
Absolute Hyperopia:After using accommodation the remaining uncorrected hyperopia.
Manifest Hyperopia:The total amount of hyperopia after paralyzing the of accommodation.
Hypermetropia Corrected Vision

Latent Hyperopia: The amount of the hyperopia is corrected by the tone of ciliary muscle.
Total Hyperopia: The hyperopia estimated under complete cycloplegia.
As age increases, the accommodative power of the eye decreases.This will cause a shift
from latent hyperopia to absolute hyperopia
Signs Symptoms
Asthenopia: fatigue, eye strain on prolonged near work
Headache
Poor near vision
Shallow anterior chamber (in case of high hyperopia)
Treatment Options
Glasses: Convex lens
Contact lenses
Refractive surgery
○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○

70
CHAPTER 6
ASTIGMATISM
It is a refractive condition where parallel rays coming from infinity after refraction form two lines
instead of a point focus on the retina when accommodation is at rest. This is due to change of
curvature in the different meridians.
Regular Astigmatism:
There is a different refraction in two meridians, which are at right angle to each other. It can be
corrected by regular spectacle lenses.
With the rule (WTR): In this condition vertical corneal curvature is more than horizontal
curvature.
Minus cyl axis at 180 (+/- 30) or Plus + cyl axis at 90 (+/- 30)
Against the rule (ATR): In this condition the horizontal corneal curvature is more than the
vertical curvature.
Minus cyl at 90( +/-)30 or Plus cyl at 180 (+/- 30)
Irregular Astigmatism:
Different meridians have different curvature and they are not at right angles to each other.This error
cannot be neutralized during retinoscopy nor can corrected using glasses. Eg. Keratoconus
○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○

Oblique astigmatism:
It is regular astigmatism where two-principle meridians are at oblique still at right angle to each other.
Astigmatism can further be classified in to 5 types as following.
Simple myopic astigmatism : It is refractive condition of the eye where the parallel rays
coming from infinity form one focal line in front of the retina and other on the retina when
accommodation is at rest.
Eg: Plano -2.00Dc x 180
Simple hyperopic astigmatism : It is a refractive condition of the eye where the parallel
coming from infinity form one focal line behind the retina and other on the retina when
accommodation is at rest.
Eg: Plano +0.50Dc x 90
Compound myopic astigmatism: It is refractive condition of the eye where the parallel
rays coming from infinity form two lines in front of the retina. when accommodation is at rest.
Eg:–2.00D/-2.00Dc x 180
Compound hyperopic astigmatism:It is refractive condition of the eye where the parallel
rays coming from infinity form two lines behind the retina when accommodation is at rest.
Eg: +1.00D/+1.00D cyl x 180
Mixed astigmatism: It is refractive condition of the eye where the parallel rays coming
from infinity and form one focal line in front of the retina and other focal line behind the
retina when accommodation is at rest.
Eg: +1.00D/-2.00D cyl x 180
Correction Options
Spectacle lenses - Cylindrical lenses
Contact lenses (RGP Lenses)
Refractive surgeries
○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○

72
CHAPTER 7
PRESBYOPIA
Presbyopia: presby (old) + opia (vision)
Presbyopia is a term used to describe the condition in which a patient’s amplitude of accommodation
has decreased to a point where clear / comfortable vision at the near point is difficult.
The amplitude of accommodation gradually decreases with age. Presbyopia generally occurs when
the patient’s amplitude of accommodation is less than 5 D.At this point the patient is required to use
more than half their amplitude of accommodation at the near point and this will result in symptoms.
The age of onset of presbyopia is variable. In India, presbyopia occurs around the age of 38-39 years.
It occurs earlier in patients with hyperopia. It is important to differentiate latent hyperopia from
presbyopia in patients around 36-38 years.
Signs Symptoms
Blurred vision at the patient’s normal reading distance
Eyestrain on prolonged reading
Complaints of fatigue with reading
Decreased Amplitude of Accommodation
The factors determine the need for correction of presbyopia are
Distance refractive error
Amplitude of accommodation
Occupation
Special near vision demands
Correction of Presbyopia
Bifocals ( Kyrptok, Executive, D-bifocals )
Single near vision glasses for near
Progressive addition lenses
The power which is prescribed for correction of presbyopia is called add or addition. Addition is
given on top of the refractive correction of the patient for at distance. When we perform lensometry
of a bifocals, the difference between the near power and distance power will give the add. Add is of
same power in both the eyes in most of the cases.The maximum addition that can be given in spectacles
is +3.50 D.

Determination of Add Power
Based on amplitude of accommodation
• The patients need to have ½ to 1/3 of their accommodative amplitudes as reserve to have
comfortable range.
• Add Power = 1/working distance (meters)-1/2(amplitude of accommodation)
Based on age of the patient
It is based on assumption that all individuals of the same age have the same amplitude of accommodation.
(Which is not always true).
AGE (yrs) Add (D)
38 +0.75
40 +1.00
45 +1.50
50 +2.00
55 +2.50
60 and above +3.00
Treatment Options
Single vision glasses for near
Bifocals
Progressive addition lenses
○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○

74
CHAPTER 8
OBJECTIVE REFRACTION
Refraction is a clinical technique used to obtain an objective measure of the refractive status of the
eye. Objective refraction is performed using an instrument called retinoscope.The retinoscope
projects a beam of light into the patient’s eye through the pupil.Through the peephole in the retinoscope,
the observer sees the retinal light reflex coming from the patient’s pupil.By observing the behavior of
the reflex, the observer can objectively determine the refractive error of the patient’s eye.
A retinoscope consist of an optical head, a sleeve, and a battery handle.The optical head projects a
streak of light from one side and it has a peephole on the other side. The streak of light to be
converged or diverged by moving the sleeve up or down.The sleeve can also be rotated to change
the orientation of the streak.
Static retinoscopy - Refraction that is performed, while the patient fixates at t
distance object (Accommodation is in relaxed state).
Dynamic retinoscopy – Refraction is performed, while the patient fixates on an
object in the plane of the retinoscope. (Accommodation is in active).
Cycloplegic retinoscopy - Refraction is performed, after the ciliary muscle is
paralysed using cycloplegic drops. (Accommodation is paralysed). (Accommodation
is in active).
Procedure
Working Distance
The distance between the patient and the observer, while performing refraction is called a
working distance. Normally it is 66cm (+1.50D) or 50cm (+2.00D).This is called working
distance lens.
Fixation Target
The target given for the patient should be large letter (20/400 or 20/200 letter).The target
should not stimulate accommodation.
Instructions for the patient
The patient should be instructed to fixate the distance target.
The patient’s right eye should be examined with the examiner’s right eye and vice versa.This
allows the examiner to stay as close to the patient’s visual axis as possible.
The examiner should not obstruct the patient’s view of the target.The patient should be
instructed to tell the examiner if the view of the target is blocked.

Examine the four primary meridians (90, 180, 135, and 45 degrees) by moving the streak
along each of these meridians.With no lenses in the trial frame there are three possible reflexes that
may be observed:
With Motion, the patient is hyperopic, emmetropic or less myopic than the dioptric value of the
distance.
Neutrality, the patient’s myopia is equivalent to the dioptric value of the working
distance.
Against Motion, the patient’s myopia is greater than the dioptric value of the working distance.
First identify the meridian with the most with motion.This meridian should be neutralized
firsby using plus spherical lenses.
Then rotate the streak by 90 degrees and look for the movement.There are 2 possiblities –
Against movement or No movement.
If against movement is seen, then it is suggestive of a cylindrical power and it should be
neutralized by using minus cylinder lens.
If no movement is seen, then the meridian is neutralized.
Characteristics of the reflex
Brightness of the Reflex
As we move closer to neutrality, the illuminated area of the retina becomes smaller.This
increases the amount of light reflected from the retina and the reflex to appear brighter to
the examiner.

76
Neutrality
When the patient’s far point is at the peephole of the retinoscope, no movement is seen.
Whole pupil will be filled with light.This is the end point of refraction.
The width and the speed of the reflex as it moves across the pupil give an indication of how
far we are from neutrality.
Recognizing the presence of astigmatism
If one meridian has against motion and streaking the meridian 90 degrees away shows with motion,
then it indicates presence of astigmatism.
Clues that can be used to recognize astigmatism:
The Thickness Phenomenon
The Intensity Phenomenon
The Break and Skew Phenomena
Straddling the Axis

The Thickness Phenomenon: The streak reflex appears to be narrowest when we are in the
meridian of the correct axis. As we move away from the correct axis, the streak reflex becomes
wider.
The Intensity Phenomenon: The streak reflex appears brightest when we are on the meridian of
the correct axis.As one move away from the correct axis, the streak reflex becomes dimmer.
The Break and Skew Phenomena: In cases of high astigmatism, the streak reflex will tend to stay
on-axis even if the streak is rotated off-axis.This guides you back to the correct axis.
The skew phenomenon: If we streak a meridian that is away from the correct axis, the streak
reflex will tend to travel along the correct meridian rather than follow the streak.This guides us back
to the correct meridian.
Straddling the Axis: If there is regular astigmatism, when one meridian has been neutralized, the
meridian exactly 90 degrees away will have the strongest, most defined reflex. The axis can be
confirmed by streaking the meridians 45 degrees to each side of what we expect to be the meridian
of the correct axis.

78
E.g.: If the cylinder is present at 90 degrees. We streak the 45-degree meridian and 135-degree
meridian.The width and brightness of the streak reflex will be same.Similar thing happens when we
streak the.This confirms 90 degrees as the correct meridian.
If the reflex in one of the meridians is narrower than the reflex in the other, then the estimated axis
should be adjusted in the direction of the meridian with the narrower reflex.We would retest 45
degrees to each side of the new axis to confirm that the reflex in each straddle meridian is equally
wide.
Final power
If you get hyperopic error, subtract working distance lens from the spherical value that is
obtained in the refraction, leaving the cylindrical value unchanged.
E.g. If reflex is neutralized with + 5.0 sph / -1.0 cyl @ 90, working at 50 cms.Then final
refraction value will be +3.0 sph / -1.0 cyl @ 90.
If you get myopic refractive error, add the working distance lens to the spherical power
obtained, leaving the cylindrical value unchanged.
E.g. If reflex is neutralized with - 5.0 sph and -1.0 cyl @ 90, working at 50 cms.Then final
refraction value will be -7.0 sph/ -1.0 cyl @ 90.
Always record your findings in minus sphere-cylinder form.
Sources of error during retinoscopy
Incorrect working distance
Scoping off the patient’s visual axis
Failure of the patient to fixate the distance target
Failure to obtain reversal of the movement
Failure to locate the principal meridians

Manual retinoscopy Vs auto-refractor
Manual retinoscopy needs many hours of practice before one can master the technique. A good
refractionist can examine both eyes in less than a minute.
Auto-refractors need much less practice and skill.They are faster but can give wrong reading when
there is there are irregularities and opacities (e.g. corneal edema, cataracts) of the ocular media.
The advantage of manual retinoscopy is that we can visualize the media irregularities (by the behavior
of the reflex) and can recognize the conditions that may compromise the refraction.
Auto-refractors may overestimate myopia and underestimate hypermetropia in children young
adults.This can be avoided by doing cycloplegic refraction.
○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○

Lv book (1).pdf

Recommended

Recommended

More Related Content

What's hot

What's hot (20)

Similar to Lv book (1).pdf

Similar to Lv book (1).pdf (20)

Recently uploaded

Recently uploaded (20)

Lv book (1).pdf