Eye

3. EYE
• Human eyeball is approximately globe shaped
with diameter of about 24 mm.
• Eyeball is situated in bony cavity known as
orbital cavity or eye socket.
• Eyeballs are attached to orbital cavity by
occular muscles.

4. Muscles of Eyeball
Intrinsic (Smooth muscle fibres)
• 1. Constrictor pupillae
• 2. Dilator pupillae
• 3. Ciliary muscles
Extrinsic (Skeletal muscle fibres)
• 1. Superior Rectus
• 2. inferior rectus
• 3. Medial Rectus
• 4. lateral Rectus
• 5. Superior oblique
• 6. Inferior oblique

5. Accessory Structures
• EYELIDS – Protect eye ball from foreign particles
coming in contact with its surface.
• CILIA (EYE-LASHES) – Margins of eyelids have
sensitive hairs called cillia. Meibomian glands and
Sebaceous glands open into fillicles of cilia.
Infection of these follicles lead to development of
common disorder of eye called Stye.
• EYEBROW – Protect eyes from foreign bodies
entering eyeball.

6. Conjunctiva
• Thin membrane that covers exposed part of eye.
• Part of conjunctiva covering eyeball is called as
bulbar portion and part covering eyelid is
palpebral portion.
• Surface of conjunctiva lubricated by thin film of
tears secreted by lacrimal gland.
• Due to its continuous washing and lubrication,
conjunctiva is kept moist and protect from
infection.

7. Walls of Eyeball
• Composed of 3 layes
• 1. outer layer – cornea and sclera
• 2. middle layer – coroid , ciliary body & iris
• 3. inner layer – retina

9. Outer layer
• Outer layer preserves shape of eyeball . The
posterior 5/6th of this coat is opaque and is
called sclera. The anterior 1/6th is transparent
and is known as cornea.
• SCLERA – 1. formed by white fibrous tissue
and elastic fibres.
2. sclera is pierced by optic nerve.

10. • Cornea – 1. transparent, but it does not
appear transparent, it appears in different
colours such as blue, green, brown, grey,
black. It is because colour of iris which is
present just behind cornea.
2. Junction of sclera and cornea is called as
Limbus.
3. cornea is avascular structure.

11. • 4. derive its nourishment from aqueous
humor.
• Very sensitive to pain, touch, pressure, cold.

12. Middle layer
• It surrounds eyeball completely except for a
small opening in front known as pupil. It
comprises 3 structures
• 1. Choroid 2. Ciliary body 3. Iris

13. • CHOROID – forms posterior 5/6th of middle
layer. Separated from sclera by perichoroidal
space.
• CILIARY BODY – middle layer is thickened to
form ciliary body; it is in form of ring.
Suspensory ligaments from lens are attached
to ciliary body. Anterior surface of cilliary body
faces towards centre of cornea.

14. Iris
• Coloured structure and forms anterior most part
of middle layer.
• Thin circular diaphragm placed in front of lens.
• It has circular opening in centre called “pupil”
• It is muscular structure and has 2 muscles.
1. constrictor pupillae
2. dilator pupillae
• Iris acts like diaphragm of camera. It regulates
amount of light entering the eye by altering
diameter of pupil.

15. Retina
• Innermost layer, continues posteriorly with
optic nerve
• It has receptor of vision i.e., rods & cones.
• Opposite the entrance of optic nerve, there is
circular area called as “optic disc”. It is 1.5mm
in diameter.

18. RODS & CONES – light receptor of eyes.
Respond to dim light and bright light.
• Rods and Cones are the photoreceptors,
useful in providing vision to the eyes.
• Rods provide vision during dim light or night
also known as scotopic vision,
whereas cones provide vision during day time
or at bright light also known as photopic vision

19. • Rods are responsible for vision at low light
levels (scotopic vision). They do not mediate
color vision
• Cones are active at higher light levels
(photopic vision), are capable of color vision
and are responsible for high spatial acuity.

21. • Anterior margin of retina forms a wavy line
called as ora serrata.

23. • Depressed area of optic disc is called
physiological cup. It has no rods and no cones,
and hence insensitive to light (physiological
blind spot)
• The place in the visual field that corresponds
to the lack of light-detecting photoreceptor
cells on the optic disc.

25. • 3 mm lateral to optic disc, another depression
is there known as “macula lutea”., avascular
and yellow in colour, centre of macula form
“fovea centralis” and it is thinnest part of
retina, contains cones only

27. 10 layers of Retina
• 1. the outer pigmented layer
• 2. layer of rods and cones
• 3. External limiting membrane
• 4. Outer nuclear layer
• 5. outer plexiform layer
• 6. inner nuclear layer
• 7. inner plexiform layer
• 8. Ganglion cell layer
• 9. nerve fibre layer
• 10. Internal limiting membrane

29. Intraocular fluid
• 2 types of fluids are present
1. Vitreous humor
2. Aqueous humor
1. VITREOUS HUMOR – lies between lens and
retina.
Helps to maintain shape of eyeball.

30. 2. AQUEOUS HUMOR – Lies between lens and
cornea.
Formed by cilliary processes.
• Maintain shape of eyeball, intraocular
pressure, provide nutrients, Oxygen and
electrolytes to avascular structures like lens
and cornea, removes metabolic end products
of lens and cornea.

33. LENS
• Crystalline in nature and situated behind
pupil.
• Biconvex, transparent and possesses elastic
property.
• Supported by suspensory ligament which is
attached to cilliary body.
• In old age, lens become opaque and this
condition is called cataract.

34. • helps to refract light to be focused on the retina.
• by changing shape, functions to change the focal
distance of the eye so that it can focus on objects
at various distances, thus allowing a sharp real
image of the object of interest to be formed on
the retina. This adjustment of the lens is known
as accommodation
• is similar to the focusing of a photographic
camera via movement of its lenses.
• The lens is more flat on its anterior side than on
its posterior side.
• In humans, the refractive power of the lens in its
natural environment is approximately
18 dioptres, roughly one-third of the eye's total
power.

35. • Artificial lenses are made of inert (or non-
reactive) materials, such as PMMA
(Polymethyl methacrylate), silicone, and
acrylic. Just like natural lenses, artificial
lenses have refractive power, or the ability to
bend light, which helps to focus light rays and
images on the retina.

36. CLINICAL ANATOMY
• Cornea can be grafted from one person to another.
• GLAUCOMA – over production of aqueous humour or
lack of its drainage or combination of both leads to
disease.
• Central artery of retina is end artery.
• Optical defects include myopia (short- sightedness),
hypermetropia (long- sightedness)
• Inflammation of conjunctiva leads to conjunctivitis.
• Palpebral conjunctiva is used to judge Hb level.