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1. WOLLEGA UNIVERSITY INSTITUTE
OF HEALTH SCIENCES
Hunduma Gelalcha
(Optometrist)
December 2019

2. NO FINANCIAL DISCLOSURE
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3. INTRODUCTION TO ANATOMY AND PHYSIOLOGY OF THE
EYE
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4. Outline
1.1. THE PROTECTION OF THE EYE
1.2. THE EXTRAOCULAR MUSCLES
1.3. THE EYEBALL (GLOBE)
1.4. VISUAL PATHWAY
1.5. BLOOD SUPPLY, LYMPHATIC DRAINAGE and NERVE SUPPLY of EYE
and ADNEXA
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5. Objectives
• Describe the basic anatomy of the eye and surrounding structures
• Explain the correlation between anatomy and physiologic function of
the eye and adnexal structures
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6. 1.1.THE PROTECTION OF THE EYE
 Structures involved in the protection and support of the eye Include:
Orbital bones
Eyebrow
Eyelids
Conjunctiva
The Lacrimal Apparatus (and Tear Film)
6

7. ORBITAL BONES
• The orbit is formed of 7 bones and has 4 walls
• Orbital Walls:
– Roof- Frontal bone and Sphenoid bone
– Floor- Zygomatic, Maxillary and palatine bones
– Medial- Ethimoid, Frontal, Lacrimal and Sphenoid bones
– Lateral-The strongest of all walls- Zygomatic and Sphenoid bone
• The orbital walls provide protection, support and passage routes for
vessels and nerves to the eye and adnexa
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8. Orbital Bones
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9. THE EYELIDS
Gross Anatomy- overview
 Have complex structure to allow their various functions
 Have Anterior and Posterior lamellae, marked by the Gray line
 Anterior- Skin, Muscle, skin Glands
 Posterior- Tarsal plate, Conjunctiva, Glands
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10. Eyelids
3 Structurally important parts of the eye lid
I. Skin
II. Muscles
III. Tarsal plate
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11. 1. Eyelid Skin
• is amongst the thinnest and most mobile skin in the body
• receives its sensory innervations from the first and second divisions
of the trigeminal nerve
• Little or no subcutaneous fat under the skin which makes it to be
good source for skin graft
• Has an extremely good blood supply that is why wound heals well
and quickly.
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12. 2. Eyelid Muscles – Eyelid Protractors
• Orbicularis Oculi muscle
– It lies between the skin and tarsal plate; it circumferentially
surrounds the Palpebral fissure
– It serves to close (Protract) the upper and lower lids
– It also assists in the function of the lacrimal pump system
– It is innervated by the Facial (7th cranial) nerve
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13. 2. Eyelid Muscles- Eyelid Retractors
Levator Palpebrae Muscle and Aponeurosis
• The Levator shares a common origin (sheath)and nerve supply
(Oculomotor nerve) with the superior rectus
• The distal tendinous part is referred to as the Levator aponeurosis.
• the major eye lid elevator
13

14. Muller’s Muscle
 originates from the undersurface of the Levator and inserts into the
superior border of the upper lid tarsus
 It is composed of sympathetically innervated smooth muscle fibers
and provides 2 mm of additional elevation of the upper eyelid
The lower eyelid retractors consist of the Capsulopalpebral Fascia
and the Inferior Tarsal Muscle
 arise from the Inferior Rectus muscle sheath and insert into the
inferior tarsal border, skin , orbicularis and orbital septum
 Also includes a ligamentous part that supports the globe
 innervated by Oculomotor and sympathetic nerves
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15. Orbital septum- found deep to the orbicularis oculi and serves as a
barrier to the posterior extension of preseptal fluid and as a
partial barrier to the spread of preseptal infection.
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A. Sagittal section of Asian eyelid anatomy. B. Sagittal section of Caucasian
eyelid anatomy.

16. 3. Tarsal Plate
• Composed of dense connective tissue and provides support for the
lid (Keep the eye lids rigid and firm)
• Contains Meibomian glands, which open at lid margin releasing an
oily secretion that forms part of corneal tear film
• The upper lid tarsus is 8 to 12 mm high, whereas the lower lid tarsus
is only 3 to 4 mm high
• The tarsal plates of the upper and lower lids contain approximately
30 to 40 and 20 to 30 Meibomian glands, respectively
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17. THE CONJUNCTIVA
• The conjunctiva is a continuous lining extending from the
mucocutaneous junction of the lid margin, across the
fornix, and up to the corneal limbus.
• The main function of the conjunctiva is to protect the
cornea.
– During opening and closure of the eyelids, it lubricates
the cornea with tears.
– Mucin from goblet cells has wetting effect of tear film
– Also secrets tear from accessory lacrimal glands
– In addition to acting as a physical barrier, it houses
immune cells and its substantia propria is highly
vascular.
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18. It has three parts:
• I. Tarsal Conjunctiva- part lining the inner aspect of the eye lid and
firmly adherent to the tarsal plate
• II. Bulbar Conjunctiva - part lining the eye ball
– Loosely attached to the underlying sclera
• III. Fornix (Forniceal)- part in which the tarsal and bulbar conjunctivas
are continuous
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19. The Protection of the Eye - Conjunctiva
19

20. THE LACRIMAL APPARATUS
Consists of:
 Lacrimal glands (Main and accessory glands)
 Lacrimal Punctum (upper and lower)
 Lacrimal Canaliculus (Common, upper and lower)
 Nasolacrimal sac
 Nasolacrimal duct
 The main function of the lacrimal apparatus is to produce, secret and drain tear,
which is essential for ocular health and visual function
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21. THE TEAR FILM
 Tear forms a thin film of fluid on the surface of the conjunctiva and
cornea, which is vital for the health, and transparency of the cornea
The Tear film is composed of 3 layers
1. Outer layer (Lipid layer)- oily produced by the sebaceous glands of
the eyelid (Mebomian and Zeis glands) and Caruncle
2. Middle layer (Aqueous layer)- Water from Lacrimal gland and
accessory lacrimal glands of Krause and Wolfring.
3. Inner part (Mucin layer)- Mucus from goblet cells of the conjunctiva
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22. Tear Film
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23. Functions of the tear film
1. Provides moist environment for the surface epithelial cells
of the conjunctiva and cornea
2. Along with the lids (in contact with the tarsal conjunctiva),
it washes away debris and shed corneal epithelial cells
3. Transport metabolic products (oxygen, carbon dioxide) to
and from the surface cells
4. Antimicrobial actions (contains immunoglobulin's )
5. Provides a smooth refracting surface over the cornea (a
normal tear film is necessary for proper refraction of light
by the cornea)
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24. 1.2. THE EXTRAOCULAR MUSCLES
 In humans there are six oculorotary muscles (called
EOMs), functioning as antagonist pairs (1 EOM of a pair in
each eye)
 The Extraocular Muscles (EOMs) originate from the
orbital bones inside each orbital cavity and insert onto
the sclera
 Their actions combine to result in the complex movement
types and directions of the eye
 The site of origin, course in the orbit and site of Scleral
attachment determine their action on eye movement
 The actions of the EOMs are complex and generally
depend on the starting eye orientation
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25. 25

26. Eye Movements:
• Duction:- refers to movement of one eye and is
accomplished by simultaneous and equally graded
contraction and relaxation of antagonistic muscles
• Version:- refers to simultaneous movement of both
eyes in the same direction
• Vergence- is the simultaneous and equal movement
of the eyes in opposite directions
• Torsional movement of the eye about the
anteroposterior axis is expressed with respect to
the displacement of the superior pole of the eye as
in/out.
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27. THE EYEBALL (GLOBE)
• The globe is highly complex in terms of its own three-dimensional
shape and because of the number of other anatomic elements
contained within it and surrounding it (Ocular Adnexa).
• In addition, a number of vascular and neural structures pass into and
out of the globe, further complicating its topography.
• To adequately understand the globe as an organ of vision, it is first
necessary to understand its structure and the complex
interrelationships that exist between its internal organization and the
external elements surrounding it (ocular Adnexa).
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28. The Eyeball (Globe) – Topographic Overview
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Relation to Adnexal soft tissue, Orbital bones and paranasal sinuses

29. The Eyeball (Globe) – Wall and inner Structure
• The eyeball can be considered as having Wall with 3 layers:
1. Outer (coat): a tough layer of fibrous tissue made up of the
Sclera and Cornea
2. Middle: a vascular layer (Uvea) made up of the Iris, Ciliary body
and Choroid
3. Inner: a neural layer made up of the Sensory Retina and Retinal
pigment epithelium
• The inside of the globe can be considered to have 3 Spaces:
1. Anterior Chamber – filled with Aqueous Humor
2. Posterior Chamber – filled with Aqueous Humor
3. Vitreous Space – filled with Vitreous Humor
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30. The Eyeball (Globe) - Wall and inner Structure
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31. Outer Wall-Layer (Coat)
THE SCLERA:
Normally Opaque and seen externally as White
 Is a tough structure of dense fibrous tissue, covers five-sixths of the
outer tunic of the eye
 Is relatively avascular gets its metabolic demand by diffusion from the
vascular Uvea and Episclera
 Contains openings and canals for the various vessels and nerves
entering and exiting the globe
 Its mechanical properties and limited distensibility help contain the
intraocular pressure and prevent deformations of the globe during
extraocular movement
 Provides sites of attachment to extraocular and ciliary muscles and
supports the optic nerve fibers exiting the eye
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32. THE CORNEA:
• Normally clear (transparent)
• Is a tough transparent and avascular tissue
• Obtains its metabolic needs from vessels at limbus and aqueous
fluid, and oxygen from atmosphere
• Along with the Precorneal tear film, it forms the major refracting
surface (75 %) for the eye
• The external dimensions of the cornea in adults are 11.6 to 12.6
mm horizontally and 10.6 to 11.7 mm vertically
• Thickness varies between 0.5mm centrally to 1 mm peripherally at
the limbus (Corneo- scleral junction)
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33. The Cornea:
• Has very rich sensory nerve supply from ophthalmic branch of trigeminal
nerve
• The optical zone of the cornea is the central one-third, approximately 4mm
in diameter
• The corneoscleral limbus is the circumferential zone that contains the
transition of corneal to sclera
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34. 34
The Cornea: Layers

35. Corneal Endothelial Cells
• can’t regenerate but can expand to fill gaps left by damaged cells
• Act as a membrane to prevent excess flow of fluid into the cornea
and actively transport fluid out of the stroma to keep the corneal
water content normal
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36. THE MIDDLE WALL LAYER (UVEA)
 Is a Vascular layer Consisting of the Iris, Ciliary body and
Choroid
 They are continuous with one another and are collectively
known as the Uveal tract (Uvea in Latin means grape)
 Almost the entire blood supply of the eye, Except for the inner
retina, comes from the uveal vessels
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37. • is the anterior extension of the Uvea that forms a mobile diaphragm
between the posterior chamber and anterior chamber of the eye
• extends transversely in a radial direction from the center of the eye
to join the ciliary body
• The central aperture of the iris forms the pupil, through which light
enters the eye
• The diameter of the pupil varies from 1.5 to 8 mm, it is regulated by
movement of the iris, thus impacting the amount of light that enters
the eye
– Pupil Size also depends on: Age, Sleep, Emotional state, alcohol intake
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THE IRIS:

38. • The anterior surface of the iris is visible through the cornea and is
separated from the cornea by the anterior chamber
• Its posterior surface faces the posterior chamber and is in contact
with the anterior surface of the lens at its central portion
38
The IRIS:
Pupillary portion of the iris.

39. The IRIS:- has two smooth (Involuntary) muscles
1. Constrictor Pupillae - located over a 1mm wide area, Concentrically
around the pupil
◦ supplied by Parasympathetic fibers from the Oculomotor nerve
(Cranial nerve III)
◦ Stimulation of the muscle causes constriction of the pupil (Miosis)
2. Dilator Pupillae - found radially extending from the ciliary body to
the Constrictor Pupillae
◦ innervated by Sympathetic fibers from the Superior Cervical
Ganglion
◦ Stimulation results in pupillary dilation (Mydriasis)
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40.  The anterior chamber represents an area bordered:
• anteriorly by the posterior surface of the cornea
• Posteriorly by the anterior surface of the iris and the pupillary portion of
the lens, and
• peripherally by the trabecular meshwork, scleral spur, ciliary body, and
iris root, which comprise the anterior chamber angle (ACA)
• AC depth varies based on refractive error, age, sex, ethnicity,
genetics, and the amplitude of accommodation
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The Anterior Chamber (AC) and Aqueous Humor:

41. • The anterior chamber contains aqueous humor
– This is a crystal-clear fluid secreted by the Ciliary body
– The index of refraction of this fluid is 1.3336 and is less than that
of the lens, which is 1.39
• The balance between the rate of aqueous production and outflow
determines the intraocular pressure.
• The aqueous humor provides nutrients for the avascular lens and
cornea and takes away waste products from these structures
41
The Anterior Chamber (AC) and Aqueous Humor:

42. 42
• The ciliary body is a somewhat triangular (in meridional
sections) middle part of the uvea composed of thepars
plicata and the pars plana
• Extends from the scleral spur (SS) to the Ora Serata (OS)
• The Pars plicata is the site of aqueous secretion and
zonular (Z) attachment with the lens
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Ciliary Body (CB):
Anterior view-CB and Z
Posterior view-CB and OS ACA, CB and Z

43. can be divided into four layers:
• Epithelial layer
• Stroma,
• Ciliary muscle, and
• Supraciliary space
43
The Ciliary Body (CB):

44.  The ciliary body has three basic functions:
◦ aqueous production and removal
◦ Accommodation for near vision
◦ formation of vitreous Mucopolysaccharide
 The arterial supply to the ciliary body is via the long posterior ciliary
and anterior ciliary arteries
 Venous drainage is into the Choroidal vasculature and vortex veins
 Innervation:
◦ Mainly parasympathetic to the ciliary muscle
44
The Ciliary Body:

45. • It is an irregular-shaped space containing aqueous fluid
• It is bounded:
– anteriorly by the posterior surface of the iris
– centrally by the lens capsule
– peripherally by the ciliary body and iris
– Posteriorly by anterior vitreous face
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THE POSTERIOR CHAMBER:

46. • The lens is a transparent biconvex structure located
posterior to the iris and the pupil and anterior to the
vitreous body
• It Consist of Epithelial cells and tightly packed transparent
Fiber cells enclosed in an elastic capsule
• Has three anatomical parts: Capsule, Cortex, Nucleus
• It is Avascular and its nutrition is maintained by the
metabolic exchange between itself and the aqueous humor
• The lens measures approximately 10 mm in diameter and 4
mm in thickness in adults
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THE LENS:

47. Relations in the Anterior segment
47
THE LENS:

48. Structure and parts of the lens
48
THE LENS:

49. • The choroid is a highly vascularized and pigmented tissue which is
the posterior extension of the ciliary body
• It extends from the Ora Serrata anteriorly to the optic nerve
Posteriorly
• It is a network of blood vessels arranged into layers with the
arteries and veins located externally while capillaries are found
internally
• It has pigment cells (Melanocytes) that absorb light to prevent
unwanted reflection and give it a dark brown coloration
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THE CHOROID:

50. • It is responsible for most of the blood supply of the retina
• The blood supply to the choroid is extensive, being provided by the
long posterior ciliary arteries, the short posterior ciliary arteries, and
the anterior ciliary arteries
• The venous drainage of the choroid is via the vortex veins
50
THE CHOROID:

51. The Inner Wall-Layer (RETINA)
 The retina is a very thin, delicate, and transparent membrane, that
extends over the inner surface of the eye from the Optic Disc
Posteriorly to the Ora Serrata anteriorly
 It consists of two distinct layers: the Neurosensory retina and the
Retinal Pigment Epithelium (RPE)
 It is loosely attached to the choroid via the RPE
 Anteriorly, the RPE becomes continuous with the pigmented
epithelium of the ciliary body and the Neurosensory retina becomes
continuous with the non-pigmented epithelium of the posterior layer
of the ciliary body
 It is thickest at the optic disc, measuring 0.56 mm in thickness and
becomes thinner peripherally
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52. • is the most external layer of the retina
• It consists of a uniform layer of single cells and extends
from the optic disc to the ora serrata
• Plays an important role in:
– transport of nutrients and metabolites through the
blood–retinal barrier
– metabolism of photoreceptor outer segments
– absorption of scattered light
– turnover of vitamin A
52
THE RETINAL PIGMENT EPITHELIUM (RPE)

53. 53

54. MACULA:
• Point of sharpest vision and color vision (Foveal vision is 1.0 (20/20 or
6/6); and decreases as you move away)
• It is the center of visual axis
• located temporal to optic disc
• Fovea is a depression at the centre of the macula and shines during
Direct Ophthalmoscopy (Foveal reflex)
54
The Neurosensory Retina

55. Optic Nerve Head (Blind spot)
• is located nasal to the macula and measure 1.5 mm in diameter
• Its edge is located approximately 3.42 ± 0.34 mm from the foveal center
• Is an area of complete blindness in the visual field, as there are no
photoreceptors at this area
55
The Neurosensory Retina

56. Has two major layers:
• I- Outer layer
– Next to choroid, single layer of epithelial cell
– Contains rods and cones
– Avascular and gets its nutrition from the choroid by diffusion
• II- Inner Layer
– Consists of bipolar and ganglion cells as well as nerve fibers and
synapses
– Light passes through this to reach rod and cones
– Blood supply – by the central retinal vessels
56
The Neurosensory Retina

57.  Consists of two kinds of photoreceptors (Rods and Cones)
◦ These are antennae of the visual system that react with light and
light energy is transformed into a visual perception by the brain
◦ Rods - sensitive to dim lights that are found peripherally
◦ Cones - color & bright light sensitive cells that are found more
concentrated toward the center (Fovea)
◦ They produce electrical impulses when they are exposed to light
◦ Then the impulses passes across synapses to the bipolar and
ganglion cells and are modified in various ways
◦ The nerve fibers from the ganglion cells travel in the nerve fibers
layer on the surface of the retina to the optic disc and form the
optic nerve
57
The Neurosensory Retina

58. • The vitreous body is a clear, transparent, gel-like substance that fills
the eye between the lens and retina
• It is 16.5 mm in axial length with a volume of approximately 4 ml,
comprising approximately 2/3 to 4/5 of the volume of the globe.
• The refractive index of the vitreous is 1.334
• Its viscosity is 1.8 to 2 times that of water
• Function: - to act as intervening medium in the light pathway
between the lens and retina and also gives the shape of the eye
58
THE VITREOUS SPACE:

59. Visual pathway
• The visual path way connect the optic nerve with
the part of the brain concerned with vision, that is
with the occipital cortex.
• The optic nerve is the tract of the central nervous
system
• After damage the optic nerve will not regenerate
b/c of lack of Schwann cells around individual
fibers
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60. 60

61. Arterial blood supply
 The eye is supplied by anastomosing vessels from internal and
external carotid arteries.
 Retina - inner layer gets blood from central retinal artery, a
branch of ophthalmic artery and enters the eye with optic
nerve and divides on the optic disc into its branches.
 Uvea - is supplied by ciliary circulation, from ophthalmic
artery
 Eyelid gets its blood supply from facial and ophthalmic
arteries
 The EOMs are supplied by muscular branches from the
Cilliary branches of the Ophthalmic artery
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Blood supply of the eye

62. Venous Drainage
 Almost the entire blood from the anterior and posterior
Uvea drains through the vortex veins via superior and
inferior ophthalmic veins to the cavernous sinus
 Eyelid drains through facial vein into cavernous sinus
Lymphatic drainage
 There are no lymphatic vessels inside the globe.
 The lymphatic drainage of the medial eye lid is to the
submandibular lymph nodes and that of lateral one is
to the superficial preauricular lymph nodes and then to
deep cervical lymph nodes
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Blood supply of the eye

63. Motor Innervation
Oculomotor (CN III)- Innervates MR, SR, IR, & IO
Trochlear (CN IV)- Innervates SO
Abducens (CN VI)- Innervates LR
Facial nerve (CN VII) - innervates Orbicularis Oculi
Sensory Innervation
Ophthalmic branch of trigeminal nerve is the
sensory nerve of the globe & Adnexa and has three
branches -frontal, lacrimal, nasociliary
Optic nerve (CNII) - responsible for vision
63
Innervations of the eye

64. Autonomic Innervation
• Sympathetic nerve- supplies Muller's muscles and
dilator pupillae
• Parasympathetic comes via Oculomotor and
innervates the ciliary muscle and sphincter pupillae
64
Innervations of the eye

65. Thanks
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