Anatomy Of Eye
Mohammad Ali A Sadiq, M.D
F.C.P.S (Pk) F.P.O.S (UK) F.A.A.P.O.S (Harvard)
Assistant Professor of Ophthalmology
King Edward Medical University
EYE
• Asymmetrical globe about an inch in diameter
(24mm)
• Cornea (Clear dome over the iris)
• Conjuctiva (thin layer of tissue covering the
front of eye)
• Sclera (White part)
• Iris (pigmented part)
• Pupil
EYE
• Lens – behind the iris and pupil
– Focus light on the back of the eye
• Vitrous – Gel filling the eye
• Retina – special light sensing cells
– Converts light into
electrical impulses
– Macula – small sensitive
Area in the center of retina
• Optic Nerve –carries
Impulses to the brain
Eyelid
• Thin fold of skin that covers and protects the
human eye.
• FUNCTIONS
– Regularly spread the tears and other secretions of
the eye surface.
– Responsible for corneal protection
– Responsbile for corneal nutrition
– Lashes provide additional protection
Eyelid
• LAYERS
– Skin
• Sweat glands
• Sebacoues glands
• Hair – eye lashes
– Subcuatneous tissue
– Orbicularis Oculi muscle
– Orbital septum
– Aponeurotic fat
– Levator palpebrae superioris
– Muller muscle
– Tarsal Plate
– Palperbral Conjuctiva
Lacrimal system
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LACRIMAL GLAND
– Secretes tears
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PUNCTI
– 0.3mm in diamter
– Sits on an elevated mound –
papilla lacrimalis
– Relatively avascular
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LACRIMAL CANALICULI
– Initial vertical segment – 2mm
– Horizontal segment -- 8mm
– Valve of Resonemuller
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LACRIMAL SAC
– Fundus – 3-5 mm
– Body – 10 mm
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NASOLACRIMAL DUCT
– 12mm Intraosseous portion
– 5 mm inferior membranous portion
– Valve of Hassner
CORNEA
• Transparent from part of the eye covering the
Iris, pupil and Anterior chamber
• Accounts for Approx 2/3rd of the refractive
power of the eye (43 Diopters)
• Completely avascular – recieves nutrients via
diffusion from the tear film and aqueous
humor
• Unmyelinated nerve endings sensitive to
CORNEA
• Diameter – 11.5 mm
• Thickness
– 0.5-0.6 mm in the center
– 0.6-0.8 mm in the periphery
• Layers
– Corneal Epithelium – non keratinized stratified sq cells
– Bowmans Layer – Anterior limiting membrane (Type 1 collagen fibrils)
– Corneal Stroma – regularly arranged collagen fibrils with keraotcytes
(Type 1 collagen fibrils)
– Descement’s membrane – Posterior limiting membrane (Type 1 and 4
collagen fibrils)
– Corneal Endothelium simple squamous or low cuboidal monolayer
AQUEOUS HUMOR
• Transparent, gelatinous fluid similar to plasma but low
in protein.
• FUNCTIONS:
– Maintains the IOP
– Provided nutrition to
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Cornea
Trabecular meshwork
Lens
Anterior Vitrous
– Presence of
Immunoglobulins
• Refractive Index
AQUEOUS HUMOR
• Secreted into the posterior chamber by the
ciliary body – pars plicata
• Drains out of the eye through the trabecular
meshwork
• Then into the schlem canal
– Directly into episcleral vein
– Indirectly through collector
channels
Conjuctiva
• Lines the inside of the eyelids and covers the
sclera
• Non keratinized stratified epithelium with
goblet cells
• FUNCTION
• Helps lubricate the eye by producing mucus
and lacrimal gland
• Contributes to immune surveillance of the eye
Conjuctiva
• Palpebral or Tarsal conjuctiva
– Lines the eyelid
• Bulbar or Ocular Conjuctiva
– Covers the eyeball over the sclera
– Tightly bound to underlying sclera by Tenon’s capsule
– Moves with eyeball movement
• Fornix Conjuctiva
– Junction between bulbar and Palpebral conjuctiva
– Loose and flexible
Sclera
• Forms the supporting wall of the eyeball
• Continuous with the clear cornea
• Thickest in the area surrounding the optic
nerve
• Thinnest at the insertion of the muscle
SCLERA
• Three Divisions
– Episclera
• Loose connective tissue immediately beneath the
conjuctiva
– Sclera Proper
• Dense white tissue that gives the area its colour
– Lamina Fusca
• Inner most zone made up of elastic fibres
IRIS
• Thin, circular structure in the eye responsible for
controlling the diameter and size of the pupil
• TWO LAYERS
– Storma
Front pigmented fibrovascular layer
• Connects to
– Spincter muscle – sphincter pupillae
– Dilator muscle – Dilator pupillae
– Pigmented Epithelial cells
• Two cell thick
IRIS
• Outer edge of the iris is attached to
– Sclera
– Anterior ciliary body
• IRIS AND CILIARY BODY TOGETHER ARE KNOWN AS
ANTERIOR UVEA
• PORTIONS OF THE IRIS
– Pupillary zone – inner region whose edge forms the boundary of
the pupil
– Cilliary Zone – rest if the iris that extends to its origin at the
ciliary body
– Collarette – region when the sphincter and dilator muscle
overlap
LENS
• Transparent bi-convex structure
• Helps in refracting light (18 diopters) – one third of the
eyes total power
• Ability to change shape – Accomodation
• Suspended in place by the suspensory ligaments
• 10 mm in diameter.
• Axial length of 4mm
LENS
• COMPONENTS OF LENS
– LENS CAPSULE
• Smooth transparent basement membrane
• Elastic membrane composed of collagen (type 4)
• Varies from 2 to 28 micrometers – thickest at the equator
– LENS EPITHELIUM
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Anterior portion of the lens between the capsule and lens fibers
Simple cuboidal epithelium
Regulates most of the homostatic functions of the lens
Progenitor for new lens fibers
– LENS FIBERS
• Bulk of the lens
• Long, thin , transparent cells, firmly packed.
• Diameters typically 4-7 microns and length upto 12 mm
VITROUS
• Clear gel filling the space between retina and the lens
• Remains unchanged throughout life
• Produced by cells in the non pigmented portion of the ciliary body
• 98-99% of the body is water
• Strongly connected to the optic disc and the orra serrata
• Loosely connected to the macula and blood vessels
• As human ages, it liquefies and often collapses
CHOROID
• Thin vascular layer between the sclera and the retina
• Supplies blood to the retina and conducts arteries and
nerves to other structures in the eye
• FOUR LAYERS
– Haller’s layer – outermost layer consisting of large blood
vessels
– Sattler’s layer – layer of medium diameter blood vessles
– Choriocapillaris – layer of capillaries
– Bruch’s membrane – Inner most layer of the choroid
RETINA
• L atin word “rete” meaning net
• Inner most, light sensitive layer of the eye
• Light striking the retina initiates a cascade of chemical and electrical
events that trigger a nerve impulse
• PHOTORECEPTOR CELLS
– RODS
• Dim light
• Black and white vision
– CONES
• Suuport day time vision
• Colour perception
– Ganglion cells
• Reflexive response to bright daylight
RETINA
• LAYERS OF RETINA
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Inner Limiting membrane
Nerve Fiber layer – axons of ganglion cell nuclei
Ganglion cell layer
Inner Plexiform layer – Contains synapses between bipolar axons and
denrites of ganglion and amacrine cells
Inner Nuclear Layer – contains the nuclei of amacrine cells
Outer pelxiform layer – projections of rods and cones
Outer nuclear layer – cell bodies of rods and cones
External limiting membrane layer – layer that separates the inner
segment portions of the photoreceptors from their cell nucleus
Layer of rods and cones
Retinal Pigment Epithelium - single layer of cuboidal cells. This is
closest to the choroid.
EXTRA-OCULAR MUSCLES
• 6 Extra-ocular muscles
• 4 Rectus muscles
• 2 Oblique muscles
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M.R – 5.5mm from limbus
I.R ``– 6.5 mm
L.R -- 6.9 mm
S.R -- 7.7mm
OPTIC NERVE
• Extension of the brain
• Energy transmission from retina to the brain
• Subject to underdevelopment, damage.
Inflammation
• Over 1 million nerve fibers
• Once it is severed, it cannot be reconnected
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• THANK YOU