Eyeball anatomy
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Transcript of Eyeball anatomy
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MOB TCD
Professor Emeritus Moira O’Brien
FRCPI, FFSEM, FFSEM (UK), FTCD
Trinity College
Dublin
Eyeball
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Eyeball
• Surrounded by Tenon’s fascia
• Attached to corneoscleral junction
• Dura on optic nerve• Check ligaments • Suspensory ligament of
Lockwood• Cone of muscles • Fat
MOB TCD
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• Consists of three coats• Outer layer• Sclera and cornea• Choroid• Retina
Eyeball MOB TCD
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Cornea
• Transparent• Avascular • Forms anterior 1/6 • Smaller sphere than sclera• Depression at
corneoscleral junction
MOB TCD
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Five Layers of Cornea
1. Corneal epithelium
2. Bowman’s or anterior limiting membrane
3. Substantia propria
4. Descement’s or posterior limiting membrane
5. Endothelium
MOB TCD
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• Posterior limiting membrane breaks up at the edges to form pectinate ligament of iris
• Spaces are called the spaces of the iridiocorneal angle (fontana)
Cornea MOB TCD
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Iridiocorneal Angle
• If the iridiocorneal angle is narrowed
• Reabsorption of aqueous humour into venous sinus of sclera is blocked
• Causing glaucoma• Blindness increased
intraocular pressure
MOB TCD
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• Cornea is avascular• Surface must be moist • Rheumatoid dry• Not wearing safety goggles• Scarring of cornea results
in blindness in that portion of the cornea
• Trachoma, new vessel formation in the cornea
• Transplants
Cornea MOB TCD
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Sclera
• Posterior 5/6 • Opaque • Insertion muscles• Vena vorticosae pierce at
equator• Optic nerve 2.3 mm medial to
axis, the lamina cribrosa• Central artery of retina • Long and short cilary vessels
and nerves
MOB TCD
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Suprachoroid Space
• Long ciliary nerves• Long posterior ciliary
arteries going to iris
MOB TCD
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Choroid
• Choroid proper• Ciliary body• Iris• Vascular layer in posterior
part• Equator of eyeball• Uveal tract or iridocyclitis
MOB TCD
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• Outer limiting membrane• Veins• Arteries• Capillaries• Inner limiting membrane of
bruch • Attached to pigmented
layer of retina
Choroid MOB TCD
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Ciliary Body
• Triangular• Apex posterior• Short base anterior• Deep surface thrown into
folds called the ciliary processes
• Ciliary body is vascular, pigmented
MOB TCD
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Ciliary Zonule
• Suspensory ligament of lens is attached to the cilary processes
• The portion of the suspensory ligament closest to the ciliary
• Processes is called the ciliary zonule
MOB TCD
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Ciliary Muscles
• Smooth muscle• Radial is attached to
scleral spur• Circular within anterior
part of radial muscle• Parasympathetic
oculomotor 3rd nerve• Relays in ciliary ganglion
MOB TCD
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Accommodation Reflex
• Contraction of ciliary muscles
• Ciliary processes pulled anteriorly
• Relaxes suspensory ligament of lens
• Elasticity of lens • It becomes more convex• Pupils constrict• Medial rectus contracts
MOB TCD
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Iris MOB TCD
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• Cone shaped diaphragm• Halfway along anterior of
base of choroid• Central aperture pupil• Vascular pigmented• Amount pigment colour• Blood vessels long
posterior, anterior cilary arteries; two circles
Iris MOB TCD
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• Circular sphincter pupillae • Oculomotor• Behind lies radial or dilator
pupillae• Sympathetic T1 develop
from ectoderm
Iris MOB TCD
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Aqueous Humour
• Aqueous humour is secreted by ciliary processes into posterior chamber
• Through the pupil into anterior chamber
• Spaces of fontana into venous sinus of sclera or canal of Schlemn
MOB TCD
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Posterior Chamber
• Bounded posteriorly by suspensory ligament of lens and lens
• Peripherally by ciliary processes
• Anteriorly by iris
MOB TCD
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Anterior Chamber
Anterior Chamber• Bounded posteriorly by iris and
pupil• Anteriorly by cornea• Peripherally by spaces of
fontana or iridio-corneal angle
MOB TCD
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Retina
• Nervous layer• Superficial to deep• Pigment cells• Rods and cones• Bipolar cells• Ganglion cells• Axons of the ganglion cells
form optic nerve
MOB TCD
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Rods
• Rods are found at peripheral portion of the retina
• 70 rods connected to one bipolar cell
• Peripheral vision• Visual purple sees back and
white
MOB TCD
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Cones
• Cones see colour • Photoreceptors• One cone to one bipolar cell• Found in fovea or macula
lutea• Directly behind axis• No nerve fibres or vessels
in front
MOB TCD
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Blood Supply of Retina
• Rods and cones supplied by capillaries of choroid by diffusion
• Bipolar and ganglion cells supplied by central artery of the retina
• Enters through optic disc, blind spot
MOB TCD
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Optic Disc MOB TCD
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Diabetic Hypertensive MOB TCD
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Detached Retina
• Outer layer of optic cup• Pigmented layer• Inner layer
rods and cones• Removed from their blood
supply
MOB TCD
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Refractive Media
• Cornea• Aqueous humour of anterior
and posterior chamber• Lens• Vitreous body
MOB TCD
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• Greatest refraction of light • Takes place at the surface
of the cornea
• Very little refraction after cornea
Refractive Media MOB TCD
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Lens
• Crystalline• Translucent• Avascular structure• Lies in hyloid fossa• Posterior surface is highly
convex
• Does not alter its shape
MOB TCD
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• Suspensory ligament is attached to periphery of the lens
• Cataract opaque lens• Nutrition from aqueous
humour
Lens MOB TCD
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• Supplied by hyloid • Artery during development• Hyloid artery regresses
remains as the hyloid canal• May persist, result a form of
blindness
Lens MOB TCD
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Vitreous Body
• Semiliquid• Translucent• Avascular gel• Enclosed in hyloid membrane• Opacities may develop in
elderly
MOB TCD
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Subconjunctival Haemorrhage MOB TCD
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