MOB TCD

Professor Emeritus Moira O’Brien

FRCPI, FFSEM, FFSEM (UK), FTCD

Trinity College

Dublin

Eyeball

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

• Consists of three coats• Outer layer• Sclera and cornea• Choroid• Retina

Eyeball MOB TCD

Cornea

• Transparent• Avascular • Forms anterior 1/6 • Smaller sphere than sclera• Depression at

corneoscleral junction

MOB TCD

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

• 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

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

• 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

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

Suprachoroid Space

• Long ciliary nerves• Long posterior ciliary

arteries going to iris

MOB TCD

Choroid

• Choroid proper• Ciliary body• Iris• Vascular layer in posterior

part• Equator of eyeball• Uveal tract or iridocyclitis

MOB TCD

• Outer limiting membrane• Veins• Arteries• Capillaries• Inner limiting membrane of

bruch • Attached to pigmented

layer of retina

Choroid MOB TCD

Ciliary Body

• Triangular• Apex posterior• Short base anterior• Deep surface thrown into

folds called the ciliary processes

• Ciliary body is vascular, pigmented

MOB TCD

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

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

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

Iris MOB TCD

• 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

• Circular sphincter pupillae • Oculomotor• Behind lies radial or dilator

pupillae• Sympathetic T1 develop

from ectoderm

Iris MOB TCD

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

Posterior Chamber

• Bounded posteriorly by suspensory ligament of lens and lens

• Peripherally by ciliary processes

• Anteriorly by iris

MOB TCD

Anterior Chamber

Anterior Chamber• Bounded posteriorly by iris and

pupil• Anteriorly by cornea• Peripherally by spaces of

fontana or iridio-corneal angle

MOB TCD

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

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

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

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

Optic Disc MOB TCD

Diabetic Hypertensive MOB TCD

Detached Retina

• Outer layer of optic cup• Pigmented layer• Inner layer

rods and cones• Removed from their blood

supply

MOB TCD

Refractive Media

• Cornea• Aqueous humour of anterior

and posterior chamber• Lens• Vitreous body

MOB TCD

• Greatest refraction of light • Takes place at the surface

of the cornea

• Very little refraction after cornea

Refractive Media MOB TCD

Lens

• Crystalline• Translucent• Avascular structure• Lies in hyloid fossa• Posterior surface is highly

convex

• Does not alter its shape

MOB TCD

• Suspensory ligament is attached to periphery of the lens

• Cataract opaque lens• Nutrition from aqueous

humour

Lens MOB TCD

• Supplied by hyloid • Artery during development• Hyloid artery regresses

remains as the hyloid canal• May persist, result a form of

blindness

Lens MOB TCD

Vitreous Body

• Semiliquid• Translucent• Avascular gel• Enclosed in hyloid membrane• Opacities may develop in

elderly

MOB TCD

Subconjunctival Haemorrhage MOB TCD

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