Eye

Maj Dr Rishi Pokhrel

MBBS, MD

Dept of Anatomy, NAIHS

Introduction

• Peripheral organ of vision

• Present in anterior part of orbit

• 1 inch in diameter

• Orbital fascia and bulbar fascia

Orbital fascia and bulbar fascia

.

FASCIA BULBI (Tenon's capsule)

• It is a thin membrane which envelops eyeball from optic nerve to ciliary region;

• allows eyeball to move freely

• smooth inner surface pierced by vessels and nerves

• fuses with sheath of optic nerve and sclera

• lower part of membrane thickens into suspensory ligament (checks ligaments) which attaches to zygomatic arch and lacrimal bones.

Structure

Structure• Outer fibrous coat

is composed of– Sclera

– Cornea

• Middle vascular coat comprises– Choroid

– Ciliary body

– Iris

• Inner nervous coat consists of– Retina

CORNEA• half inch wide convex and

transparent layer.

• 5 layered

• Anterior chamber separates it from iris.

• avascular, nourished by lymph and aqueous humor

• rich nerve supply.

• Its junction with sclera is limbus.

SCLERA

• This visible white part of the eye is covered with conjunctiva.

• made up of dense fibrous tissue.

• It provides attachments to tendons of recti and obliqui.

• It is pierces by numerous nerves and vessels.

CHOROID

• It lines sclera and

separates it from

retina.

• consists of pigmented

tissue containing nerve

plexuses, network of

capillaries, arteries and

superficially veins.

CILIARY BODY

• connects choroid with iris.

• made up of ciliary processes (internally) and ciliary muscle (externally).

CILIARY MUSCLE

• muscular ring placed deep to anterior part of sclera.

• made up of radial and circular fibres.

• brought into action during accommodation e.g. it slackens suspensory ligament of lens thus making it move convex as is required for near vision.

IRIS• placed b/w lens and

cornea

• circular, colored and contractile curtain.

• central aperture – pupil

• made up of smooth muscle called sphincter pupillae and dilator pupillae.

• Decrees and increase the size of pupil - aperture

RETINA• Light sensitive layer

• 10 layers

• Cells - Rods and cones

• two components.– Pigmented layer (external layer) is attached to

choroid and continues over ciliary body to iris.

– Retina proper (internal layer) is in contact with vitreous. Ora serrata divides it into posterior optic part and anterior ciliary part.

• Ora serrata - wavy border behind the ciliary body.

RETINA

• Macula lutea- at posterior pole of eyeball on retinal is a small yellowish spot.

– It presents fovea centralis - cones

ROD CONE

• Optic disc – point where optic nerve

fibers converge to leave eyeball.

– 1 mm below and 3 mm medial to posterior pole.

– Its circumference is raised while its centre is depressed called optic cup.

– The disc is the blind spot of eye as it lacks nervous elements.

LENS

• transparent and circular, b/w vitreous and iris

• Biconvex, 10 mm in diameter and 4 mm thick.

• Ciliary muscle contraction -> slackening of suspensory ligament -> thickening of lens -> near vision

• ANTERIOR CHAMBER

• It is the space between cornea anteriorly & iris and central part of lens posteriorly

• POSTERIOR CHAMBER

• It is behind iris and suspensory ligament and adjoining part of lens posteriorly. The two chambers communicate through pupil; filled with a clear fluid called aqueous humor.

• VITREOUS HUMOUR (Vitreous body)

• transparent and jelly like substance that fills posterior 4/5 of eyeball.

• enclosed in a transparent membrane (hyaloid membrane)

CLINICAL ANATOMYCataract

• progressive condition of lens characterized by loss of transparency.

• a gray-white opacity in the lens.

• Congenital cataracts are usually hereditary but may be caused by viral infection during first trimester of gestation.

• Senile cataracts are uncomplicated cataracts of old age. Vision is lost if cataracts are not treated.

Retinal detachment• separation of retina

from choroid.

• The retina does not contain sensory nerves; thus condition is painless.

• D begins at the thin peripheral edge of retina and extends gradually beneath thicker central areas.

• is not checked it results in blindness.

Corneal grafting (keratoplasty)

• This surgical procedure of transplantation of cornea is performed to improve vision in corneal scarring, distortion or perforation.

Glaucoma

• elevated intraocular pressure because of obstruction of outflow of aqueous humour. Glaucoma may be:

– Acute (narrow angle)

– Chronic (wide angle) glaucoma

Corneal reflex

• protective mechanism for eye where eyelids close when cornea is touched.

• mediated by ophthalmic division of 5th cranial nerve (sensory) and 7th cranial nerve (motor).

• This reflex may be used as a test of integrity of those nerves.

queries

Ant Epithelium

Bowman’s membrane

Substantia propria (Stroma)

Descemet’s membrane

Post Epithelium / Endothelium

Layers of Cornea

Uvea

• Vascular layer

• 3 Parts

– Choroid

– Ciliary body

– Iris

Retina

Introduction

• Neural Photoreceptor layer

• Development

– Optic vesicle - cup

– Outer layer- Pigment

– Inner layer- Neural

– Detachment

ROD CONE

Layers• Ten layers– Outside in

– Retinal Pigment epithelium

– Outer segment & Inner segment - Photoreceptors

– External Limiting membrane

– Outer Nuclear

– Outer Plexiform

– Inner Nuclear

– Inner Plexiform

– Ganglion cell

– Optic nerve fibre

– Internal Limiting membrane

• Mnemonic: Please Reply MY New Post, Never Pray God

For Money

– NB- Outside in- ? Dir light/Impulse

Layers Of The Retina

10

9

8

7

6

5

4

3

2

1

1. Retina contains photosensitive cells.

The outer limit of the retina is the Pigmented Epithelium (PEp)

1. Choroid (Ch) is a highly vascular layer containing melanocytes and

separated from the retina by the epithelial basement membrane

(Bruch’s membrane)

3. Sclera (S) consists of dense fibroelastic connective tissue

3 Coats Of The Eye

s