ANATOMY OF THE EYE

Dr.T.Kurinchi MS

GROSS ANATOMY OF THE EYEBALL

INTRODUCTION

• Eyeball is a cystic structure, referred as a globe.

• It is not a sphere but an ablate spheroid.• It has two pole anterior and posterior pole• Between these two poles is the equator of the

eye ball.• Antero-posterior diameter of the eye is 24mm

Layers of the Eyeball

It has three concentric layers.• Outer fibrous layer –cornea, sclera, limbus.• Middle vascular layer [uveal tract] – iris,ciliary

body,and choroid• Inner neural layer -retina

SEGMENTSANTERIOR SEGMENT:• Consist of cornea to the crystaline lens• It as two chambers.• Anterior chamber- from endothelium of cornea to

endothelium of iris.• ACD is 2.5mm and contains aqueous humour• Posterior chamber- from iris epithelium [posterior iris] to

anterior surface of the lens.

POSTERIOR SEGMENT : posterior to lens which includes vitreous, choroid, retina, and optic disc.

TEAR FILM

• It has three layers.• Outer lipid layer, middle aqueous layer, inner

mucin layer.• It forms the coat over the cornea and

conjuntiva and protects it.

CONJUNCTIVA

• It is derived from surface ectoderm.• It is a translucent mucous membrane which

lines the anterior aspect of the eye ball and posterior surface of the eyelid.

• Can be divided into three parts:– Palpabral conjunctiva– Bulbar conjunctiva– Conjunctival fornix.

CORNEA• It is transparent, avascular, elliptical in shape , being 12mm

horizontally and 11mm vertically innervated by ophthalmic division of trigeminal nerve.

• Its dioptric power is 44D, Refractory index – 1.34.

It has five layers • Corneal epithelium, derived from surface ectoderm• Bowman’s membrane• Stroma }• Descemet’s membrane } Mesoderm• Endothelium }

SCLERA

• Dense opaque tough fibrous envelope and covers the posterior 5/6th of the eyeball.

• It has three layersEpiscleraSclera properLamina fusca

• Blood supply – episcleral and choroidal vessels• Nerve supply – Short ciliary nerve posteriorly

and long ciliary nerve anteriorly.

LIMBUS

• Junction between cornea and sclera.• 1 – 2mm in width.

ANGLE OF ANTERIOR CHAMBER

• It is anteriorly bounded by corneo-sclera, posteriorly by root of iris and ciliary body.

• It is aqueous drainage pathway.

UVEA• Anterior: Iris, a free circular diaphragm with central opening called Pupil.• Iris separates anterior chamber from the posterior.• Derived from mesoderm.• Colour – brown , Pattern – Collarette.• It has to muscles viz • Sphincter pupillae – running around pupillary margin, causes pupillary

constriction. • Nerve: Sensory – Nasociliary N, branch of 5th nerve• Motor: Occulomotor nerve.• Dilator pupillae arranged radially near root of the iris – causes pupillary

dilatation.• Nerve: cervical sympathetic chain.

CILIARY BODY:• Middle portion of uvea composed of ciliary muscles.• It has two regions viz • Pars plicata – about 70 plication, has ciliary process

responsible for production of aqueous• Pars plana – posterior smooth part, safe and

avascular zone for pars plana lensectomy and vitrectomy procedures.

CHOROID

• It is posterior part of uvea. • This is a vascular sheet which separates sclera

from retina.

CRYSTALLINE LENS

• It is transparent biconvex structure derived from surface ectoderm.

• Dioptric power : 16 – 20mm.• It is about 9mm in diameter, 4mm in thickness

suspended by suspensory ligament called zonules. Structure of Lens:• Anterior lens capsule• Anterior lens epithelium• Lens substance – consists of elongated lens fibres

VITREOUS CAVITY

• Contain vitreous humour which transparent gel like structure.

• Derived from mesoderm.• It is composed of network of collagen fibres

and hyaluronic acid.

RETINA• Is membranous light sensitive layer of the eyeball.• It is transparent in life and whitish after death.• It has ten layers

1. RPE2. Layers of rods and cones3. External limiting membrane4. Outer nuclear layer5. Outer plexiform layer6. Inner nuclear layer7. Inner plexiform layer8. Ganglion cell layer9. Nerve fibre layer10. Internal limiting membrane.

NORMAL FUNDUS PHOTOGRAPH

• Central retina – 4.5mm in diameter. It extends from fovea centralis nasally to the optic disc.

• The central part is called Macula lutea.

VISUAL PATHWAY

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