Gross Anotomy and Histology of Eyeball - Dr. Kapil Amgain

EYEBALL

Chair Person: Dr. R.D. VirupaxiPresenter: Dr. Kapil Amgain

Scheme of Presentation

• Introduction• Structure• Blood supply• Nerve supply• Applied Anatomy

Introduction• The organ of

sight• Occupies the

ant.1/3 of the orbital cavity

• Embedded in fat, separated by a membranous sac, the fascia bulbi.

• Eyeball closely resembles the Camera

• Two poles• Two axes• Eqator: an

imaginary line arround the eye ball equidistance from the two poles.

• Meridian: an imaginary plane from pole to pole and cutting the equator at the right angle.

Concentric coats/tunics of eyeball

• Outer fibrous coat: Sclera and Cornea• Middle vascular coat: Choroid, Ciliary Body

and Iris• Inner nervous coat: Retina

Structure piercing the sclera

• Optic nerve• Post.ciliary

vessel and nerve• Venae

vorticosae• Ant ciliary artey

Cornea

• Structure

Histology of the cornea

Choroid

• A thin pigmented layer which separates the post. part of the sclera from the retina.

Histology of the choroid

Ciliary body• A thickened

part of uveal tract lying just post.to the corneal limbus.

• Pars plana (ciliary ring)

• Pars plicata

Iris

• It resembles the diaphrgm of camera

Inner coat or Retina

• It is the thin, delicate inner layer of the eyeball• Continuous posteriorly with the optic nerve

Histology of the retina

Aqueous humour

Composition• Amino acids

transported by cilliary muscles.

• 98% water• Electrolytes• Ascorbic acid• Glutathione

Vitreous humour/body• The vitreous is the

transparent, colourless, gelatinous mass that fills the space between the lens of the eye and the retina lining the back of the eye.

• It is produced by cells in the non-pigmented portion of the ciliary body deriven from embryonic mesenchyme cells which then degenerate after birth.

Vitreous Body

• Its composition is similar to the cornea, but contains very few cells (mostly phagocytes which remove unwanted cellular debris in the visual field, as well as the hyalocytes of the surface of the vitreous, which

reprocess the hyaluronic acid), No blood vessels.

• Water = 98-99% of its volume (75% in the cornea) • Salts, sugars, vitrosin (a type of collagen), • a network of collagen type II fibres• Glycosaminoglycan • Hyaluronic acid and many proteins in micro amounts. • The vitreous body has a viscosity two to four times

that of pure water, giving it a gelatinous consistency. • It also has a refractive index of 1.336

Lens

• The crystalline lens is a transparent, biconvex structure in the eye that, along with the cornea, helps to refract light to be focused on the retina.

• The lens, by changing shape, functions to change the focal distance of the eye so that it can focus on objects at various distances, thus allowing a sharp real image of the object of interest to be formed on the retina

Histology of the lens

Movement of eyeball

• E:• D:• MR:• LR:• In:• Ex:

Action of extraoccular Muscle

Development of eyeball

Light Reflex

• Shining light into one eye causes constriction of iris muscles on both sides

Accommodation Reflex• Directing eyes

from a distant object to a near object causes constriction of iris muscles on both sides.

Consensual light reflex

Blood Supply of eyeball

Blood supply of eyeball

• Ophthamic artery

Nerve supply

• Sclera: • Cornea:ophthalmic nerve through long

ciliary nerve which form 4 plexus as they reach the cornea (anular, proprial, subepithelial and intraepithelial

• Choroid:• Ciliary muscle: parasympathetic nerve• Iris:

Applied Anatomy

• Conjunctivitis• Glaucoma• Corneal opacities• Corneal grafting• Jaundice can be visualized on the bulbar

conjuctive• Myopia• Hypermetropia• Presbyopia/Astigmatism

Conjunctivitis

Closed angle glaucoma

Open-Angle Glaucoma• Primary Open-

Angle Glaucoma:

The drainage angle is open within the eye, but for unknown reasons, does not allow fluid to drain.

Glaucoma: Open vs Closed angle

Papiloedema & Papillitis

• Cupping of optic disc

• Atrophy of optic nerve due to chronic pressure

Episcleritis

Myopia vs Hypermetropia

Astigmatism