Anatomy of Eye.pptx

It describe the anatomy of eye in detail according to the BD chaurasia textbook.
It includes the parts of eye, internal structures, blood and nerve supply.

1. Eyeball

2. Introduction Sense of sight perceived through retina of the eyeball is one of the five speacial senses. The eyeball is the organ of sight. It is almost spherical and has a diameter of a out 2.5 cm. Eyeball is made up of three concentric coats. The outer fibrous coat comprises the sclera and the cornea. The middle or vascular coat also called the uveal tract consists of the choroid , the ciliary body and the iris. The inner nervous coat is the retina. Light entering the eyeball passess through several refracting media.

3. Outer coat Sclera Cornea

4. Sclera Opaque and forms the posterior five sixth of the eyeballs. Composed of dense fibrous tissue which is firm and maintains the shape of the eyeball. Thickest behind near the entrance of the optic nerve Thinneat about 6mm behind sclerocornal junction Weakest at the entrance of optic nerve

5. Lamina cribrosa The sclera shows numerous perforations for passage of fibres of the optic nerve near it’s entrance. Because of its sieve like appearance , this region is called the lamina cribrosa.

6. Outer surface of sclera White and smooth Covered with Tenon’s capsule. Anterior part covered with conjunctiva .

7. Inner surface Brown and grooved for the ciliary nerves and vessels. Sperated from the choroid by the perichoroidal space containing a delicate tissue called suprachoroidal lamina.

8. Canal of Schlemm Sclera is continous anteriroly with the cornea at the sclerocornal junction or limbus. The deep part of the limbus contains a circular canal known as the sinus venosus sclerae or the cabal of schlemm The aqueous humor drains into the anteriro scleral or ciliary veins through this sinus.

9. Dural sheath of optic nerve The sclera is fused posteriorly with Dural sheath of the optic nerve. It provides insertion to the extrinsic muscles of the eyeball: 1) the recti in front 2) the oblique muscle behind

10. Peircings of the sclera Optic nerve Ciliary nerves Anterior ciliary arteries
Four venae vorticosae

11. Episclera The sclera is almost avascular. However, the loose connective tissue between the conjunctiva and sclera called as the elisclera is vascular.

12. Cornea Transparent Replaces sclera over anteriro one sixth of the eyeball Junction with. Sclera is called sclerocornal junction More convex than sclera Seperated from the iris by a space called the anterior chamber of the eye. Cornea is avascular and is nourished by lymph which is circulated in numerous corneal spaces and by lacrimal fluid.

13. It is supplied by branches of the opthalmic nerve and short ciliary nerves. Pain is the only sensation aroused from the cornea.

14. Histology/ Microanatomy Structurally, the cornea consists of these layers, from before backwards: 1. Corneal epithelium (stratified squamous non keratinized type) 2. Bowman’s membrane 3. Substantia propria 4. Descemet’s membrane 5. Simple squamous mesothelium

15. Middle Coat 1) Choroid 2) Ciliary body 3) Iris

16. Choroid Choroid is a thin pigmented layer which separates the posterior part of the sclera from the retina. Anteriorly- ora serata Posteriorly perforated by optic nerve

17. Outer surface Separated from the sclera by the Suprachoroidal lamina which is traversed by ciliary vessels and nerves . It’s attachment to the sclera is loose so that it can easily be stripped

18. Inner surface The inner surface is firmly United to the retina: Suprachoroid lamina Vascular lamina The choriocapillary lamina The inner basal lamina prembrane of bruch

19. Ciliary body It is the thickened part of the uveal tract t just posterior to the corneal limbus Continous anteriorly with iris Posteriorly with choroid It suspends the lens and helps it in accomodation for near vision

20. Ciliary body Triangular in cross section Thick in front and thin behind The scleral surface of this body contains the ciliary muscles Posterior part of viterous humor is smooth and black ( pars plana) Anteriro part – ridged anteriroly ( pars plicata) to form about 70 ciliary processes. The central ends of the processes are free and rounded.

21. Ciliary zonule Thickened viterous membrane Fitted to the posterior surface of ciliary process

22. Ciliary muscle Ring of unstriped muscle which are longitudinal or meridonial, radial and circular. Longitudinal /meridonial fibres arise from a projection of sclera or scleral spur near the limbus. They radiate backwards to the Suprachoroidal lamina. The radial fibres are obliquely placed and get continous with the circular fibres.

23. Circular fibres Lie in the anterior part of the ciliary body and are nearest to the lens Contraction of all the parts relaxes the suspensory ligament so that the lens becomes more convex. All parts of the muscle are supplied by parasympathetic nerves.

24. Iris Anterior part of uveal tract Circular curtain with an opening in The centre called the pupil. By adjusting the size of the pupil it controls the amount of light entering the eye.

25. It is placed vertically between the cornea and the lens, thua divides the anterior and posterior chambers both containing aqueous humor. It’s peripheral margin is attached to the middle of the anterior surface of the ciliary body and is anterior surface of the ciliary body. Central margin is free and forms the boundary of the pupil.

26. The anterior surface of the iris is covered by a single layer of mesothelium Posterior surface by a double layer of deeply pigmented cells The main bulk of the iris is formed by stroma made up of blood vessels and loose connective tissue in which there are pigment cells

27. Arterial circle The long posterior and anterior ciliary arteries join to form the major arterial circle . Form this circle the vessels converge towards the free margin to form the minor arterial circle of iris.

28. The colour of iris is determined by the number of pigment cells in its connective tissue. If the pigment cells are absent , the iris is blue in colour The iris contains a well developed ring of muscle called the sphincter pupillae which lies near the margin of the pupil.

29. Dilator pupillae An ill define sheet of radial muscle fibres placed near the posterior surface of the iris. Supplied by sympathetic nerves.

30. Inner coat (Retina) Thin, delicate inner layer Continous posteriorly with optic nerve Outwr surface attached to choroid, inner surface to hyaloid membrane of viterous.

31. Optic disc Opposite the entrance of the optic nerve , there is circular area known as the optic disc. It is 1.5 mm in diameter

32. Parts of retina Optic Ciliary Iridial

33. Ora serrata The anterior margin of optic part of the retina forms a Wavy line called the ora serrata.

34. Physiological cup Contains no rods or comes Insensitive to light Also called physiological blind spot for the same reasons.

35. Macula lutea At the posterior pole of eye 3 mm lateral to the optic disc there is another depression of similar size called macula lutea. It is avascular ( no blood vessels) Yellow in colour

36. Fovea centralis The centre of macula is further depressed to form the fovea centralis. This is the thinnest part of retina. It contains cones only and is site of maximum acuity of vision.

37. Rods Light receptors of the eye Rods contain a pigment called visual purple. They respond to dim light The periphery of retina contains only rods, but the fovea has none at all.

38. Cones Responds only to bright light Sensitive to colour Fovea centralis have only cones Their number diminishes towards the periphery of the retina.

39. 10 layers of retina Outer pigmented layer Layer of rods and cones External limiting membrane Outer nuclear layer Outer plexiform layer Inner nuclear layer Inner plexiform layer Ganglion cell layer Nerve fibre layer Internal limiting membrane

40. Arterial and venous supply Arterial supply- central artery Cones and rods- supplies by diffusion from the capillaries of the choroid. The retinal veins run with arteries.

41. Aqueous humor Clear fluid which fills the space between the cornea in front and lens behind the anterior segment. The aqueous humor is secreted into the posterior chamber from capillaries in the cilairay processes. It passes into the anteriro chamber Through pupil Fromnanteriro chamber, it is drained into anteriorr ciliary veins through the spaces of the irido corneal angle and the canal of Schlemm.

42. Intraocular pressure is due chiefly to the aqueous humour which maintains the constancy of the optical dimension of the eyeball. The aqueous is rich in ascorbic acid, glucose and amino acids and nourishes the avascular tissues of the cornea and lens.

43. Lens Transparent biconvex structure Lies between the anterior and posterior chamber Circular in outline Diameter of 1 cm Central points of anterior and posterior chambers is called anterior and posterior poles Lines connecting the poles constitute axis of lens. Marginal circumference of the lens is termed equator It contributes about 15 dioptres to the total 58 dioptric power of the eye.

44. Dioptres They determine the optical power of the eye and thus defines the Vergence of the optical beams helping in forming a clear picture at particular distance

45. The posterior surface of lens is more convex than anteriro. The anterior surface is flat because of the suspensory ligament. When the ligament is relaxed by contraction of the Ciliary muscle , the anteriro surface becomes more convex due to elasticity of the lens substance. The lens is enclosed in a transparent, structureless elastic capsule which is thickest anteriroly.

46. Histology of lens Covered by capsular epithelium At the centre the epithelium is made up of cubical cells. At periphery it is made up of cells that elongate to form the fibres. The fibres are concentrically arranged to form the lens substance. The centre ( nucleus) of the lens is firm. The periphery is soft and is made up of more recently formed fibres

47. Viterous body Colourless jelly like transparent mass which fills the posterior 4/5 th of the eyeball. Enclosed in a delicate hyaloid membrane. Posteriorly attached to optic nerve Anteriroly attached to ora seratta In between it is free and is attached to the retina

48. The end