EYE Dr Manodeep Chakraborty Structure Outer fibrous layer

EYE Dr. Manodeep Chakraborty

� Structure Ø Outer fibrous layer ü Sclera ü Cornea Ø Middle vascular layer ü Chroid ü Ciliary body ü Iris Ø Inner nervous layer ü Retina Ø Lens, Aqueous layer & Vitreous body are present inside the eye ball

� Sclera & Cornea � The sclera forms the outer most layer of the posterior & lateral aspects of the eye ball (white part of the eye) & is continuous anteriorly with the transparent cornea

� Choroid � The choroid lines the posterior 5/6 th of inner surface of the sclera � Ciliary body is the anterior continuation of the choroid consisting of ciliary muscle (smooth muscle fibres) & secretory epithelial cells

� Iris is the visible coloured part of the eye & extends from ciliary body, lying behind the cornea & infront of the lens � Lens is a highly elastic circular biconvex body having immediately behind the pupil

� Retina is the innermost delicate layer of the wall of eye � Blood supply ü Artery ü Venous

� Interior structure of eye ü Vitreous body It is a soft colour less transparent, jelly like substance composed of 99% H 2 O, salts, mucoprotein

ü Optic nerves ü Optic chiasma ü Optic tracts

� Physiology of vision � Retinal image formation ü Refraction of light rays ü Accommodation of the lens ü Change in the size of the pupil ü Convergence of eyes � Stimulation or activation of photo receptors � Dark adaptation � Dilation of pupil � Light adaptation

� Accessory organs of eye ü Eye lids ü Eye brows ü Conjunctiva ü Eye lid margin ü Lacrimal apparatus ü Eye lashes

� Conjunctiva is a fine transparent membrane that lines the eyelids & the front of the eye ball � Lacrimal apparatus ü 1 lacrimal gland & its ducts ü 2 lacrimal canaliculi ü 1 lacrimal sac ü 1 nasolacrimal duct � Functions Ø Washing away irritating materials e. g. dust, grit Ø The bacterial enzyme lysozyme prevents microbial infection Ø Its oiliness delays evaporation and prevents drying of the conjunctiva