ANATOMY OF EYE.pptx

Anatomy of eye
Veterinary

1. SUBMITTED BY Meenu P M MVSc Scholar Department of Veterinary Surgery & Radiology, PGIVAS, Akola ANATOMY OF EYE

2. Definition Ophthalmology- The science dealing with the anatomy, functions, pathology & treatment of the eye Optometry- Optometry is a specialized health care profession that involves examining the eyes and related structures for defects or abnormalities Orthoptics- Orthoptics is an allied health profession pertaining to the study of eye movements and binocular vision.

3. Eyeball & its surrounding Eyeball is situated within the bony cavity- Orbit Within the orbit- surrounded by muscles & a thick padding of retrobulbar fat Anteriorly it is protected by eyelids Each eyeball is maintained in position by the action of extra ocular muscles Anterior segment (between cornea & lens)- Cornea, iris, pupil & lens Posterior segment (between lens and retina)- vitreous body & retina

4. Orbit Bony cavity which accommodates the eyeball Orbital cavity formed by- frontal, lacrimal , malar & sphenoid bones Orbital rim formed by- frontal, lacrimal & malar bones

5. Orbit (continue) Closed orbit (complete orbital rim)- cattle, buffalo, sheep, goat, horse, camel & man Open orbit (incomplete orbital rim)- cat, dog, pig, elephant & birds Skull of horse Skull of dog

6. Eyelids Mobile folds of skin protecting the eyeball anteriorly Upper eyelid is more mobile Upper & lower eyelids joins at lateral & medial canthus Slit between eyelids- Palpebral fissure Inner surface- Palpebral conjunctiva Border of eyelids contains the eye lashes (cilia)

7. Eyelids (continue) Glands of the eyelids Tarsal gland- Sebaceous gland Zeis gland- Modified sebaceous glands Moll gland- Sweat glands Function of eyelids Protects intra orbital structures Reforms the tear film Pumps tears into drainage system In newborns- closed eyelids protect the eye from drying

8. Third eyelid Synonym- Nictitating membrane/ Membrana nictitans Thin T-shaped cartilage covered by conjunctiva (comma shaped-camels) Located at medial canthus of the eye Deep part- embedded in retrobulbar fat Free end- partially moves over anterio - medial aspect of the eye Nictitating gland (Harderian/Harder’s gland) Situated on inner surface of the third eyelid close to its border Resembles lacrimal gland

9.  Transverse section of the third eyelid.  A,  Gland of the third eyelid;  B,  cartilage of the third eyelid.

10. Conjunctiva Mucous membrane which covers the front portion of sclera & cornea & is reflected to the inner surface of the eyelids The conjunctiva has two parts Palpebral conjunctiva- L ines eyelid- thick, opaque & red Bulbar conjunctiva- Remains attached to the eyeball- thin & transparent

11. Conjunctiva (continue) Fornix- Junction of palpebral conjunctiva & bulbar conjunctiva Cul-de-sac- Fold formed by junction of the palpebral conjunctiva & bulbar conjunctiva   Conjunctiva is composed of a non-keratinized, stratified squamous epithelium and substantia propria. It contains goblet cells in its outer epithelium, which produce the mucoid portion of the tear film, lymphoid tissue in its middle layer, and connective tissue, blood vessels and nerves in the deepest layer. 

12. Lacrimal apparatus Lacrimal gland- Secretes tears Location- Beneath conjunctiva in depression between supraorbital process & dorsolateral surface of eyeball Lacrimal apparatus- lacrimal gland, caruncula lacrimalis, puncta lacrimalis, lacrimal canal, lacrimal sac & nasolacrimal duct Additional accessory lacrimal glands are present in the conjunctiva

13. Lacrimal apparatus

14. Lacrimal gland (continue) Function of tears: Provide nourishment to the cornea Lysozymes & leukocytes provide antibacterial activity Wash away waste products & foreign bodies Provide lubrication for the movement of the eyelids over the cornea & bulbar conjunctiva

15. Muscles of eyeball There are 7 muscles- 5 straight & 2 oblique Superior rectus muscle/Dorsal rectus muscle Inferior rectus muscle/Ventral rectus muscle Lateral rectus muscle/External rectus muscle Medial rectus muscle/Internal rectus muscle Posterior rectus muscle/Retractor oculi muscle Superior oblique muscle Inferior oblique muscle

16. Muscles of eyeball (continue) All the straight muscles originate around the optic foramen & insert to the sclera immediately behind the attachment of bulbar conjunctiva Rectus muscles- responsible for axial movement of the eyeball Oblique muscles- responsible for rotatory movement of the eyeball Posterior rectus muscle- absent in man

17. Muscles of right eye as viewed from side

18. Nerve & blood supply Nerve supply Blood supply From ophthalmic arteries & veins No. Name Type Distribution II Optic Sensory Retina of eye III Oculomotor Motor All extra ocular muscles except superior oblique, lateral rectus & posterior rectus muscles IV Trochlear Motor Superior oblique muscle of eye VI Abducent Motor Retractor oculi & lateral rectus muscle of eye

19. Tunics of eye There are three coats (tunics) of the eye: Fibrous tunic or Tunica fibrosa (outer layer) - Cornea & Sclera Vascular tunic or Uvea - Choroid, Ciliary body & Iris - It provides nourishment to the eyeball Nervous tunic or Tunica interna (inner layer) - Retina - Formed by expansion of the optic nerve

20. Tunics of eye

21. A. Fibrous tunic Outer protective & hard coat of the eyeball The opaque (white) 5/6 th part- Sclera The anterior transparent 1/6 th part- Cornea The junction between sclera & cornea- Sclerocorneal junction ( Limbus )

22. 1) Sclera Opaque 5/6 th part Externally it is white & internal surface is brown Ocular muscles are inserted on outer surface of sclera Posteriorly pierced by- optic nerve, ciliary vessels & cililary nerves Optic nerve pierces the sclera- at the optic disc or blind spot of the eye

23. 2) Cornea Transparent & avsacular membrane Convex in front & concave behind It covers the iris, pupil & anterior chamber Also known as window of the eye Nocturnal animals- larger corneas- to allow more efficient light collection

24. The cornea consists of four distinct layers : The Anterior Epithelium, which is attached to its own basement membrane The Stroma, which makes up 90% of corneal thickness. It is made from keratocytes, uniform, parallel collagen fibrils (which form lamellae) and ground substance. Descemet’s Membrane, which is the basement membrane of the endothelium. It consists of a single layer of cells and does not stain with fluorescein. Therefore in corneal ulceration where all stroma is lost, it can appear as a dark structure in the centre . The Endothelium. Similarly to Descemet’s membrane it is only one cell thick and acts to move ions from the stroma to the aqueous

25. B. Vascular tunic This tunic remains between sclera & retina It consists of choroid, ciliary body & iris The uveal tract makes up the middle layer of the globe, and consists of the iris, ciliary body and choroid. It is usually pigmented and is the vascular layer of the globe. The anterior uvea includes the iris and ciliary body while the choroid comprises the posterior uveal tract.

26. 1) Choroid Dark colored thin vascular membrane It provides nutrition to the retina Tapetum lucidum Specialized structure produced by the choroid C ause the yellow-green glow when light hits an animal's eyes Present in nocturnal animals- Dogs, cats, horses & cows Absent- Pig, rabbit, birds & humans

27. 2) Cliliary body Anterior thickened part of choroid Supports the lens through zonules Major site for the production of aqueous Anterior portion consists of the ciliary muscle & the ciliary processes Posterior portion (pars plana) extends posteriorly to the choroid & retina Junction of ciliary body & retina- Ora serrata ( ora ciliaris retinae)

28. 3) Iris Muscular diaphragm between the cornea & lens Pupil- an opening in center of iris Shape of pupil Horizontally elliptical- horse, cattle, buffalo, goat & sheep Roundish- foals Circular- dog, donkey, birds & man Vertically elliptical- cat & fox Pupil constricts in bright light & dilates in dim light conditions

29. C. Nervous tunic Innermost tunic of the eyeball- Retina Membranous expansion of the optic nerve elements Also known as screen of eye Image is cast on it & converted to bio-electrical signal At the center of the posterior pole of eye retina presents oval yellow spot- Macula lutea Depression at the center of macula lutea - Fovea centralis (sense of vision is most acute)

30. Retina Nervous tissue in the eye, upon which the image is cast & converted to bio-electrical signal The rods & cones are involved in this biochemical transformation & the generated signal travels via the ganglion cells, & the nerve fiber layer to the optic nerve & onto the visual centers in the brain The number of rods (light sensitive) are 3 times more than cones (color sensitive) & are also more sensitive to light

31. Lens Biconvex transparent disc enclosed in a capsule Situated behind the pupil & in front of the vitreous body Chief refractory medium of the eyeball It allows the image to focus on the retina Kept in position by suspensory ligament It has no vessels or nerves, so nutrients are obtained from the aqueous humour , by diffusion Position of lens

32. The lens is a biconvex, transparent and refractive structure suspended by zonular fibers , situated behind the iris, dividing the anterior and posterior segments of the eye. The lens consists of a capsule, lens epithelium and the lens fibers . T he lens is subdivided into a central nucleus and surrounding cortex  It is held in position by lens zonules which originate on and between the ciliary processes of the ciliary body and insert onto the lens capsule

33. CHAMBERS OF EYE Aqueous humour Clear fluid- between cornea & lens (i.e. anterior chamber: between Iris &Lens i.e. Posterior Chamber) Provides nutrition to avascular cornea & lens Produced by ciliary processes of ciliary body Vitreous humour Clear gel- between lens & retina It helps to maintain shape & pressure of the eyeball It acts as a refractive medium

34. Aqueous humour & Vitreous humour