ANATOMY & PHYSIOLOGY OF EYE.pptx

A short simplified anatomy of eye. it includes explanation of all 3 layers of eyes, sclera, choroid and retina. Anatomy of cornea, conjunctiva, pupil, lens, iris, ciliary body etc. physiology of vision, its process and photochemical activity of eyes are discussed in detail.

1. ANATOMY OF EYE BY : MS SAILI GAUDE PRINCIPAL SHIVAM COLLEGE OF NURSING AMIRGADH

2. EYES Also called sensory organ of sight or vision Photo receptor organ 2 eyes Spherical in shape 2.5 cm in diameter Lies in a ball shaped cavity of skull called the orbit

3. Supplied by optic nerve Medical speciality related to study of eye and its disorder is called optholomology Six set of muscles attached to it: 4sets straight muscles :Superior , inferior, medial and lateral. 2 sets oblique muscles : superior and inferior Both eyes are anatomically separate but functions as a pair through co-ordination.

4. STRUCTURE OF EYEBALL Hollow sphere Consists of 3 layers called as tunics 1) outer fibrous layer- sclera, cornea and conjunctiva 2) Middle vascular layer- Choroid, cilliary body and Iris 3) Inner layer -Retina

5. OUTER FIBROUS LAYER Sclera: white part of eye Opaque layer extending posteriorly over 5/6 th outer layer of eyeball Made up of strong non elastic fibrous connective tissue Gives eyeball its shape Protects inner layers of eyeball. Thinnest anteriorly and thickest near the entry of optic nerve

6. OUTER SURFACE OF SCLERA White and smooth Anterior part covered with conjunctiva

7. INNER SURFACE OF SCLERA Brown and grooved for ciliary nerves and vessels Separated from choroid by the perichoroidal space

8. CANAL OF SCHLEMM Sclera is continuous anteriorly with the cornea at the sclerocorneal junction. The deep part of this are have a circular canal known as the canal of Schlemm The acqueous humor drains into the anterior sclera and ciliary veins through this sinus

9. CORNEA Sclera slightly bulges anteriorly which is called cornea It is transparent It is non vascular Acts as a non adjustable lens through which light enters into the eyeball A thin transparent membrane behind the eyelids called conjunctiva terminates into the cornea.

10. The junction with sclera is called sclerocorneal junction More convex than sclera Separated from iris by a space called as anterior chamber Cornea is avascular and is nourished by lymph which is circulated in numerous corneal spaces and by lacrimal fluid. Supplied by branches of opthalmic nerve and short ciliary nerves Pain arises from cornea

11. CONJUNCTIVA Tissue that lines eyelids and covers the sclera Composed of non keratinized cells: Stratified squamous epithelium with goblet cells, Stratified columnar epithelium and Stratified cuboidal epithelium

12. Highly vascular tissue, with many microvessels Can be divided into 3 regions Palpebral conjunctiva Bulbar conjunctiva Conjunctival fornices

13. Palpebral conjunctiva- lines the eyelids Further divided into marginal, tarsal and orbital Bulbar conjunctiva- found on the eyeball over the anterior sclera Further divided into scleral part and limbal part Conjunctival fornicate are further divided into superior, medial, lateral and inferior region.

14. FUNCTIONS OF CONJUNCTIVA Provides protection and lubrication of eye by production of mucus and tears Prevents entry of microbes Play a role in immune surveillance Lines inside of eyelids Provides covering to sclera Highly vascularized Many lymphatic vessels

15. MIDDLE VASCULAR LAYER

16. CHOROID Middle layer of tissue in wall of the eye Found between sclera and retina Thin pigmented layer Its attachment to sclera is loose so it can be easily separated from it The inner surface of choroid is firmly attached to retina

17. FUNCTIONS OF CHOROID Providing nutrients for retina, macula and optic nerve Regulates temperature of retina Helps control pressure within the eyes Absorbs light and limits reflections within eyes that can harm vision

18. CILIARY BODY Circular structure that is an extension of the iris Produces the fluid in the eye called aqueous humor Also contains ciliary muscle Ciliary muscles helps change shape of lens when eyes focus on a near object

19. IRIS Colored part of the eye Controls the amount of light that enters into the eye It is the most visible part of the eye Lies in front of lens Separates anterior chamber from posterior chamber Contraction and relaxation of iris is a reflex action

20. The colour of iris is determined by the number of pigment cells in its connective tissue If pigment cells are absent, the iris is blue in colour

21. PUPIL Dark centre opening in the middle of iris Pupil changes size to adjust amount of light entering the eyes So pupils constricts (becomes small) in bright light and becomes dilated (bigger ) when there is dim lighting.

22. LENS It is elastic, colorless and transparent Biconvex body made up of epithelial cells Lies posterior to iris Lens can accommodate and change its shape, focusing on different objects at different distances ie . the lens is adjustable. This accommodation is brough by ciliary muscles Accomodation is the process by which our eyes can see near and far objects clearly

23. RETINA Multilayered Light sensitive mebrane Innermost layer of eyeball Connected to brain by optic nerve Consists of thicker neural layer called neural retina Thinner pigmented layer

24. The retina receives the focused light waves and transduces them into the nerve impulses that the brain converts into visual perceptions The portion of retina where the optic nerve exits from the eyeball and contains no photorecpetors is called the blind spot or optic disk This spot is not sensitive to light

25. PHOTORECPETORS OF RETINA 1) RODS 2)CONES

26. RODS Rods are sensory cell of perception of black and white shades Functions in dim light and helps in night vision Contains photosensitive pigment called rhodopsin synthesized from vitamin A Contains a photosensitive pigment called rhodopsin

27. CONES Cones are sensory cells for perception of colours Functions in bright light and differentiates color Contains photosensitive pigment called iodopsin They are also present in the rod free area of a small depression called as fovea centralis

28. MACULA LUTEA Most cones are concentrated in the centre of retina directly behind the lens in an area called macula lutea or yellow spot. It lies posteriorly lateral to optic disc It is avascular (no blood vessel) Yellow in colour

29. FOVEA CENTRALIS Centre of macula there is a small depression called fovea centralis Thinnest part of retina Contains only cones Site of maximum acuity

30. BLOOD SUPPLY Arterial- central artery Cones and rods: supplid by diffusion from capillaries of the choroid Veins: retinal veins

31. CHAMBERS OF EYEBALL ACQUEOUS HUMOR VITEROUS HUMOR

32. AQUEOUS CHAMBER Region between cornea and lens is the aqueous chamber Further divided into anterior chamber and posterior chamber Anterior chamber- between cornea and iris Posterior chamber- iris and lens Aqueous humor- thin, watery fluid containing amino acids, glucose ascorbic acid, hyaluronic acid and respiratory gases.

33. FUNCTIONS OF AQUEOUS HUMOR Nourishes the lens and cornea Refracts light rays to focus on retina Maintains constant pressure within eyeball

34. VITEROUS CHAMBER Largest chamber in the eyeball Occupies 80 % of the eyeball Present between lens and retina More viscous , jelly like or gelatinous Contains salts and muco proteins

35. FUNCTIONS OF VITEROUS HUMOR Stops eyeball from collapsing Supports retina Refracts light to focus on retina

36. OPTIC NERVE A bundle of more than a million nerve fibres which carry visual messages from the retina to the brain Brain actually controls what you see as it combines images The retina sees image upside down, but brain turns images right side up Like a mirror image Glaucoma is increase in the pressure inside the eye which can cause optic nerve damage.

37. EYELIDS Anteriorly, the eyes are protected by the eyelids Two canthus or commissure- lateral and medial Eyelids are made up of many layer starting from skin, subcutaneous tissue, orbicularis oculi , orbital septum and tarsal plate and palpebral conjunctiva

38. LACRIMAL APPRATUS Consists of lacrimal gland and the lacrimal sac with its ducts Lies in orbit above the eyes Produces tears that flows over the eyes when the eyelids are blinked Tears keeps the eye’s surface moist and lubricated Tears protects the eyes from infections and foreign body Chemical and mechanical irritants cause over secretion by the lacrimal glands to wash the irritants away Humans are the only species that form tears in response to emotions

39. EYELASHES Projecting from border of each eyelids are eyelashes

40. TARSAL GLANDS Modified sebaceous glands associated with eyelids edges are tarsal glands These produce an oily secretion that lubricates the eye. These are modified sweat glands that lie between the eyelashes

41. EXTRINSIC EYE MUSCLE Six extrinsic muscles or external, eye muscles are attached to the outer surface of the eye. These muscles produce gross eye movements and make it possible for the eyes to follow a moving object 1) lateral rectus 2) medial rectus 3) superior rectus 4) inferior rectus 5) superior oblique 6) inferior oblique

42. PHYSIOLOGY OF VISION Vision consists of the following steps 1) Refraction of light entering the eye 2) Focusing of image on retina by accommodation of lens 3) Convergence of image 4) Photo chemical activity in retina and conversion into neural impulse 5) Processing in brain and perception

43. 1) REFRACTION OF LIGHT ENTERING THE EYE Light travels parallel to Each other but they bend when they pass from one medium to another. This phenomenon is called refraction of light Before reaching retina it passes through cornea, aqueous humor, lens, vitreous humor so refraction takes place in every medium before it falls on retina Light is focused on the retina

44. 2)ACCOMODATION OF LENS TO FOCUS IMAGE A reflex process to bring light rays from object into perfect focus on retina by adjusting the lens. When an object lying less than 6 mts away is viewed, image is formed behind the retina. To prevent this the lens changes its shape to accommodate and form the image on the retina. Thus we can see the image properly

45. To accommodate to see close objects the ciliary muscles contracts The lens becomes thick due to this contraction thus focusing the object on the retina To accommodate to see far objects the ciliary muscles relaxes The lens becomes thin again due to this relaxation thus focusing the object on the retina Normal eye is able to accommodate light from object about 25 cm to infinity

46. 3)CONVERGENCE OF IMAGE Human eye have binocular vision It means we have 2 eyes but we perceive single image The two eyeball turns slightly inward to focus a close object so that both image falls on corresponding points on the retina at same time. This phenomenon is called as convergence.

47. 4. PHOTOCHEMICAL ACTIVITY IN RETINA AND CONVERSION INTO NEURAL IMPULSE Photochemical activity in rods: 125 million rods located in neuro retina Pigment present in rods- rhodopsin Rhodopsin- scotopsin + Retinene Retinene – carotenoid molecule and derivative of vitamin A 2 forms of retinene (retinal) exists- cis and trans

48. The extracellular fluids surrounding rod cells contains high Na+ ion and low concentration of K + ions while concentration of Na+ is low and K+ is high inside rod cells. The concentration is maintained by Na-K pump In resting phase K+ tends to move outside the rod cells creating slightly negative charge inside.

49. FLOW CHART OF PHOTOCHEMICAL ACTIVITY OF RODS

50. PHOTOCHEMICAL ACTIVITY IN CONES 7 million cones in each eye 3 different types of cone cells and each cone cells contains different photo pigment and are sensitive to red, green and blue. Cone cell pigment – idopsin composed of 11 cis retinal and photopsin Perception of color depends on which cones are stimulated Final perceived color is combination of all 3 types of cone cell stimulated depending upon the level of stimulation Proper mix of all 3 colour produce the perception of white and absence of all colour produces perception of black

51. 5. PROCESSING OF IMAGE IN BRAIN AND PERCEPTION All visual information originates in retina Retina consists of 5 types of cells: 1) Photoreceptor cells (rod and cones) 2) Bipolar cells 3) Ganglion cells 4) Horizontal cells 5) Amacrine cells

52. Photoreceptor cells, bipolar cells and ganglion cells transmits impulse directly from retina to the brain The nerve fibre of ganglion cells from both eye carries impulse along the nerve Optic nerve meets at optic chiasma where fibers from nasal half of retina cross over but fibers from temporal half of each retina does not cross over The optic nerve after crossing over is called optic tract Optic tract synapse – neurons of thalamus (lateral geniculate body ) – projection to primary visual cortex- occipital lobe- perception of vision

53. THE END