1. Eye: Anatomy and Physiology of Vision Nestor T. Hilvano, M.D., M.P.H. (Illustrations Copyright by Frederic H. Martini, Pearson Publication Inc., and The McGraw-Hill Companies Inc.)

2. Learning Objectives 1.Describe the structures and functions of the eyelids, tarsal glands, and lacrimal apparatus of the eye. 2.Discuss the internal structures and functions of the eye noting the 3 distinct tunics, optic disc, chambers, and refractive media. 3.Explain how do you able to distinguish light and color perceptions. 4.Describe accomodation and its visual abnormalities. 5.Describe conjunctivitis, chalazion, sty, cataract, and glaucoma. 6.Trace the visual pathway from the field of vision to the brain.

3. Accessory Structures of Eye provide support, protection and lubrication Eyelids (palpebrae) –consist of skin, orbicularis oculi muscle and tarsal plate –Eyelashes –Tarsal glands Superficial epithelium – palpebral (inner surface of eyelids) and bulbar (anterior surface of eye) conjunctiva Lacrimal apparatus

4. Lacrimal Apparatus Lacrimal gland – produces 1 ml. tears/day Tears contain lysozyme Lacrimal gland with ducts Lacrimal canaliculi Lacrimal sac Nasolacrimal duct

5. Tunics of the Eyeball Outer or Fibrous layer - C________ and S_________ Middle or Vascular layer (uvea) - I_____, C____ and C_____ Internal or Nervous layer - R________.

6. Iris

7. Optical Components: Refractive Media refract light to focus on retina C_______ = transparent cover on anterior surface of eyeball A_______ = serous fluid posterior to cornea, anterior to lens L______ = changes shape to help focus light V______ = jelly fills space between lens and retina

8. Clinical Consideration C__________ = clouding of lens –aging, diabetes, smoking, and UV light G__________ = death of retinal cells due to elevated pressure within the eye C__________ = infection of tarsal gland (meibomian gland). S__________ = infection of small tarsal glands (zeis gland) that open to the surface between the hair follicles. C__________ = pink eye, results from damage or irritation of conjunctival surface. Diabetic retinopathy – leading cause of blindness in US

9. Neural Tunic Retina = forms as an outgrowth of the diencephalon - attached at optic disc and at ora serrata Opthalomoscopic exam - Macula lutea = fovea centralis - Optic disc: __________ Light passes through lens to form inverted image on retina Where is the site of sharpest vision?

10. Histology of Retina Pigment epithelium –absorb stray light and prevent reflections Photoreceptors –R____ cells (scotopic vision; 125 M) –C_____ cells (photopic vision; 6 M ) Bipolar cells Ganglion cells Horizontal and amacrine cells

11. Refraction Visual acuity – clarity of vision, normal is 20/20 Bending of light rays occurs when light passes through refractive index

12. Accommodation of Lens The lens thicken to focus the image of a nearby object. The lens thin out when focus on a distant object.

13. Accomodation Problems Hyperopia = farsighted; eyeball small; corrected with convex lenses * Presbyopia = in elderly due to ___________________________. Myopia = nearsighted; eyeball large; corrected with concave lenses Astigmatism = light passing through is not refracted properly Scotoma = abnormal blindness on field of vision at positions Floaters = temporary resulting from blood cells or cell debris in the vitreous body.

14. Color Vision Color vision – integration of information of red, green and blue Color perception based on mixture of nerve signals Color blindness = hereditary lack of one photopsin - ex: on testing, lacking populations of cones can’t distinguish the pattern image (the number 12) - red-green is common sex-linked recessive

15. Visual Pathway Vision – is the perception of light reflected from objects in the environment Rods and cones cells in retina - 1 st and 2 nd order neurons Optic nerve, optic chiasma, optic tract 3 rd order neurons in Lateral geniculate nucleus form optic radiation to 1  visual cortex Few fibers project to superior colliculi and midbrain for visual reflexes

16. Homework 1.Define key terminologies: fovea, optic disc, sty, chalazion,visual acuity, accomodation, presbyopia, visual acuity, rods, and cones. 2.Give the function/s of the following: a) cornea, b) ciliary body, c) choroid, d) lens 3.Identify the conditions associated below: a) blockage of canal of schlemm, b) opacity of lens, c) inelasticity of lens in elderly, d) vitamin A deficiency, e) pink eye 4. Compare and contrast myopia and hyperopia as to visual problems, shape of eyeball, and focus of vision on retina. 5. Trace the visual pathway from photoreceptors to visual cortex.