The document summarizes the refractive media of the eye, including the cornea, aqueous humor, lens, and vitreous humor. It describes their refractive indices, roles in focusing light, and contributions to the eye's total refractive power. It also discusses accommodation and errors of refraction like myopia and hyperopia.

1. VISION; Refractory Media of the Eye Dr. Nisreen Abo-elmaaty Physiology Department

12. The Optical System of the Eye The divergent light rays must pass through an optical system that brings them back into focus. The cornea & lens is the optical system of the eye that focus light rays onto the retina

22. The lens becomes more spherical during near vision (contraction of ciliary muscle)

24. Pathway of Accommodation reflex:

26. 1 100 60 5 50 40 7 20 30 10 14 20 14 10 10 Amplitude of Accommodation (dioptres) Nearest point (cm) Age (years)

29. Myopia (short sight)

30. Hypermetropia (Long sight)

31. Errors of Refraction

32. Cylindrical lens in suitable plane Contact lens. Biconvex lens ( ↑ refractive power) Biconcave lens (diverge) ttt - Unequal curvature of cornea or lens. -short eye ball - Weak lens -long eye ball -Strong lens Cause Focus of rays in one plane is at different distance from that of rays in another plane. Focus behind retina Focus in front of retina Defect Astigmatism Hypermetropia Myopia

39. The Visual Field

41. GOOD LUCK