2. What is the function of this chart ?

3. What eye defect you may suffer if you see the distant object like this?

4. Eye Defects & Their Corrections Short Sight Long Sight Colour Blindness

5. Short Sight Light rays from DISTANT DISTANT object DISTANT Definition: The image of DISTANT IN FRONT OF object falls IN FRONT OF the retina.

6. Causes of Short Sight: Corrections: CONVEX 1.The lens is too CONVEX. LONG 2.The eye ball is too LONG. CONCAVE Wearing CONCAVE (diverging) lens diverge → diverge the light rays from the distant object onto the retina.

7. Corrections of Short Sight Light rays from DISTANT DISTANT object Concave lens Light rays are diverged Sharp image

8. Long Sight Light rays from NEAR NEAR object NEAR Definition: The image of NEAR object BEHIND falls BEHIND the retina.

9. Causes of Long Sight: Corrections: THIN 1.The lens is too THIN. SHORT 2.The eye ball is too SHORT. CONVEX Wearing CONVEX (converging) lens converge → converge the light rays from the near object onto the retina.

10. Corrections of Long Sight Light rays from NEAR NEAR object Convex lens Light rays are converged Sharp image

11. Colour-blindness Write down what you see in each of the following chart!! a.

12. b.

13. c.

14. d.

15. Chart Vision a.b.c.d. Normal 2945  26 Red-green colour-blindness 70  52 or 6 Total colour- blindness  Are you suffering from colour- blindness?

16. Causes of Colour blindness: Types of Colour blindness: 1.It is due to the absence of certain kind of cone cells. hereditary 2.It is a hereditary defect. So, it cannot be corrected by wearing glasses. Redgreen 1. Red-green colour blindness. 2. Total colour blindness.