differenciate presbyopia and hypermetropia
- it the defect of a human eye, which is able to see far away object clearly but not the nearby objects.
- the correction lens for this defect is convex lens of suitable focal length or power.
1: decrease in length of thr eye ball.
2: increase in focal length of the eye lens.
- it is the defect of eye during old age, with increase of age the ciliary muscles holding the eye lens weaken and the eye loses some of its flexibility this causes presbyopia.
- the correction for this lens is a bifocal lens.
1: increase in focal length of eye lens.
2: old age.