What is presbyopia (old sisght)? Is this a combination of both short and long sightedness?
Presbyopia is the defect of eye in which a person cannot see further as well as nearer objects clearly. This defect of vision commonly occurs to old people because of the:
1. weakening of the ciliary muscles
2. reduction in the flexibility of the eye lens
This type of defect can be corrected by using bi-focal lenses. A bifocal lens consists of both convex lens (to correct hypermetropia) and concave lens (to correct myopia).