Question

Name the three common defects of vision. What are their causes? Name the type of lens used to correct each of them.

Answer 1

(i) Myopia: 

Cause: Elongation of eyeball, Type of lens used for correction: Concave lens of suitable power. 

(ii) Hypermetropia: 

Cause: Shrinking of eyeball, Type of lens used for correction: Convex lens of suitable power. 

(iii) Presbyopia: 

Cause: Weakening of ciliary muscles, Type of lens used for correction: Bifocal lens.