Question

Bi-focal lens is used to correct ____________ refractive error.

Answer 1

$\Huge\mathcal{Hey!}$

Bi-focal lens is used to correct presbiopia

Answer 2

AnsWer :

▶ Bi-focal lens is used to correct Presbyopia refractive error.

ExplanaTion :

$\boxed{\sf{\pink{\large{Presbyopia :}}}}$

• In this refractive error both near and far objects are not clearly visible.
• i.e. far point is lesser than infinity and near point is greater than 25cn.
• It is an old age disease as at old age ciliary muscles lose their elasticity and can not change the focal length of eye-lens effectively.
• Hence eye loses its power of accommodation.

☀ Some other eye defects :-

• Myopia
• Hypermetropia
• Astimatism