Defects of Vision and their Correction

We can see that in normal eye the things taking part in refraction are the cornea, aqueous humour, crystalline eye lens and the vitreous humour. Let us assume that we consider only $2$ things namely the cornea and the eye lens. The power of the cornea is fixed and equal to $40 D$. The ciliary muscles can change the power of the eye lens which varies between $10 D$ to $20 D$. Calculate the least distance of distinct vision for such an eye.

The_____ lens power is used to correct astigmatism.

Myopia is corrected by wearing spectacles with a concave lens.

Myopia is due to

Describe myopia with the help of a ray diagram. Draw a ray diagram for the correction of myopia defect in the eye and explain the correction of myopia.

_____ surgery is the only treatment to potentially resolve astigmatism ?

 Laser surgery corrects the astigmatism permanently.This statement is true or false?

How is Astigmatism removed ?

What type of lens is present in human eyes?

Defect of vision which cannot be corrected by using spectacle:

The decrease in the power of accumulation of the eye with age is formed as

Astigmatism can be corrected by using _____.

A person can focus objects only when they lie between $0.5 \mathrm{m}$ and $3 \mathrm{m}$ from his eyes. What spectacles should he use to increase his maximum distance of distinct vision to infinity.

A presbyopic patient can see objects only when they lie between $50 \mathrm{cm}$ and $200 \mathrm{cm}$ from the eye. Then the focal length of the correcting lens required while reading is 

A myopic patient uses

Loss of ability of eye to focus on near and far object with advancing age is called

What is myopia? What is its remedy?

What focal length $\left(\mathrm{in} \mathrm{cm}\right)$ should the reading spectacles have for a person for whom the least distance of vision is $50 \mathrm{cm}$. (The distance of normal vision is $25 \mathrm{cm}$.)

Far point of a person is $150 \mathrm{cm}$. Calculate the focal length and power of a lens required to make him see correctly :-