Question

defect of vision explain

Answer 1

The most common types of eye defects are as follows:-

1.MYOPIA or NEARSHIGHTED

Myopia occurs when the eyeball is too long, relative to the focusing power of the cornea and lens of the eye. This causes light rays to focus at a point in front of the retina, rather than directly on its surface If you're nearsighted, the first number ("sphere") on your eyeglasses prescription will be preceded by a minus sign (–). The higher the number, the more nearsighted you are.

2.HYPEROPIA or FARESIGHTED

This vision problem occurs when light rays entering the eye focus behind the retina, rather than directly on it. The eyeball of a farsighted person is shorter than normal

Farsightedness can be corrected with glasses to change the way light rays bend into the eyes. If your glasses begins with plus numbers, like +1.50, you are farsighted.

3.ASTIGMATISM

Instead of the cornea having a symmetrically round shape (like a tennis ball), it is shaped more like a rugby ball, with one meridian being significantly more curved than the meridian perpendicular to it

Astigmatism usually causes vision to be blurred or distorted to some degree at all distances. Symptoms of uncorrected astigmatism are eye strain and headaches, especially after reading or other prolonged visual tasks

Astigmatism is usually combined with Myopia or Hyperopia.

4.PRESBYOPIA

Presbyopia generally is believed to stem from a gradual thickening and loss of flexibility of the natural lens inside your eye

Presbyopia usually occurs beginning at around age 40, when people experience blurred near vision when reading, sewing or working at the computer. Everyone becomes presbyopic.

Answer 2

$\large\bf{\underline{Here\: is\: your \:answer:-}}$

$\sf{\underline{The\: main\: defects \:of\: vision\:are:-}}$

✔️ Myopia.
✔️ Hypermetropia.
✔️ Presbyopia.

$\bf{\large{Myopia}}$

Myopia is also known as near-sightedness. A person with Myopia can see nearby objects clearly but cannot see distant objects distinctly.

This defect arises due to :-
⏩ Excessive curvature of the eye lens.
⏩ Elongation of the eyeball.

This defect can be corrected by using a concave lens of suitable power.

$\bf{\large{Hypermetropia}}$

Hypermetropia is also known as far-sightedness. A person with hypermetropia can see distant objects clearly but cannot see near by object distinctly.

This defect arises due to:-
⏩ The focal length of the eye lens is too long.
⏩ The eyeball has become too small.

This defect can be corrected by using a convex lens of appropriate power.

$\bf{\large{Presbyopia}}$

The power of accommodation of eyes usually decreases with ageing. They find it difficult to see nearby objects comfortably and distinctly without corrective eye-glasses. This defect is called Presbyopia.

This defect arises due to:-
⏩ Gradual weakening of ciliary muscles.
⏩ Diminishing flexibility of the eye lens.

This defect can corrected by using bi-focal lenses consists of both concave and convex lenses.

$\huge\mathfrak\red{Hope\:it \:helps\: you}$