Human eye and the colorful world

Starting with Eye defects since test tmrw, will build upon later

What are the three main eye defects?

• Myopia

• Hypermetropia

• Presbyopia

How can these defects be corrected?

• By the use of suitable spherical lenses

Myopia

• A common vision condition also known as nearsightedness, where distant objects appear blurry while close objects can be seen clearly.

• In a myopic eye, the image of a distant object is formed in front of the retina and not at the retina itself

Causes of Myopia

• Excessive curvature of the eye lens

• Elongation of the eyeball

How can myopia be corrected?

• By using a concave lens of suitable power

Hypermetropia

• A vision condition also known as farsightedness, where distant objects can be seen clearly while close objects appear blurry.

• In a Hypermetropic eye, the image of a nearby object is formed behind the retina.

Causes of Hypermetropia

• The focal length of the eye lens is too long

• The eyeball has become too small

How can Hypermetropia be corrected?

• By using a convex lens of appropriate power

Why are convex lens suitable for hypermetropia?

• Converging lenses provide the additional focusing power required for forming the image on the retina

Why are concave lenses suitable for myopia?

• A concave lens of suitable power will bring the image back on to the retina and thus the defect is corrected

Presbyopia

• A vision condition that typically occurs with aging, leading to a gradual loss of the ability to see things clearly up close.

• The power of accommodation of the eye usually decreases with ageing being the primary cause for Presbyopia.

• It arises due to the weakening of the ciliary muscles and diminishing flexibility of the eye lens

On what occasion would a person require bi-focal lenses?

• Sometimes a person may suffer from both myopia and hypermetropia.

• Such people often require bi-focal lenses

What is a common type of bi-focal lenses?

• A common type of bi-focal lenses consists of both concave and convex lenses.

• The upper portion consists of a concave lens. It facilitates distant vision

• The lower part is a convex lens. It facilitates near vision