Question

A defect of vision caused due to excessive curvature of the cornea is:
A. myopia
B. hypermetropia
C. astigmatism
D. presbyopia

Answer 1

Hint: We know that the human eye is a complex organ, which is sensitive to light and provides vision. The eyes may also have a few defects like myopia, hypermetropia , astigmatism and presbyopia. Some of which can be corrected using appropriate lenses.

Complete step-by-step answer:
The eyes contain various parts, whose functions are as given below:
1. Cornea, it is transparent covering of the eyes. It is the outermost covering of the eyes, and thus protects the eyes from minor damages.
2. Iris is a thin substance which controls the diameter of the pupil.
3. Pupil, which regulates the light entering the light by relaxing and tightening the muscles around the iris.
4. Lens, the eyes has a bi-convex lens which helps is the focusing of the light onto the retina.
5. Retina is a screen to which the light entering the pupil is projected.
6. The cones are responsible for the identification of colour and the rods are helpful in seeing things during night. Both transfers signal the brain.

The loss of sight or slow degradation of sight is due to aging or damage in the eyes. One of the major eye defects is Myopia. Also known as near-sightedness happens when the eyeball of the retina is elongated. This results in the excessive curvature of the cornea. This results in the reduced ability to see the faraway objects clearly. However this can be corrected by wearing appropriate spectacles.

So, the correct answer is “Option A”.

Additional Information: Other eye defects include:
1. Hypermetropia: It is also known as the far-sightedness. Here one will be unable to see the near-by objects clearly. This is mostly seen in young age. It is due to inflexibility of the cornea. This can also be corrected by wearing appropriate spectacles.
2. Astigmatism: Here the objects become blurry and hazy, this is due to the improper spherical curvature of the cornea. This can also be corrected by wearing appropriate spectacles.
3. Presbyopia: It is predominantly due to aging, here the elasticity of the lens is lost and thus the focusing of the eyes decreases gradually.

Note: The above eye defects are due to the lens and not the eyes itself, hence they can be corrected by wearing spectacles of appropriate focal lengths. However, if there is any trouble with the retina then the person is visually blind.