MCQ Detailed View

Myopia, commonly known as short-sightedness or near-sightedness, is a common defect of vision where a person can see nearby objects clearly but has difficulty seeing distant objects. This defect occurs because the image of distant objects is focused in front of the retina, instead of directly on it. The main reason for this is either:

1. 
   

   Elongation of the eyeball (the eye is too long from front to back), or

   
   


2. 
   

   Excessive curvature of the eye lens, making it too powerful to focus light correctly.

   
   

To correct myopia, diverging lenses are used. These are concave lenses, which have thinner centers and thicker edges. When light rays from distant objects pass through a concave lens, they are diverged slightly before entering the eye. This allows the eye’s natural lens to focus the rays correctly onto the retina, resulting in a clear image.

A convex lens, on the other hand, converges light rays and is used to correct hypermetropia (long-sightedness), not myopia. A cylindrical lens is used for astigmatism, a condition caused by uneven curvature of the cornea. A plano-convex lens has limited applications in optics but is not used in vision correction.

Concave lenses used for myopia are usually specified by their negative focal length or negative diopter value (e.g., -1.5D). Eyeglasses or contact lenses with concave lenses are prescribed after an eye test to match the individual’s level of myopia.

This concept is part of physics, specifically under optics, as it explains how light rays behave and how corrective lenses adjust their path. Understanding this principle is crucial in learning how vision works and how optical devices help overcome natural defects of the human eye