Question

Explain different types of vision defects and their rectification.

Answer 1

Following are the vision defects and their rectification :

• Myopia : When a person finds it difficult object, he suffers from near sightedness or myopia. Myopia happens because of increased curvature of lens. In this case, image of a distant object is formed before the retina. This defect is rectified by using a concave lens of suitable focal length. The lens helps in making the image on retina.
• Hypermetropia : When a person finds it difficult to see nearby objects, he suffers from far sightedness or Hypermetropia. This defect happens because of reduced carvature of lens. In this case, image of a nearby object is formed behind the retina. This defect is rectified by using a convex lens of suitable focal length.
• Presbyopia : Again results in weak ciliary muscles. This reduces the power of accommodation of eyes. As a result, the person finds it difficult to see nearby as well as distant objects. This defect is rectified by using bi-focal lens.
• Astigmatism : This condition develops because of irregular curvature of cornea. A person suffering from this defect is unable to differentiate between vertical and horizontal planes. This defect is rectified by using cylindrical len