Question

What is a long-sighted eye? State one cause of long sightedness. Name the lens used for correcting long-sightedness.

Answer 1

Hint:We know that the hypermetropia or long-sightedness of a person cannot see nearby objects clearly but can see distant objects. The converging power of eye-lens in this defect increases this will result in the formation of the distant object behind the retina.

Complete answer:
As we know, the defect of vision in human eyes in which a person cannot see nearby objects clearly but can see distant objects. Hence, it is also called long-sightedness. In hypermetropia near the point of the eye that is more than \[25\] centimeters away it is opposite to myopia. Long-sightedness is the inability of the eye to focus on an object which is kept near the eye. It is also called hyperopia.

In long-sightedness there is no difficulty to focus on the object which is kept at a long distance. The ability to view nearby objects requires a different lens shape and as we know that the focal length of the eye depends on the aperture of the eye - a shape that the farsighted eye is unable to assume.

Subsequently, the Long-sightedness eye is unable to focus on nearby objects. Due to inability to accommodate the eye can no longer assume the high curvature that is required to view nearby objects. The lens' power to refract light has diminished and the images of nearby objects are focused at a location behind the retina.

The eye is said to be long-sighted, if the image of a nearby object is formed in front behind the retina. It is caused because the eye lens cannot widen enough to reduce the focal length i.e., it is too thin or if the cornea is small.

Note:Remember that the synonyms of long-sightedness and short-sightedness, it is a common mistake to understand that short-sightedness means a defect of vision in which something is wrong in the near point of the eye and the vice versa for the Hypermetropia.