Question

Which defect of the eye can be corrected by using a cylindrical lens?

Answer 1

We know that the defects of the eye can be corrected by using different types of lenses. For example, if a person has a defect in which he can only see things closer to him, then this defect is known as the “Myopia,” and in order to correct this defect, we use the “Concave Lenses.”

Complete answer:
The type of lens given is a cylindrical lens. Cylindrical lenses are used to focus the light in the form of a line and the curved surface of these types of lenses is the same as a cylinder. These lenses focus the light only in one dimension in the form of a straight line and are mainly used to change the aspect ratio of an image by either stretching or contracting the image. That is why they are called the cylindrical lenses.
If a person is suffering from an “Astigmatism” defect, then the cylindrical lenses are used to correct this defect. In this defect, the eye of the person is not able to focus the light evenly on the retina. Because of this, the image captured by the retina appears blurry and the person cannot see the horizontal and vertical lines clearly. So, the cylindrical lenses help the person by changing the focus of the light on the retina. Also, this defect is worsened for the person with an improper spherical eye lens.

**Therefore, we can say that the defect of the eye that can be corrected by using a cylindrical lens is Astigmatism.

Note:**
The shape of the cylindrical lens is always flat cylindrical, but it also depends upon the condition of the defect and the shape of the cornea. The cornea is the front part of the eye and the shape of it changes because of Astigmatism defect.