Enumerate the various eye defects. Comment on corrective measures.
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The common eye defects are as follows:
Myopia or shortsightedness- it takes place when the eye ball is too long in comparison with the cornea and lens of the eye. This causes the light rays to focus at a point in front of retina and not over it. The nearsighted number glasses are preceded by a (-) sign. It is corrected using concave lens
Hypermetropia or longsightedness- Here the vision problems will occur when the light rays will focus at a point behind the retina. The eyeballs are shorter and it is difficult to see the nearby objects. The farsighted glasses are preceded by (+) sign. It is corrected using convex lens.
Astigmatism- in astigmatism, the eyeball is shaped like a rugby ball with one meridian being extra curved than the other meridian. Astigmatism causes the vision to be blurred in all distances. So it is usually a combination of myopia and hypermetropia. It uses both concave and convex.
Presbyopia- It normally stems from a gradual thickening and inelasticity of the natural lens of the eyes. This usually happens around the age of 40.
Myopia or shortsightedness- it takes place when the eye ball is too long in comparison with the cornea and lens of the eye. This causes the light rays to focus at a point in front of retina and not over it. The nearsighted number glasses are preceded by a (-) sign. It is corrected using concave lens
Hypermetropia or longsightedness- Here the vision problems will occur when the light rays will focus at a point behind the retina. The eyeballs are shorter and it is difficult to see the nearby objects. The farsighted glasses are preceded by (+) sign. It is corrected using convex lens.
Astigmatism- in astigmatism, the eyeball is shaped like a rugby ball with one meridian being extra curved than the other meridian. Astigmatism causes the vision to be blurred in all distances. So it is usually a combination of myopia and hypermetropia. It uses both concave and convex.
Presbyopia- It normally stems from a gradual thickening and inelasticity of the natural lens of the eyes. This usually happens around the age of 40.
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