You all must have heard about or must have seen some people who look obliquely, as if there is some defect in their eyes. Some people inhumanly call them "bhenge", this condition is Astigmatism.
What is Astigmatism?
Astigmatism is a condition in which light rays are not brought to a sharp point upon the retina. This defect is normally present in all the eyes. When it is moderate, it is known as "physiological astigmatism". When it is well maked, it is considered abnormal.
Causes of Astigmatism
If the curvature of eye ball is different in different meridians , vertical, horizontal, oblique, the refractive power of the eye lens will also be different in different meridians. The meridians with greater curvature reflects the light more strongly than the other meridians.
So these light rays are brought to a focus in front of the light rays, which pass through other meridians.
Types of Astigmatism
There are two types of Astigmatism:
1. Regular Astigmatism
2. Irregular Astigmatism
Regular Astigmatism: The refractive power is unequal in different meridians because of alteration of curvature in one meridian. But it is uniform at all points in the affected meridian.
Irregular Astigmatism: In irregular types of Astigmatism, the refractory power is not only unequal in different meridians but also different at different points of the affected meridian.
Correction of Astigmatism
Astigmatism is corrected by the cylindrical lens which have convexity in all the meridians, corresponding to that of lens of eye having a lesser curvature that is if the curvature of the lens is horizontal which is less, the person should use cylindrical lens having convexity in the horizontal direction.
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