ASTIGMATISM
in Astigmatism light rays from an object do not focus to a single point because of variations in the curvature of the cornea or lens at different meridians. Instead, there is a set of 2 focal lines . To correct astigmatism a cylindrical lens is used which has a line in lens in refraction box set. Both type of cylindrical lens are present convex and concave.
TREATMENT
In children more than 1.5 diopter astigmatism is corrected. In case of squint full cycloplegic refraction is given.
Types of astigmatism
simple myopic astigmatism: if one focal line is in front of retina and one is on retina
compound myopic astigmatism: if both focal lines lie in front of retina
simple hyperopic astigmatism: if one line is behind retina and other is on retina
compound hyperopic astigmatism: if both lines are behind retina
mixed astigmatism: if one line is in front and other is behind retina