1.

Enumerate the common defects of vision, their causes and the possible methods of correcting them.

Answer»
Defect of visionCauseCorrective measure
MyopiaLengthening of eye ball from front to back or the lens is too curved.Using suitable concave lens
HyperopiaShortening of eye ball from front to back or the lens is too flat.Using suitable convex lens
AstigmatismUneven curvature of the corneaUsing suitable cylindrical lenses
PresbyopiaLoss of flexibility of lensUsing suitable convex lens
CataractLens turning opaqueSurgery or use of convex lens or implantation of plastic lens.
Colour blindnessGenetic defectNo control measure
SquintFormation of cross-eyeSurgery and suitable exercise



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