The common eye sight defects are
1. Myophia: It is commonly called as Short Sight. This defect is due to either bulging of eye ball or increased convexity of the eye lens. It can be corrected by wearing artificial concave lens.
2. Hypermetropia: This is commonly called as Long Sight. It is caused due to either flattening of eye ball or decreased convexity of the eye lens. Correction of the long sight can be done by wearing artificial convex lens to the eyes.
3. Presbyopia: This is commonly occurs to the old age group people. This defect is caused due to loss of elasticity of eye lens.
4. Nyctolopia: This is commonly termed as Night Blindness. The person who is suffering from night blindness cannot see in dim light. This is due to deficiency of Vitamin-A.
5. Cataract: Opacity of the eye lens is termed as cataract. This is due to degenerative changes in the eye lens.