Q101
General ScienceBiology
Cause of myopia is
- a.contraction of eyeball
- b.expansion of eyeball
- c.dryness of optic nerve
- d.All are true
Answer: (B) expansion of eyeball
In myopia (short-sightedness) the eyeball is elongated from front to back, or the lens is too curved, so light from distant objects is focused in front of the retina; "expansion of eyeball" describes this lengthening. It is corrected with a concave (diverging) lens. In hypermetropia (long-sightedness) the eyeball is too short, the image forms behind the retina and a convex lens is used. Presbyopia is the age-related loss of accommodation (bifocal lens), astigmatism comes from an uneven cornea (cylindrical lens) and cataract is clouding of the lens. The optic nerve has nothing to do with myopia.