Question

name one defect of vision which cannot be corrected by any type of spectacle lenses?....is it blindness? what is range of vision?

Answer 1

Following are the eye diseases that cannot be corrected by using lens:
1. Cataract-opaqueness of eye lens[causes temporary blindness]
2. Glaucoma-increase of pressure of vitreous humour of eye- may lead to temporary blindness
3. Retinopathy[destruction of retina- may cause permanent blindness]

Answer 2

1. Retinopathy: Destruction of retina (may cause permanent blindness if delayed) 

2. Cataract: Opaqueness of eye lens (temporary blindness but not permanent blindness) 

3. Glaucoma: Increased of pressure of vitreous humor of eye (may cause permanent blindness if delayed)