How can you bcome blind? by using to much computer? staring at a light?

Answer 1

No, and no, though lasers above a certain power can be dangerous, if looked at..

The top reason for becoming blind before the age of 65 in the UK and USA is diabetes.
(followed, probably, by glaucoma and accidents, principally motor vehicle)
Macular degeneration is the top blinding condition at older ages.

Elsewhere conditions like trachoma and onchocerciasis may offer greater risk in the younger age group, but world-wide the greatest cause of blindness is cataract: utterly treatable, but untreated due to poverty and the lack of medical resources.