There are three classification systems for individuals with visual impairment that are used by education professionals. To be declared legally blind, an individual must have visual acuity of 20/200 or less, or have a field of vision restricted to 20 degrees or less at the widest point. However, this federal classification system is used primarily to determine eligibility for adult agency services.
have an eye for something. to be good at noticing a particular type of thing She has an eye for detail. He had an eye for the unusual and the exotic which made him a very good shopping companion. See also: an, eye, for, have.
When  an eye for an Eye was written it was meant to keep someone from , say, killing you because you maimed or injured their sheep. It was not literal. It was the basis of reasonable recompense for loss or damage. Pay for the sheep. However, capital offense of actually murdering someone was met with the the full punishment available, which was death.