Is my mother considered blind?
with 20/80 visual acuity in one eye your mother is neither blind, nor "legally blind", regardless of the condition of the other eye. To be considered legally blind, best visual acuity in your best eye has to be 20/200. 20/80 means that your mother has to stand 20 feet from an object to see it that the person with full sight could see from 80 feet.
The term "balance" in the other eye refers to an eyeglass prescription; if no prescription will improves the vision in that eye, there is no reason to incur the cost of a precise prescription lens; in that case the optician is requested to so that the two lenses are "balanced", to allow the glasses will sit straight. the term "NIL" means none or nothing, ie. no improvement of vision in that eye.
