Powerful optical devices useful to persons with vision impairments that are not successfully corrected by the usual prescription lenses.

The transparent disc in the middle of the eye behind the pupil that brings rays of light into focus on the retina.

Visual acuity that does not exceed 20/200 in the better eye with correcting lens; field of vision no greater than 20 degrees in its widest angle (Visual acuity of 20/200

Surgical tool using an intense beam of light energy to close rips, make holes, destroy new vessels (photocoagulation), or to open channels as in the treatment of glaucoma.