One eye is a necessity; two eyes are a luxury: a commentary.
D000368:Aged; D002387:Cataract Extraction / Q000592:standards*; D006801:Humans; D007910:Lenses, Intraocular; D008297:Male; D006278:Medicare; D014481:United States; D014787:Vision Tests / Q000592:standards*; D014792:Visual Acuity