A unit of measurement used by eye doctors and opticians to
communicate the degree of refractive error with respect to
nearsightedness, farsightedness and astigmatism. A +1-2.00
diopter reading indicates a mild form of refractive error. A
+1-6.00 on the diopter scale indicates a moderate to severe
condition, depending on the nature of the refractive
problem. Readings can go as high as +1-10.00 or more,
indicating very severe conditions.