LogMAR

A standardised scale for measuring visual acuity based on the logarithm (base 10) of the minimum angle of resolution, used in the Bailey-Lovie eye chart and widely adopted in clinical vision research. A logMAR value of 0.0 corresponds to 20/20 (6/6) vision, with higher values indicating worse acuity (e.g., 1.0 = 20/200, the US legal blindness threshold). The logMAR scale is preferred over the Snellen fraction in research and clinical trials because it provides uniform steps on a logarithmic scale, consistent letter sizing and spacing, and equal legibility across rows — properties that enable valid statistical analysis of visual acuity data. In accessibility research, logMAR measurements are used to quantify visual performance when evaluating assistive technologies, display modifications, and interface designs for users with low vision.