Readability of approach charts as a function of visual acuity, luminance, and printing format.

This study determined the ability of 12 presbyopic subjects to read numerals from aeronautical approach procedure charts. The readability of chart numerals was determined for 15 size and contrast combinations as a function of near visual acuity (equivalent 20/20, 20/40, and 20/60) and chart brightness (100 and 1.0 ft L). Test subjects were evaluated at the normal near-visual-acuity level (20/20) and the minal near-visual-acuity levels (20/40) for Classes I and II and 20/60 for Class III) as specified in the FAA's Guide for Aviation Medical Examiners. The results indicated that subjects with 20/20 near visual acuity could read all chart numerals under bright and dim luminance conditions. Subjects with 20/40 and 20/60 levels of near visual acuity experienced reading difficulty under bright conditions and increased difficulty under dim luminance.