It is desirable to standardize the conditions under which visual acuity is measured because of its importance in determining whether subjects meet occupational vision standards and as an indicator of the extent or stability of pathological conditions. The chart luminance is one parameter which needs to be standardized, and the effect of the luminance level upon acuity measurement is a critical factor in this determination. These data are measured for a subject population using Landolt rings and British letters. Over a “normal” photopic range of 40 to 600 cd/m2 the relation between the logarithm of the minimum angle of resolution (log MAR)) and log L (luminance) can be approximated by a straight line. A doubling of the luminance level within this range improves the acuity measurement by approximately one letter on a five-letter row. Landolt ring acuities are less affected by luminance than letter acuities. The application of these results to establishing a standardized luminance level and tolerance range is discussed.
Presented at the annual meeting of the American Academy of Optometry, Houston, Texas, 1983.
Received February 8, 1984; revision received June 13, 1984.
*Optometrist, Ph.D., Member of Faculty, F.A.A.O.
†Optometrist, M.S., Member of Faculty, F.A.A.O.
‡Optometrist, Member of Faculty, F.A.A.O.
James E. Sheedy
University of California, Berkeley
School of Optometry
Berkeley, California 94720
© 1984 American Academy of Optometry