A National Research Council study of visual disorders provided the mathematical formula
for the calculator. The formula gives equal weight to VA and VF, and combines the
person’s VA and VF to compute an overall measure of visual impairment. The common
logarithm (log) of the minimum angle of resolution (MAR), called the logMAR, plus
the absolute value of the MD divided by 22 (logMAR + |MD|/22) equals the overall measure
of the person’s visual impairment. Each eye is calculated separately. When the values
computed by the calculator equal or exceed 1.0 in both eyes, the visual disorder medically
equals the listing.
REFERENCE: National Research Council. (2002). Visual Impairments: Determining Eligibility for Social Security Benefits. Committee on Disability Determination for Individuals with Visual Impairments. Lennie,
P., and Van Hemel, S. B. (Eds.). Division of Behavioral and Social Sciences and Education.
Washington, D.C.: National Academy Press.