Corrected distance visual acuity (CDVA / BCVA)

Method

Distance visual acuity on a logMAR chart (ETDRS or equivalent) measured after subjective refraction to the patient's optimal spectacle or contact lens prescription, at the chart's stated test distance and luminance.

The method is part of the endpoint identity. Studies measuring the same quantity by a different method are held as separate endpoints.

Notes

CRITICAL SIGN INVERSION against Snellen or decimal acuity, which measure the same construct on the same charts in the same patients but IMPROVE BY RISING while logMAR improves by falling. A logMAR change of -0.09 is a gain of roughly 4.5 letters, about one line; converted carelessly it becomes a loss. Never accept an acuity value without its scale. The second near-miss is acuity read in the eye's native refractive state, its own node: taken minutes apart on the same chart in the same unit, and in keratoconus the two dissociate strongly because refraction masks the irregular astigmatism the intervention targets.