A simple model to predict the sensitivity to change of visual acuity measurements.

Background: Estimates of test-retest variability (TRV) in the form of a 95% range have been suggested as providing a cutoff value (or "change-criterion") against which measured acuity changes can be judged to decide whether they are indicative of a clinically important change. This approach is based on ensuring that the specificity of the procedure is 95% in individuals with no real change. In an earlier article we investigated empirically the ability of the procedure to detect varying degrees of change (its sensitivity).

The effect of optical defocus on the test-retest variability of visual acuity measurements.

Purpose: To determine the effect of optical defocus on the test-retest variability (TRV) of visual acuity measurements in normal subjects.

Methods: Normal subjects underwent repeated visual acuity measurement with optical defocus of 0, 0.50, and 1.

How sensitive to clinical change are ETDRS logMAR visual acuity measurements?

Purpose: To determine the sensitivity to change and specificity achieved when published test-retest variability (TRV) data are used to determine whether measured changes in ETDRS logarithm of the minimum angle of resolution (logMAR) visual acuity reflect true clinical change or are attributable to measurement error alone.

Methods: Various degrees of change in visual acuity were simulated in a group of normal subjects by adjusting test difficulty through manipulation of viewing distance. Sensitivity to simulated change and specificity were determined with change criteria derived from published Bland-Altman 95% ranges for TRV.