N. Fontaine et al., Contrast and glare testing in the assessment of visual performance of candidate eyes for penetrating keratoplasty, CORNEA, 19(4), 2000, pp. 433-438
Purpose. To determine whether visual acuity (VA) measurements performed at
low levels of contrast and glare are a better diagnostic tool for determini
ng whether corneal clouding warrants surgery. Methods. Fifty-nine subjects
were recruited from among the candidates for corneal graft. Monocular VA wa
s measured with three Regan contrast VA charts: 96, 25, and 11%, with and w
ithout glare provided by the Brightness Acuity Tester (BAT). The discrimina
tive ability of the tests was estimated using the area (A(R)) under receive
r operating characteristic (ROC) curves. Associations between the different
VA tests and the Visual Function Index (VF-14) score were studied, using S
pearman coefficients. Results. When comparing candidate eyes with contralat
eral eyes with corneal disease, lower contrasts VA tests provided greater d
iscriminative power. VA measurements made with glare also tended to provide
greater discrimination. In fact, discrimination was best with 11% contrast
VA with glare, but "testability" was poor. The most practical test in a cl
inical setting, which retained high discriminative ability (0.798), was the
25% contrast VA with glare. The eye with the best VA correlated strongly w
ith the VF-14, especially at 25% contrast without glare, resulting in an R-
s of -0.729. Conclusion. Twenty-five percent contrast VA with BAT could hel
p the practitioner to decide whether a corneal transplant is warranted when
symptoms of reduced vision are more important than what high-contrast VA m
ight indicate.