Contrast and glare testing in the assessment of visual performance of candidate eyes for penetrating keratoplasty

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.