Vision tests for the home PC: Test validation and results from a lutein supplementation trial

Purpose: To allow frequent and calibrated vision testing of clinical trial subjects between periodic clinic visits. Methods: 14 PC-based vision measures were collected, including: "ETDRS" visual acuity, "Pelli-Robson" contrast sensitivity, and central visual field isoptersS at 3 light levels (full, 4%, and 0.1% luminance); low contrast acuityS; glare-impaired contrast sensitivity; macular pigment densityS; 48-hue discriminationS; and primary color half-saturation setting. All letter tests converged towards threshold using 2 interspersed PEST routines; PEST routines for each of 24, 12, and 12 directions were used in the visual field tests. Tests marked "S" self-adjusted to the subject's vision level during initial sessions; subsequent sessions were used to compute reproducibility. Home monitor screens were calibrated using a simple grayscale setting and an off-the-shelf luxmeter for luminance, and a dollar bill for pixel size. Between-sessions variability was used to compute 95% confidence intervals (CI.95). Normally sighted and visually impaired subjects were recruited to validate the tests, using their home PCs to collect weekly vision measures; RP patients used the tests as outcome measures during a clinical trial. Test results were compared to standard vison tests in 3-6 lab visits. Results: Subjects were able to perform all tests in a 75-min. session every week. PC-measured vision levels corresponded well with lab-measured levels. CI.95 were: VAfull, ±0.8 dB; VA4%, ±1.6 dB; VA0.1%, 3.4 dB; VALC, ±2.4 dB; CSfull, ±2.3 dB; CS4%, ±1.4 dB; CS0.1%, ±2.1 dB; CSglare, ±2.0 dB; VFfull, ±3.5 dB; VF4%, ±8.7 dB; VF0.1%, ±11.4 dB. Use of dual PESTs in VA and CS tests reduced CI.95 by 0-30%. Results in study patients correlated highly with lab-based measures. Conclusions: CI.95 values for most home PC tests are similar to published laboratory values, strongly supporting the validity of PC-based tests as longitudinal measures in clinical trials.