Evaluation of a rapid test of dark adaptation

Abstract

Classical dark adaptation (DA) testing is a cumbersome and lengthy (45 min) procedure. We evaluated a newly described, rapid test (2 and a serum vA value < 40 /µg/100 ml). The times taken to complete the rapid test correlated well with rod-cone break times (r = 0.79, p < 0.001) and the final DA threshold (r = 0.71, p < 0.001) derived from classical DA curves. Serum vA levels were found to correlate with rapid test time, rod-cone break time, and final DA threshold according to logarithmic regression models (p < 0.002). In healthy controls, the mean ± SD time taken for the rapid test was 4.41 ± 0.83 min.; in vA-sufficient patients 4.59 ± 0.97 versus 7.63 ± 1.79 min in vA-deficient patients (p < 0.001). The rapid test was found to be reproducible over a 2-wk period. Seven vA-deficient patients were treated orally with 10,000 /µg vA daily for 4 wk and showed a mean improvement of 1.54 min in rapid test time (p < 0.005), 1.60 min in rod-cone break time (p < 0.001), and 0.2 log candela/m² in final DA threshold (p < 0.001). The sensitivity of the rapid test (at 1.5 SD) was 95%, while the specificity was 91%. Thus, the described rapid DA test correlates well with classical DA parameters and is suitable for evaluation under field conditions as a screening test for hypovitaminosis A.