Figure 2.

Examples of dark adaptation at two loci from an 89-year-old SDD participant with BCVA = 20/32. Curves are the fit of Equation A1 (Appendix) to the dark adaptation data. Rod intercept time (RIT) was defined as the time to detect a criterion stimulus of −3.1 log photopic cd/m² (dotted line); at the 12° locus = 17.1 minutes. Dark adaptation occurred at the 4° locus but the threshold at this retinal location never reached criterion, and no RIT could be derived.