Amplitude and implicit time of the OP wavelets were examined as a function of flash intensity at all ages. Responses to two intensities were selected for further statistical analyses. The more intense flash produced approximately 17,000 R*, a stimulus sufficient to saturate the rod dominated a-wave and to evoke a b-wave driven by rod and cone activity.
51 The less intense flash produced approximately 65 R*, sufficient to saturate the rod-driven b-wave but too dim to evoke a cone-driven b-wave.
51
For normal rats, OP amplitude and implicit time were each evaluated by repeated-measures analysis of variance (ANOVA); the factors were OP number (OP2, OP3, OP4, OP5), age (P18, P31, P47, P67), and flash intensity (17,000 R*, 65 R*). OP interpeak interval was evaluated by an additional repeated-measures ANOVA with factors interpeak interval (OP2–3, OP3–4, OP4–5), age, and flash intensity. OP amplitudes of the P31 group of ROP rats were compared with those of the P31 normal rats using a three-factor (group, OP number, flash intensity) ANOVA. A complete data set is required to perform repeated-measures ANOVA. In 24 of 384 instances, an OP wavelet was not detectable; to fill these cells, a random amplitude value within the range for that condition was entered, and the implicit time was interpolated or extrapolated by linear fit to that animal’s observed OPs. The significance level for all tests was P < 0.01.