Table 2.

Mean (SD) a-wave amplitudes for rod and cone responses grouped by risk alleles

Background (rod or cone system)	Flash strength, photopic cd⋅m−2⋅s	Mean (SD) amplitudes, µV			P value (mixed model)
		No risk alleles (group 0), n = 37	One risk allele (group 1), n = 101	Two risk alleles (group 2), n = 48
Rod-saturating blue background (CONE-DRIVEN RESPONSES)	0.67	17.2 (5.2)	16.0 (4.3)	14.9 (4.3)	0.152
	4.0	33.8 (8.9)	31.7 (7.3)	28.9 (7.5)	0.029*
	13	45.1 (10.1)	42.2 (8.6)	39 (8.4)	0.023*
	67	56.0 (13.0)	51.3 (11.3)	47.5 (9.8)	0.003*
Estimated ROD RESPONSES	0.67	77.6 (29.2)	74.9 (21.5)	68.6 (25.5)	0.574
	4.0	121.1 (31.9)	118.4 (26.9)	111.0 (28.4)	0.378
	13	125.7 (33.4)	123.8 (26.6)	115.7 (30.2)	0.355
	67	147.5 (36)	145.7 (29.1)	136.6 (30.8)	0.957

P values in the final column are from the mixed linear model. Responses on the blue background are from the cone system alone; here, all comparisons are significant except the dimmest flash. Subtraction of these responses from those to identical flashes delivered in the dark yields an estimate of the rod response; none of the comparisons were significant. As the blue background is still likely to mildly desensitize the cones, the subtraction might not be complete, and any residual trend in the rod response amplitudes might still be attributable to residual cone system components. The b-wave comparisons were not significant. Averaged responses are shown in Fig. 2 (except the dimmest flash). Comparisons for responses in the dark (Fig. 2 A–C) were not significant. *P < 0.05.