The mean photopic, mesopic, and scotopic MS in dB (range; ±SD) in affected individuals was, respectively, 20.2 (range = 6.3–29.5, SD = ±6.5), 16.2 (range = 3.7–23.1, SD = ±5.3), and 1.3 (range = 0–13.3, SD = ±3.8) in the right eyes, and 21.1 (range = 9.8–28.9, SD = ±6.1), 16.8 (range = 9.6–23.5, SD = ±4.0), and 1.1 (range = 0–12.4, SD = ±3.5) in the left eyes; all were significantly different to the controls (P < 0.0001 in both eyes; unpaired t-test). The corresponding values in the control right eyes were 31.5 (range = 30.9–32.1, SD = ±1.7), 27.8 (range = 27.8–27.8, SD = ±0.2), and 16.7 dB (range = 15.7–17.8, SD = ±1.4). There was a high interocular correlation (Pearson correlation coefficient) in photopic (r = 0.96, P < 0.0001), mesopic (r = 0.9, P < 0.0001), and scotopic (r = 0.98, P < 0.0001).
An outlier was identified in a ROUT test (Q < 1%), subject 01–041, who has the hypomorphic allele M285R. He was not excluded from this analysis as we provided sufficient evidence in a separate study that this represents part of the
KCNV2 disease spectrum.
15 The MS in the right and left eyes were, respectively, 29.6 and 28.9 dB in photopic, 23.2 and 22.2 dB in mesopic, and 13.4 and 12.4 dB in scotopic testing. This was nominally much higher than the average in affected individuals and comparable to the healthy controls, particularly under photopic conditions (
Fig. 3). Similarly, he was the patient that had the highest MS in the scotopic testing and the only affected individual with no floor effects in any position in the grid.
Mesopic microperimetry in the CMZ versus PMZ were then analyzed. In the healthy controls, the mean MS (±SD; range) was 28.1 dB (SD = ±2, range = 25–34) and 27.6 dB (SD = ±2, range = 23–32) in the CMZ and PMZ, respectively. In affected individuals, the mean MS was 13.4 dB (range = 0–25, SD = ±9.2) in the CMZ and 18.1 (range = 0–3, SD = ±11.1) in the PMZ, which was statistically different to the healthy controls (P < 0.0001; unpaired t-test).
The noFs was also investigated. Similarly, given the high correlation, only values for the right eyes are subsequently described. The mean noF (±SD; range) was 4.6 (SD = ±5.3, range = 0–16) in photopic, 5 (SD = ±5.4, range = 0–15) in mesopic, and 23.2 (SD = ±8.6, range = 0–28) in scotopic conditions. Subject 01-041 was the only affected individual in which no floor effect was found. A simple linear regression model revealed an inverse relationship between age and MS, and a direct relationship between age and noF (
Fig. 4). A summary of the microperimetry data described herein is found in
Table 2.