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Mohamed A. Genead, Serena Salvatore, J. Jason McAnany, Gerald A. Fishman; Intrasession and Intersession Repeatability of Retinal Sensitivity Using a Modified Nidek MP-1 Microperimeter in Patients with Stargardt Disease. Invest. Ophthalmol. Vis. Sci. 2012;53(14):4370.
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To determine the intrasession/intersession repeatability of the MP-1 microperimeter in patients with Stargardt disease.
Nine patients with Stargardt disease were enrolled in the study. All patients underwent a complete ocular examination. Microperimetry was performed using the MP-1 microperimeter under both mesopic and scotopic test conditions three times for each patient (baseline "T1", after 30 minutes "T2", and after 1 week "T3"). To test scotopic retinal function, the instrument was modified by adding a 2 log unit neutral density filter and a 500 nm short-pass filter within the optical path. Retinal mean sensitivity (MS) of all tested points within a 37-loci grid centered on the fovea covering the central 140 of the macula and fixation stability, quantified as the bivariate contour ellipse area (BCEA), were examined.
The mean age of the patients was 33.1 (SD, 9.9) years. They had a mean visual acuity of 0.41 (SD, 0.39) log MAR and the disease-causing mutations in the ABCA4 gene were identified in all but one patient. The mean difference in MS between mesopic T1 and T2 was -0.89 dB (SD, 1.01 dB), whereas the mean difference in MS between scotopic T1 and T2 was -1.73 dB (SD, 0.99 dB). Both of these differences were statistically significant (p < 0.05). The mean MS values for T1 and T2 were averaged and compared to the value obtained for T3. Under the mesopic condition, the MS value at T3 was 1.49 dB (SD, 0.61 dB) less than the average sensitivity of T1 and T2 (t = 7.36, p < 0.01). In comparison, under the scotopic condition, the MS value at T3 was only 0.54 dB (SD, 0.94 dB) less than the average of T1 and T2 (t = 1.74, p = 0.12). The mean BCEA values under the mesopic condition were 9.52 deg2 and 7.32 deg2 for T1 and T2, respectively (t = 1.94, p = 0.09). The mean BCEA values under the scotopic condition were 15.41 deg2 and 12.43 deg2 for T1 and T2, respectively (t = -0.24, p = 0.82). The coefficient of repeatability for T1 and T2 for the BCEA was 7.78 deg2 and 26.20 deg2 under the mesopic and scotopic conditions, respectively. Under the mesopic and scotopic conditions, the BCEA values at T3 were 0.67 dB (SD, 6.80 dB) and 0.53 dB (SD, 8.65 dB) less than the average of T1 and T2, respectively (both p > 0.77).
Although statistically significant, the differences in MS between the tests were less than 2 dB under both the mesopic and scotopic conditions and small, non-statistically significant, differences were observed in fixation stability. These findings document a relatively narrow range of intrasession/intersession repeatability using the MP-1 and validate its use for monitoring the natural history of functional loss in Stargardt patients as well as their response to treatment.
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