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Fred Chen, Ian Constable, Evan Wong; A comparison of microperimetry parameters derived from the CenterVue MAIA and Nidek MP1S instruments in subjects with type 2 idiopathic macular telangiectasia (MacTel). Invest. Ophthalmol. Vis. Sci. 2013;54(15):3605.
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© ARVO (1962-2015); The Authors (2016-present)
To compare the retinal sensitivity and fixation stability measurements derived from 2 microperimeters in a cohort of subjects with MacTel.
In this prospective study, 13 patients with MacTel were enrolled. Mean acuity (SD) of the study eye was 74 (11) ETDRS letters. Using the same testing strategy (37 loci in central 6 degrees, 4-2 step, 200 ms), one eye of each patient was tested on two microperimetry devices in a randomized order in each session, for 3 sessions separated by 1 month apart. The difference in mean retinal sensitivity (MRS), temporal-wedge sensitivity (TWS), central-point sensitivity (CPS) and fixation stability (logBCEA) between the devices was analyzed by Bland-Altman plots and 95% limits of agreement (LOA).
Mean (SD) age was 60 (10) years. The average (SD) MRS derived from the MAIA and MP1S, for 13 subjects, over 3 visits, were 22.8 (4.3) and 14.0 (4.0) dB, respectively. The mean difference (95% LOA) was 8.8 dB (5.1 - 12.5) dB (p<0.001, paired t-test). Similarly, the average (SD) CPS derived from the MAIA and MP1S were 22.0 (3.6) and 13.1(4.9) dB, respectively. The mean difference (95% LOA) was 8.9 (3.5 - 14.3) dB (p<0.001, paired t-test). For the temporal wedge, the difference was smaller; 6.4 (-3.7 to 16.5) dB. This was driven by floor effects where some subjects had a dense scotoma in the temporal wedge resulting in a mean temporal wedge sensitivity of 0 on the MP1S. The average duration of microperimetry test for MAIA was 5’22’’, 5’15’’ and 5’09’’ for visits 1 to 3 respectively. For the MP1S, the duration of testing was 6’18’’, 7’14’’ and 6’35’’ for the 3 visits. Fixation stability in logBCEA (SD) at the final visit was 0.57 (0.28) and -0.08 (0.43) for MAIA and MP1S respectively (p<0.001). The mean difference for logBCEA (95% LOA) was 0.65 (0.02-1.29).
A small 37 loci grid microperimetry can be completed within 7 minutes per eye in MacTel subjects. Despite the same background luminance, MAIA and MP1S have different dynamic range of test locus luminance; 20 dB for the MP1S and 36 dB for the MAIA. Based on the differences in dynamic range and the luminance of the brightest stimulus, the expected discrepancy between the 2 microperimeters for retinal sensitivity should be 4 dB, much lower than the observed 9 dB difference.
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