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F. K. Chen, P. J. Patel, W. Xing, C. Bunce, C. Egan, A. Tufail, P. J. Coffey, G. S. Rubin, L. Da Cruz; Reliability of Nidek MP1 in Fixation Test and Retinal Sensitivity Measurement in Patients With Macular Disease. Invest. Ophthalmol. Vis. Sci. 2009;50(13):3733.
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© ARVO (1962-2015); The Authors (2016-present)
To determine the reliability of using Nidek MP1 for fixation and retinal sensitivity measurements in patients with macular disease.
In this prospective study, 50 patients with various macular diseases were enrolled. 1 examiner performed 2 identical consecutive tests (30 sec fixation task then 10-2 grid microperimetry task) for all patients. Kappa values for fixation stability classification (FSC) were calculated for the fixation and microperimetry tasks (FxT and MpT) separately as well as between the 2 methods. Fixation centroid separation between the 2 FxTs was derived from differential map using automated image registration if possible. Test-retest variability for mean sensitivity (MS), mean deviation (MD), point-wise sensitivity (PWS), local defect classification (LDC), average sensitivity for the central macula (CMS, 16 loci inside 5º radius), paracentral macular sensitivity (PMS, 52 loci in the 5-10º ring), and dense scotoma size (DSS) were analyzed by calculating the 95% coefficients of repeatability or percentage agreement.
Mean (SD) age and visual acuity were 61 (15) years and 0.34 (0.32) logMAR, respectively. 92% and 70% of patients (kappa: 0.68 and 0.53) had perfect agreement in FSC for FxT and MpT, respectively. Agreement between FSCs derived from FxT and MpT was 44 - 50% (kappa: 0.06 - 0.17). Median centroid separation was 0.3º (range: 0.1 to 8.6º) between the 2 FxTs. 74% of patients had fixation centroid separation by up to 0.4º between the 2 FxTs. For microperimetry, the mean difference in MS between tests 1 and 2 was +0.2 dB (SD, 0.9 dB; p = 0.127). The coefficients of repeatability for MS, MD, CMS, PMS and DSS were 1.81, 2.56, 2.13, 1.93 dB, and 8 test loci respectively. The mean (SD) of coefficients of repeatability for PWS across all 68 loci was 5.56 (0.86) dB. 76% of all test loci in all patients had perfect agreement in LDC.
FSC derived from FxT has poor agreement with FSC derived from MpT. FSC results derived from 2 separate FxTs has good agreement. Test-retest variability is lowest for MS and highest for PWS. However, MS does not provide spatial information. We recommend the use of CMS and PMS for monitoring macular function and consider a change of greater than 2.56 and 2.31 dB (the upper limit of the 95% CI of their coefficients of repeatability), respectively, to exceed test-retest variability.
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