Intersession test—retest variability of conventional and novel parameters using the MP-1 microperimeter

Evan N Wong,1 David A Mackey,1 William H Morgan,1,2 Fred Kuanfu Chen1,2 1Centre for Ophthalmology and Visual Science, (Lions Eye Institute), The University of Western Australia, Perth, WA, Australia; 2Department of Ophthalmology, Royal Perth Hospital, Perth, WA, Australia Purpose: To investigate the intersession test–retest variability (TRV) of topography- and threshold-based parameters derived from the Nidek MP-1.Design: Prospective observational study.Methods: Sixteen participants with and without central scotoma underwent microperimetry in one eye over three sessions at 1-month intervals in a single institution. We calculated 95% coefficient of repeatability (CR) for the number of normal-suspect (NS) loci, relative scotoma (RS) and dense scotoma (DS), median macular sensitivity (MS), mean sensitivity of responding loci (RLS), perilesional loci (PLS), and extralesional loci (ELS). Topographical agreement score of mapping NS and DS loci (TASNS and TASDS) were also calculated for each patient.Results: Mean (range) age was 50 (21–86) years. The CR (95% confidence intervals) for NS, RS, and DS were 9.9 (6.5–13.3), 9.5 (6.2–12.7), and 3.0 (1.1–4.1) respectively. CR (95% CIs) for median MS, mean RLS, PLS, and ELS were 3.4 (2.3–4.5), 1.6 (1.1–2.2), 1.8 (0.9–2.6), and 2.8 (1.5–4.0) dB. We found significant change in thresholds between Test 1, and Tests 2 and 3 (both P=0.03), but not between Tests 2 and 3 (P=0.8). Medians (range) TASNS and TASDS were 74% (39%–100%) and 77% (0%–97%), respectively, between Tests 2 and 3.Conclusion: We recommend the use of four DS loci (upper limit of CR) as the limit of TRV for assessing change. There was large interindividual variability in NS or DS mapping agreement. We recommend discarding the first microperimetry test and caution the use of a change in spatial distribution to determine disease progression. Keywords: test–retest variability, TASNS, TASDS, Nidek MP-