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Noelia Pitrelli Vazquez, Simon P Harding, Heinrich Heimann, Paul C Knox; Stability of performance of a handheld radial shape discrimination test in patients at risk of developing neovascular AMD.. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):2220.
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© ARVO (1962-2015); The Authors (2016-present)
We are currently investigating a handheld Radial Shape Discrimination (hRSD) test (Wang et al, 2013, IOVS 54:5497) as a potential screening test for detecting new neovascular age-related macular degeneration (nvAMD). The stability of performance of the hRSD test over time was assessed in patients at risk of developing nvAMD prior to disease development.
Thirty-three non-diabetic participants (mean±SD age: 77±7 years; range: 60-91 years, 19 female) were recruited from a UK AMD clinic. Participants had nvAMD in one eye (for which they were receiving treatment) and no evidence of nvAMD in their fellow eye (study eye, SE) with a visual acuity of 0.4 logMAR or better in that eye. They performed the hRSD test with the SE, under supervision, on 5 occasions over a period of 5.5±0.8 months. Presence or absence of large drusen (maximum vertical diameter >70µm) and disruption of the ellipsoid zone (EZ) within 1500µm of the foveal centre were assessed on Heidelberg Spectralis OCT at baseline.
Group mean (±SD) hRSD thresholds at each time point were -0.54±0.18, -0.57±0.17, -0.56±0.17, -0.56±0.18 and -0.59±0.22 logMAR. A repeated measures ANOVA demonstrated that these thresholds were not statistically significantly different [F(4, 116)=0.56, p=0.694]. Regression analysis of threshold over time showed that the mean slope of individual regression lines was -0.000252±0.001206. The mean (95%CI) difference in hRSD threshold between the first and the last time points was -0.05 (-0.13 to 0.03) logMAR. Presence/absence of large drusen, or disruption to the EZ had no statistically significant effect on hRSD test performance (p=0.10 and p=0.23 respectively).
Stability over time prior to the development of the target pathology is an important aspect of a diagnostic test. We have confirmed that hRSD test performance was stable over a period of approximately six months in the fellow (non-nvAMD) eyes of AMD patients and that it remained consistently below the cut-off value for the hRSD test previously suggested to be indicative of disease (-0.37 logMAR).
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