title: Radial Shape Discrimination in eyes at high risk of developing neovascular Age-Related Macular Degeneration
Creators: name: Pitrelli Vazquez, NM
Publisher: name: University of Liverpool Repository
Year: 2017

description: Aims The aim of this study was to investigate the use of a novel handheld Radial Shape Discrimination test (the hRSD test) in eyes at high risk of developing neovascular Age-Related Macular Degeneration (nAMD). The properties of the hRSD test that were investigated include the test-retest repeatability and the stability over time in clinically stable participants. The relationship between hRSD scores and other measurements of visual function (visual acuity, VA and contrast sensitivity, CS) were explored along with the relationship with retinal structural changes (foveal large drusen, ellipsoid zone disruption, EZD and central subfield thickness, CST). Methods A sample of 100 participants with unilateral nAMD was recruited from a UK ophthalmology clinic. The unaffected eye (the study eye, SE) had no evidence of nAMD, VA≤0.4 logMAR and was considered to be at risk of developing nAMD due to contralateral involvement. Participants performed the hRSD test on five consecutive visits, spread over approximately six months. All participants performed VA and Optical Coherence Tomography (OCT) at all visits. CS was measured in a subgroup of 34 participants. A usability questionnaire was completed at the last visit. Results The overall mean hRSD score in SEs was -0.56 ±0.16 (95%CI -0.60 to -0.53) logMAR for a group whose mean age was 77±7 years. Older participants had worse hRSD scores (r=0.37, p=0.0005) which corresponded to a deterioration of 0.08 logMAR per decade (slope of the linear regression). The test-retest repeatability over two consecutive visits revealed good agreement (bias=-0.004 logMAR, upper and lower limits of agreement: 0.27 and -0.28 logMAR). The coefficient of repeatability over five visits was 0.33 logMAR. There were no trends seen (no learning effects). The hRSD test was less repeatable than VA when compared by means of intraclass correlation coefficients (0.85 vs. 0.93). No correlation was seen between hRSD and VA (p=0.9) or CS (p=0.1). Of the three aspects of retinal structure investigated, only large drusen and EZD had a significant effect on hRSD scores (p=0.02 and p=0.01). Finally, the usability questionnaire revealed a very good acceptability of the test. Discussion The hRSD test has been suggested to be an effective mean of detecting nAMD. This study contributes to the ongoing assessment of the hRSD test in a key population with eyes at risk of nAMD. Understanding the performance of tests in the absence of disease progression is important to correctly interpret potential changes as clinically or non-clinically significant. Although the hRSD test was less repeatable than VA, the degree of variability can be considered acceptable in view of the large dynamic range seen between early and late AMD. The hRSD test has the advantage of being portable, capable of self-administration and well accepted by patients. The results from this study support the idea that the hRSD test is a better indicator of foveal integrity in the early stages of AMD compared to VA, as shown by the results of the correlations with structural parameters.