Performance, usability and comparison of two versions of a new macular vision test: the handheld Radial Shape Discrimination test

Abstract

BackgroundCentral vision, critical for everyday tasks such as reading and driving, is impacted by age-related changes in the eye and by diseases such as age-related macular degeneration. The detection of changes in macular function is therefore important. The Radial Shape Discrimination (RSD) test measures the threshold at which distortions in a radial frequency pattern can be detected and there is evidence that it is more sensitive to macular pathology than visual acuity (VA). It also provides a more quantitative measure of macular function than the commonly available Amsler grid. Recently, handheld versions of the test (hRSD) in which stimuli are presented on mobile devices (e.g., Apple iPod Touch, iPhone) have been developed. We investigated the characteristics of the hRSD test in healthy participants.MethodsData were collected using both three-alternative forced choice (3AFC) and 4AFC versions of the hRSD test, presented on an Apple iPod Touch. For the 3AFC version, data from a single test session were available for 186 (72 male; mean ± SD age 42 ± 17y; range 16–90y) healthy participants. Test-retest data were available for subgroups of participants (intra-session: N = 74; tests approximately 2 months apart: N = 30; tests 39 months apart: N = 15). The 3AFC and 4AFC versions were directly compared in 106 participants who also completed a usability questionnaire. Distance and near VA and Pelli Robson Contrast Sensitivity (CS) data were collected and undilated fundoscopy performed on the majority of participants.ResultsMean (±SD) 3AFC hRSD threshold was −0.77 ± 0.14 logMAR, and was statistically significantly correlated with age (Pearson r = 0.35; p < 0.001). The linear regression of hRSD threshold on age had a slope of +0.0026 compared to +0.0051 for near VA (which also correlated with age: r = 0.51; p < 0.001). There were no statistically significant differences in hRSD thresholds for any of the test-retest subgroups. We also observed no statistically significant difference between 3AFC (−0.82 ± 0.11 logMAR) and 4AFC (−0.80 ± 0.12 logMAR) hRSD thresholds (t = 1.85, p = 0.067) and participants reported excellent test usability with no strong preference expressed between the 3AFC and 4AFC versions of the test.DiscussionThe 3AFC hRSD thresholds we report are consistent with a number of previous studies, as is its greater stability in ageing compared to VA. We have also shown that in the absence of pathology, thresholds are stable over short and long timescales. The 4AFC thresholds we have reported provide a baseline for future investigations, and we have confirmed that 3AFC and 4AFC thresholds are similar, providing a basis of comparisons between studies using the different versions. As the hRSD test is easy to use and relatively inexpensive, clinical studies are now required to establish its ability to detect and monitor macular pathologies.

Radial shape discrimination testing for new-onset neovascular age-related macular degeneration in at-risk eyes

“…This indicated statistically significant differences between the FE and both SE results (SE non-converters p<0.001; SE converters p = 0.017); the difference between the SE of converters and non-converters did not reach statistical significance (p = 0.065). For comparison, we also extracted data for a group of healthy eyes we have previously published[ 18 ]. The mean hRSD threshold calculated for one randomly selected eye from fifty-six healthy participants (mean age 63±11y), tested with the same 3AFC version of hRSD test as used in the present study, was -0.71±0.16logMAR.…”

“…It has been shown previously that hRSD test results are stable and repeatable in healthy eyes[ 18 ], are affected by the development of macular disease, and are related to disease severity[ 17 ]. We used a prospective, longitudinal, observational study design similar to that of Do et al (2012)[ 22 ] and followed the disease-free eyes of patients being treated for unilateral nAMD.…”

“…Because of the sensitivity of the human visual system to these distortions, RSD thresholds fall into the hyperacuity range. While RSD threshold reaches maturity later than resolution acuity, once adult thresholds are reached they remain stable in the absence of pathology, and are relatively resistant to normal healthy ageing compared to VA[ 16 , 18 ]. The development of AMD has been demonstrated to increase RSD thresholds [ 15 ] and test performance has been shown to be related to the severity of macular disease[ 17 ].…”

Multi-line Adaptive Perimetry (MAP): A New Procedure for Quantifying Visual Field Integrity for Rapid Assessment of Macular Diseases

“…Since the degree of perceptual disturbance associated with MD naturally tends to mirror the progression of underlying disease status (i.e., retinal disarray or photoreceptor loss), a fine-grained quantitative assessment of visual field integrity could provide an effective means for tracking MD symptomology to allow earlier intervention, for example, by detecting sudden onset of CNV to immediately refer patients to the clinic, or by monitoring posttreatment remediation of visual function. Recent computerized assessments, such as the Reichter Foresee preferential hyperacuity perimetry (PHP), 12 the Foresee HOME, 13 the Radial Shape Discrimination test (RSD), 14 and the D-chart, 15 aim to localize and quantify visual field defects using patient responses to carefully controlled visual stimuli and specialized scoring algorithms. For example, PHP presents a horizontal or vertical dotted line in which a subset of elements is slightly misaligned in the shape of a small Gaussian “bump.” The patient is instructed to indicate the location of the distorted region on each trial, and MD patients with pathological distortion will often indicate erroneous locations on the straight part of the line that appear more distorted than the actual target bump.…”

Test-Retest-Reliability of Computer-Based Metamorphopsia Measurement in Macular Diseases

“…Zudem ist die Vergleichbarkeit von Tests eingeschränkt, die sich in der Größe des untersuchten Gesichtsfeldes unterscheiden. Ku et al [34] untersuchten die Test-Retest-Reliabilität des Tests myVisionTrack, der die zentralen 3°des Gesichtsfeldes abdeckt und fanden keinen statistisch signifikanten Unterschied zwischen den beiden Messungen. M-CHARTS prüfen Metamorphopsien innerhalb von maximal 10°im horizontalen oder vertikalen Meridian.…”