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Yi-Zhong Wang, Yu-Guang He, Gina Mitzel, Song Zhang, Michael B. Bartlett; Handheld Shape Discrimination Hyperacuity (hSDH) Test on a Mobile Device for Remote Monitoring of Visual Function in Maculopathy. Invest. Ophthalmol. Vis. Sci. 2012;53(14):2914.
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Recent advances in treatments for age-related macular degeneration (AMD) and diabetic retinopathy (DR) suggest that frequent monitoring of disease condition is crucial for timely intervention. Here we evaluated a new handheld shape discrimination hyperacuity (hSDH) test iPhone app designed for visual function self-monitoring in patients with maculopathy.
One hundred eyes from 100 subjects (27 age-matched normal control; 37 AMD; and 36 DR) were included on the basis of clinical and SD-OCT documentation and VA 20/100 or better. The hSDH test was implemented on the iPhone/iPod Touch platform using a spatial 3-alternative forced-choice (3AFC) staircase paradigm. Visual stimuli in each trial included 3 circular shapes: 1 distorted and 2 undistorted. The task was to indicate by touch input which of 3 shapes was distorted. A maximum likelihood fitting procedure was used to estimate hSDH for detecting distortion. A cross-sectional study was conducted to compare the hSDH test with a previously established desktop PC-based SDH testing protocol and to assess the effect of disease severity on hSDH. In addition, a 6-month pilot longitudinal study was conducted with 46 patients (9 AMD, 37 DR) who were asked to take hSDH test at least once a week at home.
The hSDH results obtained with the iPod Touch testing protocol were highly correlated with those obtained with the desktop testing protocol (r=0.88, p<0.0001), and Bland-Altman analysis indicated no significant difference in SDH measurements obtained with these two testing protocols. One-way ANOVA analyses indicated that the mean hSDH of the eyes with advanced AMD (n=16) or with severe to very severe non-proliferative DR (NPDR) (n=12) was significantly worse than that of the eyes with high-risk early AMD (n=11) or with mild-to-moderate NPDR (n=11), respectively (p<0.0001). During the 6-month study, the average weekly compliance rate of the patients who completed the study (n=36) was 0.84±0.20SD, and the average number of tests taken was 1.7±1.2SD per week. For the eyes with no clinically significant change of disease condition over 6 months (n=30), the average standard deviation of hSDH measurements was 0.10 logMAR±0.028SD.
This feasibility study demonstrated that hSDH test on a mobile device is comparable to PC-based testing method. As a mobile app, it is intuitive to use, low-cost, and readily accessible. The results also suggested that hSDH test is sensitive to the severity of maculopathy, and has the potential to provide patients with maculopathy a new tool to monitor their visual function outside of the clinical setting.
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