Development and Validation of a Smartphone-based Contrast Sensitivity Test.

Esmael Habtamu,Matthew J Burton,Andrew Bastawrous,Zerihun Tadesse,Bizuayehu Gashaw,E Kelly Callahan,David Macleod,Nigel M Bolster

doi:10.1167/tvst.8.5.13

Abstract

PurposeContrast sensitivity (CS) testing is an important measure of visual function reflecting variations in everyday visual experience in different conditions and helps to identify more subtle vision loss. However, it is only infrequently used. To make this more accessible, we have developed and validated a smartphone-based CS test.MethodsA new tumbling-E smartphone-based CS test was developed, Peek Contrast Sensitivity (PeekCS). This was field tested and refined through several iterations. Reference standard was a tumbling-E Pelli-Robson CS test (PRCS). The validation study was conducted in community clinics in Ethiopia. Test-retest variability was measured for both PRCS and PeekCS. PRCS and PeekCS were then compared. Correlation coefficients and 95% confidence intervals (CIs) were calculated; 95% limits of agreement were calculated and displayed on Bland-Altman plots.ResultsPeekCS showed strong repeatability (correlation coefficient: 0.93; 95% CI: 0.91–0.95), which was comparable with PRCS (correlation coefficient: 0.96; 95% CI: 0.95–0.97). The 95% limit of agreement for test-retest variability of PRCS and PeekCS were −0.20 to 0.21 and −0.31 to 0.29, respectively. PRCS and PeekCS were highly correlated: 0.94 (95% CI: 0.93–0.95); 95% limits of agreement −0.27 to 0.29; and mean difference 0.010 (95% CI: −0.001 to 0.022). PeekCS had a faster testing time (44.6 seconds) than PRCS (48.6 seconds): mean difference −3.98 (95% CI: −5.38 to −2.58); P < 0.001.ConclusionsThe smartphone-based PeekCS is a repeatable and rapid test, providing results that are highly comparable with the commonly used PRCS test.Translational RelevancePeekCS provides an accessible and easy to perform alternative for CS testing, particularly in the community setting.

Highlights

Visual acuity (VA) is the most frequently performed measure of visual function
Peek Contrast Sensitivity (PeekCS) showed strong repeatability, which was comparable with Pelli-Robson CS test (PRCS)
PRCS and PeekCS were highly correlated: 0.94; 95% limits of agreement À0.27 to 0.29; and mean difference 0.010

Summary

Introduction

Visual acuity (VA) is the most frequently performed measure of visual function. In a VA test, optotypes of decreasing size with a fixed high contrast level are presented. Contrast sensitivity (CS), an important measure of visual function, is the ability to detect a difference between the luminance of an object and its background.[1,2] The varying levels of contrast presented in a CS test more accurately represent variations common to everyday visual experience.[3,4]. Owing to the finite combinations of optotype and background grays, it is not possible to have an exact alignment between the contrast sensitivities tested with PeekCS and the Pelli-Robson charts. The difference between the two tests is never more than two-thirds of the difference between score stages (i.e., 0.10 log units). This study was nested within a previously reported randomized placebo controlled trial of oral doxycycline for the prevention of postoperative trichiasis.[26]

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Conclusion