Validation of the Affordable, Portable International Visionkeys System for Visual Acuity and Stereopsis

Background: A new, portable computerized distance vision testing (screen plus remote) system called VisionKeys has been developed by the missions equipment developer EyeMobil so we validated it compared to conventional research testing devices.

Methods: Using a standardized protocol of surround HOTV optotype presentation, the VisionKeys was compared to M&S for patched monocular distance visual acuity. A different VisionKeys function with anaglyph spectacle distance stereopsis was compared to near stereo on Titmus circles with Polaroid goggles and PDI Check on an autostereoscopic screen. Raw scores were converted to logarithm and compared with non-parametric and Bland Altman tests.

Results: We recruited 145 ethnically diverse patients with range of acuity -0.4 to 2.6 (NLP) logMAR from a pediatric eye and adult strabismus practice showing median logMAR acuity of 0.0 with VisionKeys significantly finer resolution than 0.1 for M&S (Mann-Whitney z=2.6, p=0.01, n=290). VisionKeys acuity correlated very well with M&S and children under age 7 scored coarser than teens and young adults. Median distance log arc seconds stereo on VisionKeys (2.00) differed from near Titmus circles (1.78) and PDI Check (1.89, Kruskal-Wallis X2(2)=9.8, p=0.007) however they all correlated well by Bland Altman.

Conclusion: The new, portable VisionKeys system gives valid distance visual acuity with slightly finer estimate compared to M&S and the distance stereo compared well with near Titmus and PDI Check. As such, it should be valuable for testing children and adults in remote locations.