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R.A. Schuchard, A. Chow, C. Barnes, J. Kotowski, G. Dagnelie, J. Pollack, ASR® Device Study Group; Contrast Sensitivity in People With the Subretinal Artificial Silicon RetinaTM Microchip Device . Invest. Ophthalmol. Vis. Sci. 2006;47(13):3210.
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To evaluate contrast sensitivity (luminance and color separately) for people with RP implanted with the subretinal ASR device (Optobionics Corp.).
Luminance and color contrast sensitivity testing was performed with 20 people with RP enrolled in the Phase II trial. As some subjects had moderate to severe vision loss that prevented accurate testing with the Pelli–Robson chart and PV–16 color test, additional tests were developed to allow testing in all subjects. Luminance contrast was determined with gratings that were 0.3 logMAR above the subject's threshold grating acuity. A projection system displayed contrast gratings with 0.075 logContrast steps in four possible orientations (up, down, diagonal right, or diagonal left) for a 4–alternative forced choice adaptive staircase paradigm. Color contrast was tested with a detection task using PV–16 similar caps (Chow High/Low Saturation Color Test). One color cap (yellow, green, orange, blue, or red) was mixed with nine achromatic caps with a range of illuminances around the illuminance of the color cap. If the high saturation color cap was detected, then a low saturation cap with the same chromaticity was also tested. Subjects also rated their abilities to see different shades of grey and color in everyday objects. Subjects were assessed at baseline and then at one, two, three, four, six, and nine months post–operatively with the majority of subjects starting testing post–operatively
Subjects had logContrast values of 0.075 to 1.875 and 0.25 to 1.40 for grating and Pelli–Robson testing, respectively. Subjects had color responses from 117 to 467 color difference scores and 0/0 to 10/10 color caps detected for PV–16 and Chow color test, respectively. Linear regressions (slope of performance with time) were done to assess whether subjects had the same, improved, or worse contrast sensitivity. Color results showed 33% / 58% better, 42% / 33% same, and 25% / 8% worse in testing / rating evaluations. Luminance results showed 42% / 58% better, 42% / 33% same, and 17% / 8% worse in testing / rating evaluations. Contingency analysis found that the controlled testing and self–reported rating responses generally do not agree (Kappa value of –0.24 and –0.16 for luminance and color, respectively).
The additional luminance grating and color cap tests allowed all subjects to be tested for luminance contrast and color contrast. Self–reported improvements in color and contrast vision may not correspond to controlled testing.
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