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Miguel Castelo-Branco, Bruno Quendera, Mohammed Al-Rawi, Sónia Ferreira; Novel psychophysical approaches identify impairment of motion, achromatic and chromatic discrimination in early diabetic retinopathy. Invest. Ophthalmol. Vis. Sci. 2014;55(13):3535.
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To detect early function changes in the presence or absence diabetic retinopathy (DR) using three novel 2AFC (two-alternative forced choice) psychophysical discrimination tests (independent variables: motion, achromatic and chromatic L, M and S cone contrasts) between two separated moving single dots at four distinct meridians.
We assessed one hundred participants (50 diabetics and 50 controls) using a novel psychophysical approach allowing for multi psychophysical channel testing. The study included two-alternative forced-choice test for speed discrimination and achromatic contrast discrimination. We also tested chromatic L, M and S cone contrasts in order to test the discrimination at the following locations in the visual field: 5° nasal vs. temporal; 7.5° upper vs. lower and 10° nasal upper vs. temporal lower and nasal lower vs. temporal upper. To assess the macular region, we used color fundus photography following ETDRS and OCT Spectralis macular thickness maps. Our tests required the comparison and discrimination of a visual feature (motion, achromatic contrast and chromatic contrast) between two separated moving single dots (a reference dot and a target dot). It is important to note that reference and target dots were presented in opposite hemifields. The use of similar stimuli allows for better comparison across visual channels because the tested dimension (related to distinct pathways) was distinct for every procedure (motion, achromatic and achromatic contrast) but stimuli were physically similar across the other dimensions that were not manipulated in the psychophysical staircase.Parametric statistical tests were set at a p value threshold of 0.05.
We found significant changes (p<0.05) in diabetic participants vs. controls for all psychophysical tested channels ( speed, achromatic, chromatic L and chromatic S). Notably, significant changes in motion and achromatic channels were also identified in diabetic patients in the absence of diabetic retinopathy.
Visual psychophysical testing across multiple visual channels, using a fast forced choice discrimination strategy can be used to monitor psychophysical impairment in diabetes and even detect dysfunction in the pre-retinopathy stage.
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