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Hideaki Hirose, Yoshiki Tanaka, Kazuo Ichikawa; A brain-based luminance contrast sensitivity test for screening scotopic sensitivity syndrome.. Invest. Ophthalmol. Vis. Sci. 2020;61(7):3385.
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© ARVO (1962-2015); The Authors (2016-present)
Scotopic sensitivity syndrome (SSS), also known as Meares-Irlen syndrome, is a visual stress that can cause discomfort glare, reading disabilities, and eye strains. Several studies have proved that it is a visual processing problem at the brain level. However, there are still no clinical tests to diagnose it simply and effectively. In this study, we aimed to devise a novel screening test based on brain signals and make clear its effectiveness.
We employed 64 participants who consisted of 40 males and 24 females. They aged from 23 to 74 years old and had healthy eyes. Five persons of them had been suffered from the SSS in their daily lives. We made a screening test as follows and asked them to perform it. It was a form of neurophysiological experiment. Steady-state visual evoked potentials (SSVEPs) and pupil diameter were simultaneously measured while each participant gazed into a flickering visual stimulus. The SSVEPs were collected from the back of the head over the primary visual area. The stimulus shaped like the Ishihara plate and was achromatic. Angular size was 10 degrees. It was presented 10 times for 12 seconds at 3 second intervals. In the presentation duration, luminance contrast was changed from 10 to 20, 35, 50, 65, 80% in order every 2 seconds. Luminance pattern were reversed at 4 Hz frequency. Average luminance of the stimulus and background were 40 cd/m2. We investigated the relationships between amplitude of the SSVEPs, the pupil diameters, and the luminance contrasts of the stimulus.
In most of the normal participants, amplitude of the SSVEPs was the largest when the luminance contrast of the stimulus was above 50%. The peak contrast value tended to be higher in the senior participant than in the young. In contrast, in the SSS participants, amplitude of the SSVEPs was the largest when the luminance contrast was 35%. However, the pupil diameters observed in the SSS participants were not significant differences from ones in the normals.
These test results strongly suggested that the SSS derives from hypersensitivity to luminance information on neural circuits from the retina to the primary visual area, not on the autonomous nervous system. Then, we have come to the conclusion that the screening test which can detect it helped us to classify each person’s sensitivity to supra-threshold luminance contrast easily.
This is a 2020 ARVO Annual Meeting abstract.
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