Glaucoma and its severity were objectively detected by using the silent substitution technique. The stimulation technique and signal analysis enabled assessment of the visual evoked potentials of individual color channels.
We design, characterize, and apply a novel optoelectrophysiological setup for a fundus-controlled silent substitution technique that accounts for interindividual variability in retina morphology and simultaneously monitors the stimulation site under investigation. We connect a digital color liquid crystal on silicon projector, an electron-multiplying imager, and a light-emitting diode to a fundus camera. The temporal and spatial characterization reveal a maximal contrast loss of 7% for the highest stimulation frequency (30 Hz) and maximum cutoff spatial frequencies of ∼120 cycles∕deg. Two silent substitution flash sequences are applied to modulate selective activity in the short-wavelength-sensitive cone (S-cone) and combined long- and middle-wavelength-sensitive cone (LM-cone) pathways. Simultaneously, the visual evoked potentials are recorded. The data are compared to the grand average responses from a previous study that employed standard computer-screen presentation and showed very good latency matches. All the volunteers in the present examination exhibit differences between the S-cone and LM-cone evoked potentials (parameters mean values: peak-to-peak amplitude, N1 latency, and P1 latency for S-cone∕LM-cone responses: 8 μV∕15 μV, 113 ms∕89 ms, 170 ms∕143 ms). We demonstrate that the developed optoelectrophysiological setup simultaneously provides imaging, functional stimulation, and electrophysiological investigation of the retina.
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