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.

PURPOSE:The study aimed for objective detection of primary open-angle glaucoma with selective color channel stimulation based on the silent substitution technique. In addition, an objective was analysis of the characteristics of individual color channels based on visual evoked potentials.METHODS:Visual evoked potentials were recorded in 141 subjects (39 patients with glaucoma, 71 healthy subjects, and 31 age-matched healthy subjects) with two scalp electrodes after cone-specific flash stimulation. Silent substitution stimulation was presented with a 30-in. liquid crystal display. Separate responses were obtained for short-, medium-, and long-wavelength-sensitive cones. Age-matched subgroups were used to compare patients with glaucoma and healthy subjects.RESULTS:The S-cone responses of age-matched healthy subjects had significantly different slopes for the first positive wave, compared with the responses of patients with moderate glaucoma. This difference was not observed in the L- and M-cone responses. Distinct changes in the S-cone response profiles were observed with increasing severity of glaucoma. Patients with severe glaucomatous damage were recognizable by the altered profiles of their visual evoked potentials. Healthy subjects showed significant differences between color channels.CONCLUSIONS: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.

The purpose of the work was the objective analysis of the cortical response signals after selective colour channel stimulation. Using the parameters of the visual evoked potential (VEP) we aimed to classify the separate colour channels as well as glaucoma patients and volunteers.On the basis of via the silent substitution technique (SST) flash stimulation, a selective S-cone stimulation and selective L- and M-cone stimulation was performed. 102 healthy subjects and 39 glaucoma patients were studied. The VEPs were recorded, pre-processed and analyzed. Based on the response signals, parameters were extracted. Using the parameters, a classification was done by the use of the binary logistic regression.The S-cone response and the LM-cone response could be differentiated with accuracy about 80%. Volunteers and glaucoma patients of the test group could be classified with overall accuracy of 85% at S-cone response and 76% at LM-cone response. The peak latency and reconstruction error seems to be a meaningful parameter for an effective classification.Good classification results could be achieved for the separate colour channels as well as for volunteers and glaucoma patients. The classification of glaucoma patients was clearly better by the use of the S-cone responses than by the use of LM-cone responses. Larger set of signals, especially from glaucoma patients, would probably improve the classification results.

A problem of stimulators used for electrophysiological examination of the human retina is the impossibility of active stimuli controlling on the fundus. They suffer from lacking information about the retinal area actually stimulated. In this work we present the first application of a novel fundus controlled digital color LCoS (Liquid Crystal on Silicon) projection stimulator. We determined the possibilities for an excitation of the Scone as well as the L- and M-cone pathway. Therefore we used the Silent Substitution Technique (SST) and imaged two different flash sequences on the fundus of three volunteers. Simultaneously to the stimulation electroencephalographic measurements were performed, followed by an analysis of the visual-evoked cortical potentials (VEPs). As a result we observed typical SST-VEP components. Additionally we discovered a time delay of the S-cone response in comparison to the L- and M-cone response. This suggests an effective stimulation of the different pathways.