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H. Kanda, T. Morimoto, T. Miyoshi, Y. Hirohara, T. Mihashi, T. Fujikado; Evaluation of Spatial Resolution of Retinal Prosthesis Using Suprachoroidal-Transretinal Stimulation (STS) by Retinal Optical Imaging. Invest. Ophthalmol. Vis. Sci. 2010;51(13):3017.
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© ARVO (1962-2015); The Authors (2016-present)
Suprachoroidal-Transretinal Stimulation (STS) is one of the electrical stimulation methods for retinal prosthesis (Kanda, IOVS 2004). In this study, in order to investigate if retinal optical imaging can evaluate spatial-resolution that is obtainable with a retinal prosthesis using STS, we measured the spatial distribution of the retinal reflectance changes in response to STS.
Two eyes of two cats were studied under general anesthesia. A stimulating electrode array was inserted into the scleral pocket at the posterior pole of the eye. The electrode arrays consisted of two platinum electrodes (0.5 mm each in diameter). Center-to-center distances of the two electrodes were 0.7 mm or 1.5 mm. Biphasic pulses of 0.3-1.0 mA in amplitude, 0.5 ms/phase in duration, and 20 Hz in frequency were applied to the retina for 4 second on each trial. Fundus images in the near-infrared (820-880 nm) were obtained in every 25 ms for 2 sec before the stimulus, then for 4 sec during the stimulus and finally 20 sec after the stimulus (Okawa, IOVS, 2007). The trials were repeated for 10 times. Subtracting a pre-stimulus image from a post-stimulus image, two-dimensional topography of reflectance change was constructed. To improve signal to noise ratio, the data were averaged for 100 times.
Single electrode stimulation evoked the reflectance changes in localized area near the stimulating electrode at the current of 0.3 to 1.0 mA. On the other hand, simultaneous stimulation with two electrodes evoked the reflectance changes in two different retinal areas. The each area was well localized in the each electrode poison. It indicates that two-point discrimination can be achieved by STS in the retina.
The results showed that retinal optical imaging is an effective method for evaluating spatial resolution of retinal prosthesis.
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