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H. Kanda, T. Morimoto, T. Fujikado, Y. Tano; Localized Phosphene Elicited by Transscleral Electrical Stimulation in Normal Subjects . Invest. Ophthalmol. Vis. Sci. 2006;47(13):3201.
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© ARVO (1962-2015); The Authors (2016-present)
We have reported that a newly developed method for retinal prosthesis, Suprachoroidal–Transretinal Stimulation (STS), was effective in RCS rats (Kanda, IOVS 2004) and cats (Kanda, ARVO 2005). In order to estimate the effective pulse parameters for STS in clinical study, we examine phosphene elicited by transscleral electrical stimulation with various pulse parameters in normal subjects.
Phosphene elicited by transscleral electrical stimulation was examined in six normal subjects. A stimulating electrode (platinum ball, diameter: 1.0 mm) was set on the conjunctiva in the upper temporal quadrant at a distance 18 mm from the corneal limbus under local anesthesia while subject is gazing inferonasally. A return electrode (Ag–AgCl) was placed on the ipsilateral wrist. Pulse trains with charge–balanced biphasic pulses were applied to the stimulating electrode. We examined the relationship between the phosphenes and the pulse parameters (duration ranging from 0.5 to 4.0 ms, frequency 5 to 100 Hz, inter pulse interval 0 to 4 ms, and number of pulses 1 to 50). Subjects were interviewed about the brightness and the size of phosphene. The study completely fulfils declaration of Helsinki.
All subjects reported single round–shaped phosphenes in response to stimulation. The shorter the pulse duration was, the more localized the phosphene was perceived. The brightness of phosphenes varied according to the pulse parameters. The brightest phosphene was elicited with pulse trains of more than five pulses, duration of less than 0.5 ms, and frequency 20 to 50 Hz.
When pulse parameters were optimized, localized phosphene was elicited by transscleral electrical stimulation of the retina, as a preliminarily test for human STS study. These results suggested the availability of STS for clinical trial. In addition, the optimum pulse parameters in this experiment may be applied for clinical use.
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