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L.A. Kim, T. Winter, T.T. Lam, M.S. Humayun, A.A. Sadun; Retinal Prosthetic and Circadian Rhythms . Invest. Ophthalmol. Vis. Sci. 2005;46(13):1524.
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In addition to providing the substrate for conscious vision, the eye also regulates circadian rhythms. We investigated the potential to mediate this system artificially through retinal prostheses in blind patients. Two advanced RP patients with retinal implants and a normal control had saliva melatonin levels regularly assayed to quantify their circadian rhythms.
In this prospective study, we examined two subjects who had RP and were NLP for several decades. They, and a normal control, had multiple saliva samples taken over the course of 4 days and assayed for melatonin. The subjects then had surgical implantation of the retinal prosthetic implant. In one subject the prosthesis was electrically stimulated. Both test subjects were then evaluated with serial saliva sampling over the course of 4 days. Melatonin concentrations in saliva samples were doubly measured using a commercially available melatonin ELISA assay (n = 83).
The control subject showed regular circadian levels of melatonin with morning peaks and day time lows while both test subjects with advanced RP had no periodicity of melatonin levels pre–operatively (Figure A, B). After surgical implantation of the retinal prosthetic, both subjects (with and without stimulation respectively) showed some periodicity for three out of the four days in saliva melatonin concentrations (Figure C, D), with morning peaks and day time suppression of melatonin levels, as would be expected from a normal circadian rhythm.
These results suggest that (1) implantation surgery of the retinal prosthetic alone may play a role in modulating melatonin levels, and (2) patients who have little vision function may benefit from surgical implantation of the retinal prosthetic beyond conscious visual perception.
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