Modulating Ocular/Retinal Blood Flow and Visual Function in Retinitis Pigmentosa

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Many retinitis pigmentosa (RP) patients seek alternative therapies because of the lack of current management options beyond nutritional supplements attempting to slow disease progression. The potential for a beneficial effect on visual function in RP following electroacupuncture and/or transcorneal electrical stimulation (TES) is suggested by research on physiological changes in the eye or brain in response to these therapies. In addition, both our group and others have documented that the majority of RP patients treated with TES, acupuncture or electroacupuncture had improvements in visual function. While these findings are intriguing, the potential mechanisms that may play a role have not been explored in RP. We are interested in studying some of the most promising alternative therapies to determine whether they have a physiologically plausible basis for improving vision in RP, which would provide a scientific rationale for and guide the design of a future randomized controlled trial. A significant increase in blood flow velocity and decreased vascular resistance was measured in the retrobulbar arteries during needling of vision-related acupoints, but not for non-vision-related acupoints, in normal subjects. Thus, ocular and retinal blood flow (ORBF) could serve as an indicator of physiological changes that occur in response to electroacupuncture. We aim to characterize the temporal relationships between changes in ORBF velocity or oxygenation and either improvements or reductions in visual function in RP. We expect to find positive correlations between reductions in ORBF and vision measures within- and across subjects with varying stages of RP disease progression. We hypothesize that subjects with significantly larger improvements in RBF and more recent vision loss will be more likely to develop improvements in visual function in corresponding retinal areas after either electroacupuncture and/or TES. Specifically, we propose to: 1) Examine longitudinal, repeated measures of ORBF in RP patients with recent decline in visual function. We will determine the variability and reproducibility of ORBF velocity, OBF resistance and RBF oxygenation measures over 3 months. 2) Test for possible improvements in ORBF and visual function measures in RP patients receiving electroacupuncture and TES in a crossover trial. We will determine if the magnitude and duration of the ORBF changes post-treatment are related to RP disease severity (retinal thickness and/or sensitivity) and/or vision test changes. We will attempt to determine the temporality (i.e. lag or correspondence) between these physiological and psychophysical measures. The goal of this clinical research project is to determine if evidence exists to support the hypotheses that reductions in ORBF are associated with visual function loss across RP patients, and that their ORBF can improve after treatment with electroacupuncture and/or TES. The results of this work could provide a rationale for the development of potential management options targeted at improving ORBF, and consequently visual function, in this disease.