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Florian Gekeler, Mariya Gosheva, Lubka Naycheva, Johanna Pach, Gabriel Willmann, Eberhart Zrenner, Andreas Schatz; Transcorneal electrical stimulation for retinitis pigmentosa - a prospective sham-controlled follow-up study over 1 year in 63 patients. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):3801.
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<br /> After the encouraging results of the first study (EST1; Schatz et al. IOVS 2011) with significant increase of visual field area and scotopic b-wave amplitude after 6 weeks of transcorneal electrical stimulation (TES) this 1 year-trial was set up to assess efficacy and safety in patients with retinitis pigmentosa (RP).
<br /> In this prospective, randomized, partially blinded study 63 patients (age 19-74; m:f=33:30) underwent TES (5-ms biphasic pulses@20 Hz, 30 minutes per week for 1 year) using the OkuEl®-DTL electrode and an OkuStim®-stimulator (Okuvision GmbH, Germany). Patients were randomly assigned to sham, 150%, or 200% stimulation current of their individual electrical phosphene threshold. Primary outcome measure was visual field area (VFA; Goldmann III/4e), secondary outcome measures ganzfeld and mfERG values, BCVA, threshold to full field blue and red light (FST; Diagnosys), most assessed in week 1, 10, 16, 22, 28, 40, 46, 52.
<br /> Fifty-two patients (27 m, 25 w; TES=sham: n=20, TES=150%: n=15 and TES=200%: n=17) completed the study. Adverse events (AEs) were dry eye symptoms (82% of all patients, significantly more in stimulated eyes), ocular missensations, corneal erosion, macular edema (all not related to treatment, sham/partner eyes). No serious AEs related to the treatment were observed. VFA decreased 9% less in the 200% group, showing a tendency but not reaching significance (REML, p=0.19). BCVA, FST also showed only tendencies but no statistical significance (REML, p=0.38, =0.40, =0.70, resp.).
<br /> TES was found to be safe, AEs were mainly dry eye feelings always treatable by artificial tears. Primary and secondary outcome measure showed positive tendencies but did not reach levels of statistical significance. Notably, as phosphene thresholds decreased under treatment, the sunken stimulation currents might have counteracted efficacy and achievement of significance levels in VFA. Exploratory analyses on high responders were promising to identify patients who might benefit from TES.
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