Abstract
Purpose:
To assess efficacy of treatment and explore high responders to transcorneal electrical stimulation (TES) in patients with retinitis pigmentosa (RP).
Methods:
63 eyes of 63 patients with RP (33 m, 30 f, age range 19-74) were treated with TES (5 ms + 5 ms biphasic pulses at 20 Hz). TES was applied for 30 minutes weekly for 52 consecutive weeks with an OkuEl®-transcorneal electrode and an OkuStim®-Device (Okuvision GmbH, Germany). Patients were randomly assigned to three study aims: TES with 0 mA (sham, n = 22); 150% (n = 21) or 200% (n = 20) of the individual electrical phosphene threshold (EPT) current at 20 Hz. Best corrected visual acuity, ophthalmological examination (slit-lamp biomicroscopy, fundus examination, Goldmann-applanation tonometry) and EPT were determined at baseline and at 8 following visits (at week 10, 16, 22, 28, 34, 40, 46 and 52). At 5 visits (at week 1, 16, 28, 40 and 52) kinetic visual field (VF) (Octopus 900®, Haag-Streit, Germany), optical coherence tomography (Spectralis®-OCT, Heidelberg Engineering GmbH, Germany), full-field electroretinography and dark adaptation were performed. To identify high responders, patients were divided into 3 groups according to the baseline size of the VF area using stimulus Goldmann III4e: small (234-2447 deg²), medium (2628-6792 deg²) and large (6806-14587 deg²) VF area.
Results:
52 patients (27 m, 25 f; TES = sham: n = 20, TES = 150%: n = 15 and TES = 200%: n = 17) completed the entire study. Using restricted maximum likelihood (REML) for estimation of changes under treatment (P < 0.05, Tukey-Kramer), in the group with small VF area (n = 18) a positive tendency for VF area enlargement (P = 0.14) was detected, but statistical significance was not reached. In the groups with medium (n = 18) and large (n = 18) VF area no such tendency was observed (respectively P = 0.62 and P = 0.21).
Conclusions:
A positive tendency for an enlargement of VF area was observed in the group with the smallest VF area. However, results were not statistically significant. Particularly, patients with a smaller VF area (below ~27 deg) seem to benefit more from TES and could be classified as high responders.