Transcorneal electrical stimulation for the treatment of retinitis pigmentosa: results from the TESOLAUK trial

Abstract

Objective: To explore the impact of weekly transcorneal electrical stimulation (TES) over a 6-month period as a treatment for retinitis pigmentosa (RP).

Methods and analysis: A prospective open-label observational trial was carried out assessing weekly TES in participants with RP for a period of 6 months followed by observation for a further 6 months. Clinical examination and investigations were carried out at 3 monthly intervals for a total of 12 months. The primary outcome measure explored safety through a descriptive analysis of adverse effects with secondary outcome measures evaluating structural and functional efficacy.

Results: Seven male and seven female participants with RP aged 18-80 years were recruited. TES was well tolerated with no serious adverse events reported. Two participants reported transient foreign body sensation and one participant had discomfort underneath the skin electrode. Following 6 months of TES, best-corrected visual acuity increased by 1.1±1.4 letters in the control arm and 0.93±1.4 letters in the treated arm. Central microperimetry threshold sensitivity rose by 0.02±0.5 decibels (dB) and 0.37±0.4 dB and Goldmann visual field volume by 0.16±0.09 steradians (sr) vs 0.22±0.12 sr for the control and treated eye, respectively. There was no statistical significance seen between eyes following the treatment or observation period.

Conclusion: This small open-label clinical trial showed that TES was safe and well tolerated in patients with RP. Visual function measurements at 6 months demonstrated no significant difference between the control and treated eyes. The results justify a larger clinical trial over a longer period of time in order to identify any treatment effect.

Keywords: clinical trial; degeneration; genetics; retina; treatment other.

Conflict of interest statement

Competing interests: All authors except FG were employed by the National Health Service at the time of this work taking place. SD: has previously received support to attend educational meetings from Novartis, a Novartis grant to develop the AMD service and the employer has received funds from Novartis to allow SD to speak at educational events. REM: Director of NightstaRx, a choroideremia gene therapy company established by the University of Oxford and funded by the Wellcome Trust. The company had no role in the conduct, funding or writing up of this study.

Figures

Figure 1

Flow chart illustrating the recruitment and progress of participants. The most frequent reason for exclusion was the presence of cystoid macular oedema (due to the independent variability in this clinical feature of RP, which would influence visual acuity readings). All participants completed the 6-month treatment period, although two withdrew during the observation period for personal reasons. TES, transcorneal electrical stimulation.

Figure 2

Graph demonstrating the change in central parameters of central retinal thickness (CRT) as measured by optical coherence tomography (OCT) and threshold sensitivity of the central 10 degrees using the MAIA microperimeter (MP). There was no statistical significance noted between the control eye and treated eye following the treatment period (CRT: P=0.91, MP: P=0.68) or the observation period (CRT: P=0.52, MP: P=0.43).

Figure 3

Graph demonstrating the change in peripheral parameters of mean annular radius using autofluorescence (AF) and volume of Goldmann visual field (GVF). There was no statistical significance noted between the control eye and treated eye following the treatment period (AF: P=0.16, GVF: P=0.58) or the observation period (AF: P=0.64, MP: P=0.91).