Abstract
Purpose :
Transcorneal electrical stimulation (TES) has shown beneficial effects in patients with retinitis pigmentosa (RP) exerting effects presumably through the release of neurotrophic factors. After promising results of an exploratory study in 24 patients over 6 weeks (Schatz et al., IOVS 2011) the here presented study assessed safety and efficacy by subjective and objective parameters after 1 year in a cohort of 60 patients. Here, we specifically report on results of the ganzfeld ERG.
Methods :
Fifty-two patients completed the prospective, randomized, partially-blinded study with stimulation of 30 min. per week for 52 consecutive weeks in one eye. Patients were randomly assigned to sham (n=20), 150% (n=15), or 200% (n=17) of their individual electrical phosphene threshold. TES was applied by CE-marked stimulator and electrodes (Okuvision GmbH, Reutlingen, Germany), performed partially at home and in the study center. Ganzfeld ERG was assessed 5 times in regular intervals according to ISCEV standards (rod protocol: 4 steps with intensities from 0.16 to 3 phot cd.s/m and 4 ms duration, a single flash of 3 cd.s/m white 6500 K, and a 9 Hz flicker; cone protocol: a single-flash response of 3 phot cd.s/m with a background illumination of 30 phot cd/m and a 30 Hz flicker). Primary outcome measures were visual field area (Goldmann III/4e), secondary measures the development of electroretinographic parameters.
Results :
The application of TES over the study period was tolerated well. Kinetic visual field results did not reach statistical significance but showed a positive trend. Tendencies of improved function were also observed for scotopic ERG parameters: standard flash a-wave amplitude P=0.60, b-wave amplitude P = 0.084, 9 Hz-flicker: P=0.78 (assessed by a REML test). The photopic ERG standard flash improved by 37% in the 200% group and by 17% in the 150% group in comparison to sham (P<0.0001), implicit times did no show a homogeneous picture; in the 30 Hz flicker changes did not reach statistical significance (P=0.30).
Conclusions :
While only a non-significant trend for improvement was seen in the scotopic ERG and visual field area after 1 year significant improvements of the photopic ERG underline the potential of TES in the treatment of patients with RP. Even longer studies in more patients could presumably clarifiy the definite role of TES in RP.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.