Lubka Naycheva

Transcorneal Electrical Stimulation for Patients with Retinitis Pigmentosa: A Prospective, Randomized, Sham-Controlled Exploratory Study

PURPOSE To assess the safety of transcorneal electrical stimulation (TES) and explore its efficacy in various subjective and objective parameters of visual function in patients with retinitis pigmentosa (RP). METHODS Twenty-four patients in this prospective, randomized, partially blinded, good-clinical-practice study underwent TES (5-ms biphasic pulses; 20 Hz; DTL electrodes) 30 minutes per week for 6 consecutive weeks. The patients were randomly assigned to one of three groups: sham, 66%, or 150% of individual electrical phosphene threshold (EPT). Visual acuity (VA), visual field (VF; kinetic, static), electroretinography (Ganzfeld, multifocal), dark-adaptation (DA), color discrimination, and EPTs were assessed at all visits or four times, according to the study plan. RESULTS TES using DTL electrodes was tolerated well; all patients finished the study. Two adverse (foreign body sensation), but no serious adverse events were encountered. There was a tendency for most functional parameters to improve (8/18) or to remain constant (8/18) in the 150% group. VF area and scotopic b-wave amplitude reached statistical significance (P < 0.027 and P < 0.001, respectively). Only desaturated color discrimination and VF mean sensitivity decreased. There was no obvious trend in the 66% group. CONCLUSIONS TES was found to be safe in RP patients. Positive trends were discovered, but due to the small sample size of this exploratory study, statistical significance was reached only for VF area and scotopic b-wave amplitude. Further studies with larger sample sizes and longer duration are needed to confirm the findings and to define optimal stimulation parameters. (ClinicalTrials.gov number, NCT00804102.).

Gene expression profiling of the retina after transcorneal electrical stimulation in wild-type Brown Norway rats.

PURPOSE Transcorneal electrical stimulation (TES) has been beneficial in several neurodegenerative ocular diseases, but the exact mechanisms remain to be elucidated. This study was conducted to investigate the effects of TES on the retinas of wild-type Brown Norway (BN) rats by gene expression profiling and to assess its effects on retinal function and morphology. METHODS TES was applied to BN wild-type rat retinas in vivo for 1 hour (1-ms biphasic pulses at 20 Hz; 200 μA). RNA was isolated and processed for microarray-based profiling 4 hours after TES; differentially expressed genes from TES compared with those from sham-treated animals were validated by quantitative real-time polymerase chain reaction. Furthermore, the effect of TES was assessed at the structural and functional levels using electroretinography, confocal scanning laser ophthalmoscopy, optical coherence tomography, and immunohistochemistry. RESULTS Transcriptome changes associated with TES versus sham-stimulated BN wild-type retina were identified. Four hundred ninety genes were differentially expressed in TES and included potentially neuroprotective genes such as Bax or members of the tumor necrosis factor family (Tnfrsf11b, Tnrsf12a, Tnfsf13b, Tnfsf13). ERG recordings showed physiological retinal function after TES, and structural in vivo and ex vivo studies revealed intact retinal anatomy. CONCLUSIONS These results demonstrate that TES applied to the retina of the wild-type BN rats induces distinct transcriptome level changes and may help in the understanding of the mechanisms underlying TES. In addition, TES treatment indicates no negative effect on structure and function of the wild-type BN retina up to 35 hours after application.

Transcorneal electrical stimulation shows neuroprotective effects in retinas of light-exposed rats

PURPOSE To examine the effects of transcorneal electrical stimulation (TES) on retinal degeneration of light-exposed rats. METHODS Thirty-three Sprague Dawley albino rats were divided into three groups: STIM (n = 15) received 60 minutes of TES, whereas SHAM (n = 15) received identical sham stimulation 2 hours before exposure to bright light with 16,000 lux; healthy animals (n = 3) served as controls for histology. At baseline and weekly for 3 consecutive weeks, dark- and light-adapted electroretinography was used to assess retinal function. Analysis of the response versus luminance function retrieved the parameters Vmax (saturation amplitude) and k (luminance to reach ½Vmax). Retinal morphology was assessed by histology (hematoxylin-eosin [HE] staining; TUNEL assay) and immunohistochemistry (rhodopsin staining). RESULTS Vmax was higher in the STIM group compared with SHAM 1 week after light damage (mean intra-individual difference between groups 116.06 μV; P = 0.046). The b-wave implicit time for the rod response (0.01 cd.s/m²) was lower in the STIM group compared with the SHAM group 2 weeks after light damage (mean intra-individual difference between groups 5.78 ms; P = 0.023); no other significant differences were found. Histological analyses showed photoreceptor cell death (TUNEL and HE) in SHAM, most pronounced in the superior hemiretina. STIM showed complete outer nuclear layer thickness preservation, reduced photoreceptor cell death, and preserved outer segment length compared with SHAM (HE and rhodopsin). CONCLUSIONS This sham-controlled study shows that TES can protect retinal cells against mild light-induced degeneration in Sprague Dawley rats. These findings could help to establish TES as a treatment in human forms of retinal degenerative disease.

Phosphene thresholds elicited by transcorneal electrical stimulation in healthy subjects and patients with retinal diseases.

PURPOSE To evaluate electrically evoked phosphene thresholds (EPTs) in healthy subjects and in patients with retinal disease and to assess repeatability and possible correlations with common ophthalmologic tests. METHODS In all, 117 individuals participated: healthy subjects (n = 20) and patients with retinitis pigmentosa (RP, n = 30), Stargardts disease (STG, n = 14), retinal artery occlusion (RAO, n = 20), nonarteritic anterior ischemic optic neuropathy (NAION, n = 16), and primary open-angle glaucoma (POAG, n = 17). EPTs were determined at 3, 6, 9, 20, 40, 60, and 80 Hz with 5 + 5-ms biphasic current pulses using DTL electrodes. Subjects were examined twice (test-retest range: 1-6 weeks). An empirical model was developed to describe the current-frequency relationship of EPTs. Visual acuity, visual field (kinetic + static), electrophysiology (RP, RAO, STG: Ganzfeld-electroretinography [ERG]/multifocal-ERG; POAG: pattern-ERG; NAION: VEP), slit-lamp biomicroscopy, fundus examination, and tonometry were assessed. RESULTS EPTS varied between disease groups (20 HZ: healthy subjects: 0.062 ± 0.038 mA; STG: 0.102 ± 0.097 mA; POAG: 0.127 ± 0.09 mA; NAION: 0.244 ± 0.126 mA; RP: 0.371 ± 0.223 mA; RAO: 0.988 ± 1.142 mA). In all groups EPTs were lowest at 20 Hz. In patients with retinal diseases and across all frequencies EPTs were significantly higher than those in healthy subjects, except in STG at 20 Hz (P = 0.09) and 40 Hz (P = 0.17). Test-retest difference at 20 Hz was 0.006 mA in the healthy group and 0.003-0.04 mA in disease groups. CONCLUSIONS Considering the fast, safe, and reliable practicability of EPT testing, this test might be used more often under clinical circumstances. Determination of EPTs could be potentially useful in elucidation of the progress of ophthalmologic diseases, either in addition to standard clinical assessment or under conditions in which these standard tests cannot be used meaningfully. (ClinicalTrials.gov number, NCT00804102.).

Transkorneale Elektrostimulation bei Patienten mit Morbus Stargardt

Stargardts disease is an autosomal recessive inherited juvenile macular degeneration and at present no acknowledged science-based therapy is available for these patients. Recently, reports have been published on the effectiveness of electrical stimulation in experimental animal models and in patients with neurodegenerative ocular disease, particularly retinitis pigmentosa. This study included 12 patients with Stargardts disease who were randomized into one of three groups (n = 4) with 0% (sham), 66% or 150% of the individual electrically stimulated phosphene threshold. Outcome measures of the study were safety and efficacy of transcorneal electrical stimulation (TES) with DTL electrodes in subjective and objective parameters of visual function under therapy. In general TES was well tolerated and no adverse or serious events were noted. Neither Ganzfeld, multifocal ERG, OCT nor visual field testing showed statistically significant changes in any group.

[Effects of transcorneal electrical stimulation in patients with Stargardt's disease].

Stargardts disease is an autosomal recessive inherited juvenile macular degeneration and at present no acknowledged science-based therapy is available for these patients. Recently, reports have been published on the effectiveness of electrical stimulation in experimental animal models and in patients with neurodegenerative ocular disease, particularly retinitis pigmentosa. This study included 12 patients with Stargardts disease who were randomized into one of three groups (n = 4) with 0% (sham), 66% or 150% of the individual electrically stimulated phosphene threshold. Outcome measures of the study were safety and efficacy of transcorneal electrical stimulation (TES) with DTL electrodes in subjective and objective parameters of visual function under therapy. In general TES was well tolerated and no adverse or serious events were noted. Neither Ganzfeld, multifocal ERG, OCT nor visual field testing showed statistically significant changes in any group.

Transkorneale Elektrostimulation bei Patienten mit Morbus Stargardt@@@Effects of transcorneal electrical stimulation in patients with Stargardt’s disease

Stargardts disease is an autosomal recessive inherited juvenile macular degeneration and at present no acknowledged science-based therapy is available for these patients. Recently, reports have been published on the effectiveness of electrical stimulation in experimental animal models and in patients with neurodegenerative ocular disease, particularly retinitis pigmentosa. This study included 12 patients with Stargardts disease who were randomized into one of three groups (n = 4) with 0% (sham), 66% or 150% of the individual electrically stimulated phosphene threshold. Outcome measures of the study were safety and efficacy of transcorneal electrical stimulation (TES) with DTL electrodes in subjective and objective parameters of visual function under therapy. In general TES was well tolerated and no adverse or serious events were noted. Neither Ganzfeld, multifocal ERG, OCT nor visual field testing showed statistically significant changes in any group.