Discussion
RP, CRAO, branch RAO, pain, retinal diseases, glaucoma
PHOSPHENE, PHOSPHENES, GLAUCOMA, RETINAL DISEASES
To the best of our knowledge, this study is the first clinical trial to assess the efficacy and safety of transdermal electrical stimulation with a skin electrode in patients with CRAO.Consequently, this study included CRAO patients with various baseline values. The change in logMAR vision from 0 to 12 weeks in each case showed a large difference among the cases, and no constant tendency to improve vision was observed. Similar results were obtained for ETDRS visual acuity, MD, and Esterman test scores of the HFA.An increase in the level of IGF-1 [Phosphenes are visual perceptions induced by stimuli other than light. Electrically evoked phosphene thresholds have been used as indicators of electrical stimulation of RGC and have been used, for example, in the evaluation of implanted artificial retinas. Naycheva et al. investigated electrical phosphene thresholds in healthy subjects and patients with retinal diseases and glaucoma [Heyreh et al. reported that CRAO improved spontaneously in two of 21 eyes (10%) even 1 month after onset [There are very few reports of electrical stimulation therapy for CRAO. Inomata et al. performed TES therapy (20 Hz, 30 minutes, up to 1100 μA, once a month for 3 months) in two patients with CRAO (15 and 33 months, respectively), and one with branch RAO (26 months) and reported that the BCVA improved by more than 0.2 logMAR units in the two CRAO cases and the visual fields of Goldmann perimetry were improved in all the three cases [Decimal visual acuities were converted to logMAR units for statistical analyses in this study because the decimal chart prevails in Asia in clinical practice.However, previous studies have demonstrated that decimal charts have several disadvantages [Regarding safety evaluation, electrical stimulation therapy was completed according to the protocol for all five patients. No patient dropped out due to irritation or pain caused by electrical stimulation, and there was no problem with tolerability to electrical stimulation. No AEs related to this therapy were observed during the study. Thus, it can be concluded that TdES was safe under the stimulation protocol implemented in this study.The limitations of this study include the small number of cases, lack of control groups, and short treatment and observation periods. Larger long-term trials with control groups are required. Due to these limitations, we cannot conclude about the efficacy of TdES for CRAO in this study. Furthermore, as mentioned above, the effect of CRAO in the early post-onset period, which is expected to be more effective, has not been verified; the phosphene thresholds and ERG have not been measured. Evaluating these parameters may provide insight into the relationship between the residual retinal function and the effectiveness of electrical stimulation therapy.In conclusion, the effects of TdES therapy on visual acuity and visual field in CRAO patients were unclear in this exploratory trial; however, no serious AEs occurred, and the treatment was tolerated. The logMAR visual acuity was slightly improved and was maintained in two patients in this study, and the safety of TdES treatment was confirmed in both this study and our previous study in patients with RP (11). Since CRAO has no established treatment method, further research into the effects of TdES treatment in CRAO patients may be beneficial.