Table 3.
Transorbital and Transpalpebral ES: Clinical Studies
| Reference | Disease | Experimental population; stimulation location | Control group | ES parameters | Evaluation method | Results |
|---|---|---|---|---|---|---|
| Bola et al, 201448 | Chronic prechiasmatic visual system damage | Seven patients; skin near the eyeball | Eight patients; sham | Current strength above (125%) phosphene thresholds as reported by the patients; applies for 10 days, 40 minutes each | EEG recording | ES strengthened α band functional connectivity, which was associated with perceptual improvements |
| Fedorov et al, 201149 | OND | 446 patients; upper eye lid | — | Intensity increase stepwise by 10 μA per second, 5 Hz, two to nine pulses; each daily session of 200–250 cycles with five to seven 1-minute breaks, session length 25–40 minutes; 10-day treatment | EEG recording, VF, VA | ES improved VF size in both eyes; VA was significantly increased in both eyes; increased α and θ power in patients who had VF enlargements but no VA change; nonresponders exhibited increased Δ power spectra in occipital and frontal areas |
| Gall et al, 201050 | OND | One patient; skin of the eye lids; both eyes | — | The amplitude was always <600 μA, 10–30 Hz, 10–15 pulses, single duration of 8.7 ± 0.8 milliseconds, 30–40-minute duration, daily for 10 days; intensity increase stepwise by 10 μA per second | VA; VF; static and kinetic perimetry | Detection ability increased; mean perimetric threshold increased |
| Gall et al, 201151 | OND | 24 patients; near the eyeball; both eyes | 18 Patients; sham | Intensity increase stepwise by 10 μA per second, 5 Hz, pulse shape was either square or sinus, two to nine pulses; each session of 200–250 cycles with five to seven 1-minute breaks; 10-day treatment | VF diagnostics with HRP; VA and contrast vision | Detection ability was significantly larger; static and kinetic perimetry provided ES efficacy |
| Sabel et al, 201152 | OND | 12 patients; near the eyeball | 10 Patients; sham | The amplitude of pulses was <1000 μA; current intensity increased stepwise by 10 μA per second; two to nine pulses | HRP; VA; EEG recording | Stimulation resulted in improvement of a VF by 69%; increased temporal procession of visual stimuli |
| Schmidt et al, 201353 | Prechiasmatic partial OND | 18 patients; orbital; both eyes | Six patients; sham | Maximal amplitude <500 μA, 9–37 Hz, two to nine pulses, 10 consecutive days | EEG recording; VF | Enhancement of α activity after ES; the residual VF was significantly improved |
| Anastassiou et al, 201354 | Dry AMD | 12 patients; palpebral; both eyes | 10 Patients; sham | 150–220 μA, 5–80 Hz; 5 consecutive days, two sessions on each day, every session eight spots (40 seconds/spot) | VA testing before treatment, after 5 days, after 4 weeks, after 6 months; macular sensitivity and fixation stability with microperimetry; OCT | Stimulation resulted in improved VA in 7 of 12 patients, with more than five letters; contrast sensitivity showed a similar pattern |
| Chaikin et al, 201555 | Wet and dry AMD | 17 patients; 25 eyes with dry type and 6 eyes with wet type | — | 150 μA; 3–162 Hz; 35-minute session once a week; average number of treatments was 4.8 | IO pressure measurements; OCT; VA | Significant improvements in VA in patients with dry type, but not in wet type; in dry-type subjects, 52% of patients exhibited increased VA, and 26% deterioration |
| Shinoda et al, 200856 | Wet and dry AMD | 21 patients; 16 (27 eyes) with wet type and 5 (7 eyes) with dry type; palpebral; both eyes | — | 800 μA; one 20-minute session was performed four times per day, up to 1 month; 290 Hz for 1 minute, 31 Hz for 2 minutes, 8.9 Hz for 10 minutes, 0.28 Hz for 7 minutes | BCVA before and after 4 weeks; slit-lamp examination; funduscopy; fluorescein angiography; automated static VF testing | All of the patients reported phosphene perception; BCVA improved, but did not reach statistical significance |
AMD, age-related macular degeneration; BCVA, best-corrected visual acuity; EEG, electroencephalogram; ES, electrical stimulation; HRP, high-resolution perimetry; IO, intraocular; OND, optic nerve damage; OCT, optical coherence tomography; VA, visual acuity; VF, visual field; –, not reported.