Effects of Ocular Direct Current Stimulation on Full Field Electroretinogram

Area of Science:

• Ophthalmology
• Neuroscience
• Medical Devices

Background:

• Weak current stimulation is explored for neurological disorders, with ocular applications for diseases like glaucoma suggested by positive effects on retinal nerve cells.
• Previous studies noted pattern-reversal electroretinogram (PERG) amplitude changes during ocular direct current stimulation, but the specific retinal cells involved remained unclear.
• The PERG signal modulation could stem from pre-ganglion cell activity or alterations in ganglion cell responses.

Purpose of the Study:

• To investigate the acute effects of ocular direct current stimulation on pre-ganglion retinal cells, specifically cones and bipolar cells.
• To clarify whether pre-ganglion cells contribute to the observed changes in PERG signals during ocular current stimulation.

Main Methods:

• Full-field electroretinograms (ERGs) were recorded from 15 subjects before and during ocular direct current stimulation (800 μA for 5 min).
• Stimulation involved cathodal, anodal, or sham polarity applied via a ring electrode around the eye.
• ERG a-wave, b-wave, and b'-wave amplitudes and latencies were analyzed using Wilcoxon signed-rank and Friedman tests.

Main Results:

• No significant changes in ERG wave amplitudes or latencies were observed during ocular direct current stimulation compared to baseline.
• No significant differences were found between cathodal, anodal, and sham stimulation conditions.
• The results indicate that pre-ganglion cells (cones and bipolar cells) are not significantly affected by the applied current stimulation.

Conclusions:

• Acute ocular direct current stimulation at 800 μA does not appear to modulate the activity of pre-ganglion retinal cells.
• The findings suggest that the previously reported effects on PERG signals during ocular current stimulation are unlikely to originate from pre-ganglion cells.
• Further research is needed to identify the specific retinal cell populations responsible for PERG modulations.