Combined mechanical pressure, electrical stimulation may induce increased ocular damage

Mechanical pressure can cause damage to the retina both alone and with excessive electrical stimulation, according to a study by researchers in California. "Electrical stimulation coupled with mechanical pressure increases the area of the damage," the authors noted.

L. Colodetti and colleagues at the University of Southern California investigated electrically induced retinal damage in normal-sighted adult Long Evans pigmented rats. They inserted a single platinum microelectrode into the vitreous cavity of each animal and applied stimulus pulses for 1 hour at 100 Hz.

The animals were divided into two groups. In the first group, no contact was made between the electrode and the retina, and current pulses of either 0.05 µC/phase or 0.2 µC/phase were applied. In the second group, visible contact, evidenced by a slight dimpling of the retina, was made between the electrode and the retina, and current pulses of 0.09 µC/phase were applied, according to the study.

Control experiments were run both with and without retinal contact and without electrical stimulation.

The rats were survived for 2 weeks, at which point the authors observed changes only in the retinas that had made contact with the electrode, with or without electrical stimulation.

Additionally, the authors performed histological analysis at 2 weeks after sacrifice. They noted significant differences (P < .05) between animals that experienced retinal contact and those that did not in all features of the retina, retinal pigment epithelium and choroid, except in the inner nuclear layer thickness. No difference was found within the groups based on the intensity of electrical stimulus applied, the authors reported.

"The size of the affected area was significantly larger with both retinal contact and electrical stimulation, compared to with retinal contact alone," they said.

This study is published in the July issue of Experimental Eye Research.