Detection of laser accumulative effects on the retina using different techniques

Abstract

The electroretinogram (ERG), histological and biospeckle photography techniques have been used to study the accumulative effects of a low-power He - Ne laser after repeated extended exposure of the eye. The results obtained by these techniques showed a very good correlation. They indicated that repeated prolonged exposure of the eye, even to low power lasers, induced significant damage to retinal cells, depending on the delivered dose. At low doses (constant power of and varying exposure time up to 20 min), the b-wave of ERG has decreased in amplitude due to membrane permeability changes. A histological change was found in both the pigmented epithelium (PE) and photoreceptor (PH) layers of the retina as an elongation in PE processes and a slight angulation of the PH layer. By increasing the laser dose, the change in membrane permeability increased causing swelling of retinal cells (as indicated by light microscope photographs), small b-wave amplitude and the appearance of the spreading depression wave (SD). Moreover, using a biospeckle photography technique, the visibility of obtained fringes has been changed due to changes of the retinal surface configuration which indicated that the biospeckle photography technique might be used as an additional tool for retinal investigation.