Ocular effects of GaAs lasers and near infrared radiation

Abstract

Fiber optic communication systems present a possible or potential hazard to the eyes of engineers and technicians who work with or maintain these systems. To investigate this hypothesis, the retinas of macaque monkeys were exposed to near infrared cw radiation and to GaAs lasers modulated at 22 MHz and 1600 Hz. Trained animals (two) were exposed monocularly under normal physiological conditions to modulated GaAs lasers for several months, on a 5 day/week basis, 1000 sec/day. No loss of visual function or funduscopically visible damage was detected. One of these animals was sacrificed and examined histologically for damage. No differences were detected between the foveae of the exposed and control eyes in this monkey. The radiant exposure in J · cm−2 required to produce minimal lesions was determined on anesthetized animals for cw radiation at three wavelengths (820, 860, 910 nm) and for radiation at 830 nm from a GaAs laser modulated at a digital rate of 44 Mbit/sec. It required from 6 to 8.4 mW of GaAs radiation entering the eye for periods ranging from 400 to 3000 sec to produce a detectable lesion. Since the spot size on the retina was <50 μm in diameter, it is difficult if not impossible to imagine how the human eye could remain focused on such a source for an appreciable time, even if 8 mW were entering the pupil. Extrapolation to man is always dangerous, but these experiments do not suggest that engineers and technicians operating and maintaining fiber optic communication systems are subject to an ocular risk unless they use magnification optics.