Effects of high peak power microwaves on the retina of the Rhesus monkey

Abstract

We studied the retinal effects of 1.25 GHz high peak power microwaves in Rhesus monkeys. Preexposure fundus photographs, retinal angiograms, and electroretinograms (ERG) were obtained to screen for normal ocular structure and function and, after exposure, as endpoints of the study. Histopathology of the retina was an additional endpoint. Seventeen monkeys were randomly assigned to receive sham exposure or pulsed microwave exposures. Microwaves were delivered anteriorly to the face at 0, 4.3, 8.4, or 20.2 W/kg spatially and temporally averaged retinal specific absorption rates (R-SAR). The pulse characteristics were 1.04 MW ( approximately 1.30 MW/kg temporal peak R-SAR), 5.59 micros pulse length at 0, 0.59, 1. 18, and 2.79 Hz pulse repetition rates. Exposure was 4 h per day and 3 days per week for 3 weeks, for a total of nine exposures. The preexposure and postexposure fundus pictures and angiograms were all within normal limits. The response of cone photoreceptors to light flash was enhanced in monkeys exposed at 8.4 or 20.2 W/kg R-SAR, but not in monkeys exposed at 4.3 W/kg R-SAR. Scotopic (rod) response, maximum (combined cone and rod) response, and Naka-Rushton R(max) and log K of scotopic b-waves were all within normal range. Retinal histopathology revealed the presence of enhanced glycogen storage in photoreceptors among sham (2/5), 8.4 W/kg (3/3), and 20.2 W/kg (2/5) exposed monkeys, while enhanced glycogen storage was not observed in the 4.3 W/kg (0/4) exposed group. Supranormal cone photoreceptor b-wave was R-SAR dependent and may be an early indicator of mild injury. However no evidence of degenerative changes and ERG depression was seen. We concluded that retinal injury is very unlikely at 4 W/kg. Functional changes that occur at higher R-SAR are probably reversible since we saw no evidence of histopathologic correlation with ERG changes. Bioelectromagnetics 21:439-454, 2000. Published 2000 Wiley-Liss, Inc.

Recent Advances in Research on Radiofrequency Fields and Health

“…Lu et al (2000) studied the retinal effects of 1.25 GHz high peak power microwaves in Rhesus monkeys, using fundus photographs, retinal angiograms and electroretinograms to evaluate ocular structure and function. The authors concluded that retinal injury is unlikely at 4 W/kg, and that functional changes at higher retinal SAR values are likely reversible.…”

No influence of acute RF exposure (GSM‐900, GSM‐1800, and UMTS) on mouse retinal ganglion cell responses under constant temperature conditions

“…Retinal degeneration in monkeys was also found by Kues and Monahan [] for SAR values in excess of 3.9 W/kg (2.45 GHz pulsed microwave) and 3.5 W/kg (1.25 GHz pulsed microwave). Lu et al [] showed that cone photoreceptor b‐wave from monkey electroretinogram (ERG) was SAR dependent and was enhanced by SAR values of 8.4 and 20.2 W/kg, but not by 4.3 W/kg. No degenerative change or ERG depression was seen in this study.…”

“…In other in vitro studies on neuronal responses, which found effects of RF‐EMF on neuronal function, it remains unclear how good the temperature was controlled during measurements [Hossmann and Hermann, ]. With respect to retinal effects, an in vivo study on rhesus monkey retina by Lu et al [] is in agreement with our results when considering SAR values below 8.4 W/kg. Scotopic b‐waves in the electroretinogram (ERG) were within normal range for SAR values up to 20.2 W/kg.…”

“…One of the critical organs that might be damaged by RF‐EMF is the eye, due to its relative proximity to the radiation source during normal mobile phone use. Many studies focused on possible injuries of monkey, human, or rabbit eyes and the visual system in response to EMF exposure of various intensities, frequencies, and modulations [Lu et al, ; Schmid et al, ; Irlenbusch et al, ]. Cornea and lens of the eye are clearly damaged by excessive temperature rise induced by high specific absorption rates (SAR) [Carpenter, ; Kues et al, ; Kues and Monahan, ].…”

Chronic Electromagnetic Exposure at Occupational Safety Level Does Not Affect the Metabolic Profile nor Cornea Healing after LASIK Surgery

“…Although no mechanism has been clearly exposed, some authors have identified deleterious effects in different parts of the eye, such as the lens [11–13], the cornea [14, 15], or the retina [15]. Such results were frequently related to an oxidative stress increase [16].…”