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

Shin Tsu Lu, Satnam P. Mathur, Bruce Stuck, Harry Zwick, John A. D'Andrea, John M. Ziriax, James H. Merritt, Gerard Lutty, D. Scott McLeod, Mary Johnson

Research output: Contribution to journalArticlepeer-review


We studied the retinal effects of 1.25GHz 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 1.04MW (≈ 1.30MW/kg temporal peak R-SAR), 5.59μs pulse length at 0, 0.59, 1.18, and 2.79Hz pulse repetition rares. Exposure was 4h 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 Rmax 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. Published 2000 Wiley-Liss, Inc.

Original languageEnglish (US)
Pages (from-to)439-454
Number of pages16
Issue number6
StatePublished - Sep 2000


  • Electroretinogram
  • Fundus photograph
  • Retinal angiogram
  • Retinal histopathology

ASJC Scopus subject areas

  • Biophysics
  • Physiology
  • Radiology Nuclear Medicine and imaging


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