Study type: Medical/biological study (experimental study)

Absence of corneal endothelium injury in non-human primates treated with and without ophthalmologic drugs and exposed to 2.8 GHz pulsed microwaves. med./bio.

Published in: Bioelectromagnetics 2010; 31 (4): 324-333

Aim of study (acc. to author)

To study the effects of pulsed microwaves and the interaction of opthalmologic drugs (Timolol and Xalatan) on corneal endothelial damage in four adult Rhesus monkeys under anesthesia in order to confirm the results of previous studies (Kues et al. 1985 and Kues et al. 1992) reporting a microwave-induced corneal endothelial damage at a low threshold (2.6 W/kg). Additionally, previous studies reported that vasoactive ophthalmologic medications lowered the threshold by a factor of 10 to 0.26 W/kg.

Background/further details

A nine-exposure regimen was selected for experiment I. Drug sensitization of microwave-induced corneal endothelial injury in experiment II (one year later) followed the three-exposure regimen of Kues et al. (Kues et al. 1992).
In Experiment I, ophthalmologic examinations were conducted before and 7, 30, 90, and 180 days after exposures. In Experiment II, ophthalmologic examinations were done 7, 30, 90, and 180 days after exposures.

Endpoint

Exposure

Exposure Parameters
Exposure 1: 2.8 GHz
Modulation type: pulsed
Exposure duration: continuous for 4 hr/day, 3 days/week for 3 weeks
experiment 1
Exposure 2: 2.8 GHz
Modulation type: pulsed
Exposure duration: continuous for 4 hr/day on 3 or 7 days
experiment 2

General information

Experiment 2 was executed one year after experiment 1. In experiment 2 subjects were pretreated with 0.5 % Timolol maleate and 0.005 % Xalatan(R) before exposure to pulsed microwaves

Exposure 1

Main characteristics
Frequency 2.8 GHz
Type
Charakteristic
Exposure duration continuous for 4 hr/day, 3 days/week for 3 weeks
Additional info experiment 1
Modulation
Modulation type pulsed
Pulse width 1.5 µs
Repetition frequency 34 Hz
Exposure setup
Exposure source
Setup rectangular waveguide connected to a 2.44 m x 3.66 m x 2.44 m anechoic chamber, lined with 15 cm Eccosorb cones; aluminum-flanged WR284 waveguide and a pressure plate located at the end of the microwave transmission line were used as an open-ended waveguide antenna; surface of the subject's eyes centerd in the boresight of the open-ended waveguide antenna at a distance of 20 cm
Parameters
Measurand Value Type Method Mass Remarks
power 29 W average over time measured - -
power density 13 mW/cm² average over time measured - -
power density 464 mW/cm² peak value measured - -
power density 14.2 mW/cm² average over time measured - at 20 cm from the pressure plate

Exposure 2

Main characteristics
Frequency 2.8 GHz
Type
Charakteristic
Exposure duration continuous for 4 hr/day on 3 or 7 days
Additional info experiment 2
Modulation
Modulation type pulsed
Pulse width 1.5 µs
Repetition frequency 34 Hz
Exposure setup
Exposure source
Parameters
Measurand Value Type Method Mass Remarks
power 29 W average over time measured - -
power density 13 mW/cm² average over time measured - -
power density 464 mW/cm² peak value measured - -
power density 14.2 mW/cm² average over time measured - at 20 cm from the pressure plate

Exposed system:

Methods Endpoint/measurement parameters/methodology

Investigated system:
Investigated organ system:
Time of investigation:
  • before exposure
  • during exposure
  • after exposure

Main outcome of study (acc. to author)

The microwave exposure resulted in a 1.0-1.2°C increase in eyelid temperature, but the absolute temperature never exceeded 38°C, a level well below the known damage threshold. Pulsed microwave exposure did not cause alterations in corneal endothelial cell density and corneal thickness with or without ophthalmologic drugs.
Therefore, the authors conclude that previously reported changes in the cornea exposed to pulsed microwaves were not confirmed at exposure levels that are more than an order of magnitude higher.

Study character:

Study funded by

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