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Millimeter wave absorption in the nonhuman primate eye at 35 GHz and 94 GHz
Steven Chalfin1, John A D'Andrea, Paul D Comeau
1Ophthalmology Department, University of Texas Health Science Center, San Antonio 78229-3900, USA. chalfin@uthscsa.edu
Abstract:
The purpose of this study was to evaluate anterior segment bioeffects of pulsed 35 GHz and 94 GHz microwave exposure in the nonhuman primate eye. Five juvenile rhesus monkeys (Macaca mulatta) underwent baseline anterior segment ocular assessment consisting of slit lamp examination, corneal topography, specular microscopy, and pachymetry. These studies were repeated after exposure of one eye to pulsed 35 GHz or 94 GHz microwaves at varied fluences, with the other eye serving as a control. The mean fluence required to produce a threshold corneal lesion (faint epithelial edema and fluorescein staining) was 7.5 J cm(-2) at 35 GHz and 5 J cm(-2) at 94 GHz. Transient changes in corneal topography and pachymetry were noted at these fluences. Endothelial cell counts remained unchanged. Threshold corneal injury from 35 GHz and 94 GHz microwave exposure is produced at fluences below those previously reported for CO2 laser radiation. These data may help elucidate the mechanism of thermal injury to the cornea, and resolve discrepancies between IEEE C95.1 (1999), NCRP (1986), and ICNIRP (1998) safety standards for exposure to non-ionizing radiation at millimeter wavelengths.
Insights
Pulsed millimeter-wave exposure at 35 GHz and 94 GHz can cause corneal injury in nonhuman primate eyes. The threshold for injury is lower than previously reported for CO2 laser radiation.
Area of Science:
- Ophthalmology
- Biophysics
- Electromagnetic Engineering
Background:
- Non-ionizing radiation safety standards for millimeter wavelengths have discrepancies.
- Understanding the bioeffects of millimeter-wave exposure on the eye is crucial for public health and safety.
Purpose of the Study:
- To evaluate the anterior segment bioeffects of pulsed 35 GHz and 94 GHz microwave exposure in nonhuman primate eyes.
- To determine the threshold for corneal injury from millimeter-wave exposure.
Main Methods:
- Five juvenile rhesus monkeys were used, with one eye exposed to microwaves and the other serving as a control.
- Anterior segment ocular assessments included slit lamp examination, corneal topography, specular microscopy, and pachymetry.
- Fluence levels were varied to determine the threshold for corneal lesions.
Main Results:
- The mean threshold fluence for corneal lesions was 7.5 J/cm² at 35 GHz and 5 J/cm² at 94 GHz.
- Transient changes in corneal topography and pachymetry were observed.
- Endothelial cell counts remained unchanged.
Conclusions:
- Threshold corneal injury from 35 GHz and 94 GHz microwave exposure occurs at lower fluences than CO2 laser radiation.
- These findings may help elucidate thermal injury mechanisms and resolve discrepancies in safety standards for millimeter-wave non-ionizing radiation.