Increased sensitivity of the non-human primate eye to microwave radiation following ophthalmic drug pretreatment.

Abstract

Previous studies in our laboratory have established that pulsed microwaves at 2.45 GHz and 10 mW/cm2 are associated with production of corneal endothelial lesions and with disruption of the blood-aqueous barrier in the non-human primate eye. In the study reported here we examined ocular damage in monkeys (M. mulatta and M. fascicularis) following topical treatment with one of two ophthalmic drugs (timolol maleate and pilocarpine) that preceded exposure to pulsed microwaves. Anesthetized monkeys were sham exposed or exposed to pulsed, 2.45 GHz microwaves (10 microseconds, 100 pps) at average power densities of 0.2, 1, 5, 10, or 15 mW/cm2 4 h a day for 3 consecutive days (respective SARs were 0.052, 0.26, 1.3, 2.6, and 3.9 W/kg). Immediately before microwave exposure, one or both eyes were treated topically with one drop of 0.5% timolol maleate or of 2% pilocarpine. Following administration of a drug, we observed a significant reduction in the power-density threshold (from 10 to 1 mW/cm2) for induction of corneal endothelial lesions and for increased vascular permeability of the iris. Diagnostic procedures (in vivo specular microscopy and fluorescein iris angiography) were performed following each exposure protocol. In addition, increased vascular permeability was confirmed with horseradish peroxidase tracer techniques. Although we did not measure intraocular temperatures in experimental animals, the results suggest that a mechanism other than significant heating of the eye is involved. Our data indicate that pulsed microwaves at an average SAR of 0.26 W/kg, if administered after pretreatment with ophthalmic drugs, can produce significant ocular effects in the anesthetized primate.

AI evidence extraction

Main findings

In anesthetized monkeys pretreated topically with timolol maleate or pilocarpine, the reported power-density threshold for induction of corneal endothelial lesions and increased iris vascular permeability decreased from 10 to 1 mW/cm2 during pulsed 2.45 GHz microwave exposure. The authors report significant ocular effects at an average SAR of 0.26 W/kg when exposure followed ophthalmic drug pretreatment.

Outcomes measured

• Corneal endothelial lesions
• Blood-aqueous barrier disruption / increased vascular permeability of the iris

Limitations

• Sample size not reported in abstract
• Intraocular temperatures were not measured
• Details of randomization/blinding not described in abstract

Suggested hubs

• who-icnirp (0.2)
  Animal study reporting ocular effects at specified SAR/power density; potentially relevant to exposure guideline discussions.

{
    "study_type": "animal",
    "exposure": {
        "band": "microwave",
        "source": null,
        "frequency_mhz": 2450,
        "sar_wkg": 0.2600000000000000088817841970012523233890533447265625,
        "duration": "4 h/day for 3 consecutive days; pulsed (10 microseconds, 100 pps)"
    },
    "population": "Non-human primates (monkeys: Macaca mulatta and Macaca fascicularis), anesthetized",
    "sample_size": null,
    "outcomes": [
        "Corneal endothelial lesions",
        "Blood-aqueous barrier disruption / increased vascular permeability of the iris"
    ],
    "main_findings": "In anesthetized monkeys pretreated topically with timolol maleate or pilocarpine, the reported power-density threshold for induction of corneal endothelial lesions and increased iris vascular permeability decreased from 10 to 1 mW/cm2 during pulsed 2.45 GHz microwave exposure. The authors report significant ocular effects at an average SAR of 0.26 W/kg when exposure followed ophthalmic drug pretreatment.",
    "effect_direction": "harm",
    "limitations": [
        "Sample size not reported in abstract",
        "Intraocular temperatures were not measured",
        "Details of randomization/blinding not described in abstract"
    ],
    "evidence_strength": "low",
    "confidence": 0.7800000000000000266453525910037569701671600341796875,
    "peer_reviewed_likely": "yes",
    "keywords": [
        "non-human primate",
        "monkey",
        "Macaca mulatta",
        "Macaca fascicularis",
        "microwave",
        "2.45 GHz",
        "pulsed microwaves",
        "SAR",
        "timolol maleate",
        "pilocarpine",
        "corneal endothelial lesions",
        "iris vascular permeability",
        "blood-aqueous barrier"
    ],
    "suggested_hubs": [
        {
            "slug": "who-icnirp",
            "weight": 0.200000000000000011102230246251565404236316680908203125,
            "reason": "Animal study reporting ocular effects at specified SAR/power density; potentially relevant to exposure guideline discussions."
        }
    ]
}

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