Ocular effects of radiofrequency energy

Abstract

Radiofrequency (RF) energy has been reported to cause a variety of ocular effects, primarily cataracts but also effects on the retina, cornea, and other ocular systems. Cataracts have been observed in experimental animals when one eye was exposed to a localized, very high RF field and the other eye was the unexposed control. The results show that 2450 MHz exposures for >or=30 min at power densities causing extremely high dose rates (>or=150 W/kg) and temperatures (>or=41 degrees C) in or near the lens caused cataracts in the rabbit eye. However, cataracts were not observed in the monkey eye exposed to similar exposure conditions, reflecting the different patterns of energy absorption (SAR, specific absorption rate) distribution, due to their different facial structure. Since the monkey head is similar in structure to the human head, the nonhuman primate study showed that the incident power density levels causing cataracts in rabbits and other laboratory animals cannot be directly extrapolated to primates, including human beings. It is reasonable to assume that an SAR that would induce temperatures >or=41 degrees C in or near the lens in the human eye would produce cataracts by the same mechanism (heating) that caused cataracts in the rabbit lens; however, such an exposure would greatly exceed the currently allowable limits for human exposure and would be expected to cause unacceptable effects in other parts of the eye and face. Other ocular effects including corneal lesions, retinal effects, and changes in vascular permeability, have been observed after localized exposure of the eye of laboratory animals to both continuous wave (CW) and pulsed wave (PW) exposures, but the inconsistencies in these results, the failure to independently confirm corneal lesions after CW exposure, the failure to independently confirm retinal effects after PW exposure, and the absence of functional changes in vision are reasons why these ocular effects are not useful in defining an adverse effect level for RF exposure. While cataracts develop after localized exposure of the eye at SARs >or= 150 W/kg, whole body exposure at much lower levels (14-42 W/kg) is lethal to rabbits. Two studies reported cataracts in this animal after 30 daily exposures at SARs at the upper end of the lethal range, e.g., 38-42 W/kg; however, long term exposure of rabbits (23 h/day, 6 months) at 1.5 W/kg (17 W/kg in the rabbit head) did not cause cataracts or other ocular effects. A long term (1-4 years) investigation of monkeys exposed at high SARs (20 and 40 W/kg to the monkey face) found no cataracts or other ocular effects or change in visual capability. The results of these long term studies support the conclusion that clinically significant ocular effects, including cataracts, have not been confirmed in human populations exposed for long periods of time to low level RF energy. The results of four recent human studies show that there is no clear evidence of an association between RF exposure and ocular cancer.

Thermal aspects of exposure to radiofrequency energy: Report of a workshop

“…Based on studies by his group, he concluded that temperatures exceeding 41 C would be required to produce cataracts in the rabbit eye. The present writer notes that this concurs with Elder's conclusion that microwave exposures could produce cataracts in the rabbit, but only at high exposures sufficient to heat the lens to temperatures greater than or equal to 41 C [5]. However, this present writer notes, the issue remains controversial, given the existence of a scattering of literature, mostly involving experiments on cultured lenses, reporting that somewhat lower microwave exposures can induce opacities in lens tissue [13].…”

“…As used in these studies, 'behavioural disruption' refers to the change in behaviour of an animal from an assigned task. This could be either work stoppage or switching to a thermoregulatory behaviour, such as in rats spreading saliva on the tail, a behaviour observed in this species when in warm By contrast, the limits in both the IEEE standard and ICNIRP for partial-body exposure were set on the basis of data showing injury (cataracts) in rabbits at exposure levels above 100 W/kg to the eye, causing local tissue temperatures to increase above 41.5 C in or near the lens [5]. After incorporation of a suitable safety factor, this led to limits for partial body of exposure of 2 and 10 W/kg for the general public and occupational exposures, respectively, averaged over 10 g of tissue.…”

Mobile phones and health: A literature overview

“…The possibility of adverse effects (e. g. cataracts in the lenses) was investigated in several studies. Although, adverse ocular effects were only found for SAR values well above values that occur in the eye from the use of mobile phones [22], there remains some concern about possible adverse health effects from high peak-power, pulsed microwave radiation [93]. Current results, however, support the conclusion that clinically significant ocular effects do not occur for low-level microwave radiation [22].…”

“…This study did not find an increased risk. Overall, there is no clear evidence of an association between mobile phone radiation and ocular cancer [22].…”

Applications of a genetic algorithm for identification of maxima in specific absorption rates in the human eye close to perfectly conducting spectacles

“…Lin [14] reviewed the possibility of cataract formation and showed that the temperature increases were too small to cause cataracts under normal conditions. The Stewart Report [15] includes a brief summary of experimental studies into RF effects on the eye and Elder produced a more detailed analysis [16]. They reported that pulsed RF fields at 2.45GHz, at moderate SAR levels, produced harmful effects in primates including lesions in the corneal endothelium and increased vascular leakage from the blood vessels of the iris.…”