Abstract
Purpose :
Millimeter wave (MMW) technologies are using in the field of communications, sensing, imaging, and spectroscopy in daily life. A few corneal damage thresholds by MMW exposure studies have been performed. We propose the mathematical model to estimate threshold incident power levels of MMW based on CEM43°C (cumulative number of equivalent minutes at 43°C) criterion.
Methods :
Pigmented rabbits (N=54, Dutch, 12-15 week-old) were exposed unilaterally to 10-400 mW/cm2 40, 75, and 95 GHz band MMW for 6 min at the center of the pupillary area, with a lens antenna. Anterior damage was examined by slit lamp. CEM43°C criterion is the index of “thermal iso-effective dose”, which is originally applied for cancer therapy from 1984. Coupled analysis for electromagnetic field (EMF) and heat transport (HT) was performed from 40 to 95 GHz with 100 µm spatial resolution. In the heat transport simulation, convectional heat transfer model, driven by aqueous humor in the anterior chamber, was considered.
Results :
Corneal damage induced by 40, 75 and 95 GHz MMW differed with 40<75<95 GHz being more severe. Three-dimensional time development temperature distributions were obtained during MMW exposure by varying incident power density from 50-300 mW/cm2 at each frequency to obtain threshold. Moreover, 3D time dependent CEM43°C index distribution within the corneal region was calculated from these time dependent temperature data. Threshold levels of incident power density for 360 sec exposure was estimated from these CEM43°C data in the condition of acute and minor damage as for cornea, which was described in the past literature as 21<CEM43°C<40 min. Consequently, threshold levels estimated by this mathematical model were consistent with those obtained by in vivo rabbit experiments.
Conclusions :
Our proposed model with CEM43°C criterion is feasible to estimate threshold power levels for corneal epithelium damage.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.