Microwave diathermy of the retina and choroid
P. T. Finger, P. P. Svitra, S. A. McCormick and A. Presser
Department of Ophthalmology, North Shore University Hospital-Cornell University Medical College, Manhasset, NY 11030.
Microwaves were used to induce chorioretinal scar formation in normal
rabbit eyes. We have developed a directional 6.8-gigahertz microwave
applicator with a rectangular aperture. It was designed to mimic the shape
and function of a T-shaped scleral depressor. For treatment, the applicator
was placed on the conjunctiva over the sclera. Then, indentation was used
to visualize probe placement during indirect ophthalmoscopy.
Thermocouple-controlled heating was initiated such that conjunctival
temperatures in a range of 51 degrees C to 65 degrees C were induced for 10
seconds per treatment. We found that treatment at temperatures of 51
degrees C or 52 degrees C for 10 seconds produced circular areas of acute
retinal whitening. From these microwave-induced lesions, there evolved
chorioretinal attenuation with and without evidence of retinal pigment
epithelial hyperplasia. No evidence of scleral damage was noted at these
thermal doses.
