The effects of nuclear magnetic resonance imaging on ocular tissues

Nuclear magnetic resonance, an imaging technique with great promise for detecting cerebral abnormalities, was studied to determine its possible deleterious effects on the mammalian eye. Young (3.5-week-old) Columbia-Sherman rats were exposed simultaneously to a constant magnetic field of 2.7 tesla and radio frequency pulses of 29 MHz at 800-ms intervals for six hours at field strengths representing the maximum used in a clinical setting. The six-hour exposure is many times greater than the four to six minutes currently employed in most diagnostic protocols. The animals were examined by slit-lamp biomicroscopy and ophthalmoscopy at regular intervals. Autoradiograms of lenses from animals injected with tritiated thymidine prior to exposure did not reveal any disturbances in cell-cycle kinetics. Eyes from rats not previously injected with the isotope were processed for cytopathologic analysis at various intervals. A two-year follow-up has indicated that at both the slit-lamp biomicroscopic and the light microscopic levels, there were no discernable effects on the rat eye.