UNSCHEDULED DNA-SYNTHESIS FOLLOWING EXCIMER LASER ABLATION OF THE CORNEA INVIVO

The amount of unscheduled DNA synthesis (UDS) produced in the cells adjacent to excimer laser ablations in the cornea was compared for 193-nm and 248-nm laser wavelengths. UDS is interpreted to indicate the process of excision repair of pyrimidine dimers formed in DNA. 193-nm laser ablation did not produce a statistically significant difference in the amount of UDS as compared to a negative control (diamond-knife corneal incision). However, 248-nm laser ablation did produce a highly statistically significant difference in the amount of UDS as compared to both the negative control (P < 0.001) and the 193-nm laser irradiation (P < 0.001). Other forms of DNA damage (single-strand DNA chain breaks and DNA-protein crosslinks) are not measurable by UDS and need to be investigated in the evaluation of the oncogenic potential of 193-nm laser ablation.