Corneal Power Determination with Corneal Tomography after Refractive Surgery with Excimer Laser

Abstract

Introduction. The determination of corneal power, after excimer laser refractive surgery, is difficult. Different alternatives with the use of corneal tomographs have been used for this measurement. Objective. To evaluate various methods of determination of corneal power in patients undergoing photorefractive surgery, including diagnostic tests with quantitative measurements. Methodology. This is a retrospective observational study. We included patients undergoing photorefractive surgery with refractive results and postoperative corneal tomography taken at least ten weeks after surgery. Results. In the myopic eyes significant differences were found in the value determined by the keratometry derived from the clinical history when compared with the average postoperative manual keratometry, the simulated keratometry and the Mean Pupil Power of the Sirius® tomograph. On the other hand, when averaging the average postoperative manual keratometry with the postoperative Mean Pupil Power (value called K_{pop average 1}) and comparing it with the keratometry derived by the clinical history method, no statistically significant differences were observed in the myopic patients. Likewise, when averaging the simulated postoperative keratometry of the Sirius® equipment with the postoperative Mean Pupil Power (value called “K_{pop
average 2}”) and comparing it with the keratometry derived by the method of the clinical history, no statistically significant differences were observed in the myopic patients. On the other hand, in hyperopic eyes and with mixed astigmatism, mean errors of the postoperative Mean Pupil Power, with respect to the keratometry derived by the clinical history method, were not significantly different from the errors when comparing the “_{Kpop average 1}” and the “K_{pop average 2}” with the keratometry derived by the clinical history method. Conclusions. In myopic eyes the postoperative corneal power determinations with the “K_{pop average 1}” and “K_{pop average 2}” are closer to the keratometry derived by the clinical history method than to the measurements of the average postoperative manual keratometry, the postoperative simulated keratometry or the Mean Pupil Power of the Sirius® equipment. [Jaramillo LC, Galvis V., Tello A., Camacho PA, Castillo A., Pareja LA. Corneal power determination with corneal tomography after refractive surgery with excimer laser. MedUNAB. 2018;21(1):16-30. doi:1029375/01237047.2397].