Corneal asphericity and spherical aberration after refractive surgery

PURPOSE: To evaluate changes in corneal asphericity (Q) and spherical aberrations after refractive surgery using Scheimpflug imaging.SETTING: University of California, San Diego, Shiley Eye Center, La Jolla, California, USA.DESIGN: Cohort study.METHODS: After wavefront-guided laser in situ keratomileusis, patients within +/- 0.50 diopter of piano and with an uncorrected distance visual acuity of at least 20/20 were evaluated. the Q values and corneal spherical aberration Zernike values were obtained using Scheimpflug imaging preoperatively and 1 to 3 months postoperatively.RESULTS: the study enrolled 177 myopic eyes and 32 hyperopic eyes. the mean Q value was -0.28 +/- 0.11 (SD) and -0.22 +/- 0.15, respectively, preoperatively and +0.35 +/- 0.44 and -0.64 +/- 0.31, respectively, postoperatively. the asphericity change was highly correlated with preoperative spherical equivalent (r(2) = 0.81; P <=.001). the mean corneal spherical aberration was +0.21 +/- 0.08 mu m in myopic eyes and +0.36 +/- 0.11 mu m in hyperopic eyes preoperatively and +0.36 +/- 0.17 mu m and 0.00 +/- 0.29 mu m, respectively, postoperatively. the corneal spherical aberration changes were correlated with the amount of preoperative refractive error (r(2) = 0.34; P<.001). There was a tendency for Q values and spherical aberrations to become more positive after myopic ablation and more negative after hyperopic ablation.CONCLUSIONS: Myopic and hyperopic corrections induced changes in the Q value and spherical aberrations in opposite directions (ie, positive and negative, respectively). the changes depended on the magnitude of the refractive correction.Research to Prevent Blindness, Inc., New York, New York, USACoordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Univ Calif San Diego, Shiley Eye Ctr, Dept Ophthalmol, La Jolla, CA 92093 USAUniversidade Federal de São Paulo, São Paulo, BrazilUniv Santo Tomas, Manila, PhilippinesUniversidade Federal de São Paulo, EPM, São Paulo, BrazilCAPES: BEX 1325/09-4Web of Scienc