Central Corneal Ablation Depth Research Articles

Wavefront properties of the anterior and posterior corneal surface after transepithelial photorefractive keratectomy in myopia.

The present study aimed to evaluate the changes of corneal higher-order aberrations (HOAs) after transepithelial photorefractive keratectomy (TransPRK) in patients with myopia. A total of 80 eyes of 80 patients with myopia with or without astigmatism were evaluated. Prior to and 1 year after the surgery, uncorrected and corrected distance visual acuity in logMAR were assessed. Wavefront aberrations on the anterior surface of the cornea, as well as the posterior and total cornea, were measured via Pentacam. The HOA of the anterior surface and total values of spherical and coma aberrations increased significantly (P<0.001). However, HOAs of the anterior surface, and posterior and total values of the trefoil were not significantly changed (P=0.442, 0.805 and 0.936, respectively). A significant correlation of the pre-operative mean spherical equivalent refraction (MSER), astigmatism and central corneal ablation depth (CCAD) with the changes in coma aberration (r=0.268, P=0.016; r=0.260, P=0.020; r=0.323, P=0.004, respectively) and HOA (r=0.554, P<0.001; r=0.312, P=0.005; r=0.583, P<0.001, respectively) of the anterior surface of the cornea was determined. Furthermore, a significant correlation of the pre-operative MSER and CCAD with the changes in spherical aberration of the anterior corneal surface (r=0.462, P<0.001; r=0.510, P<0.001, respectively) was obtained. In conclusion, TransPRK offers an effective option for improving visual function in patients with myopia. The anterior corneal HOA, as well as spherical and coma aberrations, were significantly increased post-operatively. The HOA of the posterior cornea was not significantly changed. The change in the trefoil aberration was significantly correlated with pre-operative astigmatism, but the pre- and post-operative values were not significantly different.

Intraocular Pressure Change after Laser In Situ Keratomileusis (LASIK)

To analyze the relationship between change in intraocular pressure (IOP) after laser in situ keratomileusis (LASIK), and preoperative central-corneal thickness (CCT), and central-corneal ablation depth (CCAD), a prospective study was conducted of 30 patients (60 eyes) with myopia or myopic astigmatism who underwent LASIK and who were followed up for a mean of 6 months. The parameters evaluated included IOP 1 week preoperatively and 3 months postoperatively, pre- and postoperative CCT, and CCAD; in addition, the anterior ocular segment and the fundus were examined, as was the apparent and cycloplegic refraction. There were 11 male patients and 19 female patients (mean age, 28.3 years) involved in the study. Mean IOP readings were 14.9 mmHg 1 week preoperatively, and 8.3 mmHg 3 months postoperatively; thus, the mean decrease in IOP after LASIK was 6.6 mmHg. Mean values for preoperative CCT, postoperative CCT, and CCAD were 537.2+/-34.7 microm, 434.0+/-32.5 microm, and 101.6+/-23.90 microm, respectively. IOP correlated with CCT both pre- and postoperatively. The mean change in IOP after LASIK for myopia and myopic astigmatism was statistically significant, but did not correlate with CCAD or age. We postulate that CCAD is not a significant predictor of IOP after LASIK.