Corneal higher-order aberrations induced by overnight orthokeratology.

PURPOSE: To evaluate corneal higher-order aberrations induced by overnight orthokeratology for myopia. DESIGN: Prospective, noncomparative, consecutive, interventional case series. METHODS: A prospective study was conducted in 64 eyes of 39 patients with overnight orthokeratology for myopia, who were followed up for at least 3 months and attained uncorrected visual acuity of 20/20 or better. Corneal height data were obtained with computerized videokeratography (TMS-2N, Tomey), and wavefront aberration was derived using Zernike polynomials. Higher-order aberrations of the cornea were calculated for 3- and 6-mm pupils. RESULTS: Orthokeratology significantly reduced manifest refraction from -2.60 +/- 1.13 (mean +/- SD) diopters to -0.17 +/- 0.31 diopters (P < .0001, paired t test). Root-mean-square (RMS) of third-order (coma-like) aberrations significantly increased by orthokeratology for both 3-mm (P < .0001, paired t test) and 6-mm (P < .0001) pupils. Fourth-order RMS (spherical-like) aberrations increased significantly by the treatment for both 3-mm (P < .0001) and 6-mm (P < .0001) pupils. Vertical coma significantly changed from positive to negative for both 3-mm (P = .0323) and 6-mm (P < .0001) pupils. Horizontal coma significantly increased to the positive direction for both 3-mm (P < .0001) and 6-mm (P < .0001) pupils. Increases in the third- and fourth-order RMS showed significant positive correlations with the amount of myopic correction for 3-mm (Pearson correlation coefficient, r = .452, P = .0001 for third-order RMS, r = .381, P = .0017 for fourth-order RMS) and 6-mm (r = .499, P < .0001, r = .455, P = .0001) pupils. CONCLUSIONS: Corneal higher-order aberrations significantly increased, even in clinically successful orthokeratology cases. The increases in the higher-order aberrations correlated with the magnitude of myopic correction.

Corneal iron ring formation associated with overnight orthokeratology.

PURPOSE: To describe a case of iron deposition in both eyes after overnight orthokeratology. METHODS: This is a case report of a 31-year-old man who underwent overnight orthokeratology. The subject was fitted with rigid gas-permeable contact lenses of reverse-geometry design to correct myopia. RESULTS: The prefitting manifest refraction was -4.75 -0.25 x 175 in the right eye and -4.50 -0.25 x 175 in the left eye. There was no corneal abnormality until 9 months after treatment, but development of corneal arcuate lines in both eyes was observed at the 1-year follow-up visit. Visual acuity was not affected. The deposition pattern corresponded to the outside border of central flatter zone, as shown on the corneal topography map. CONCLUSION: The current findings suggest that tear pooling between the corneal surface and the back surface of the contact lens plays a role in the development of corneal iron ring after orthokeratology with reverse-geometry contact lenses.

Influence of overnight orthokeratology on corneal endothelium.

PURPOSE: To evaluate the influence of overnight orthokeratology on the corneal endothelium. METHODS: Fifty-two eyes of 31 patients undergoing overnight orthokeratology for myopia were examined. They wore the lens every night and were followed up for at least 1 year. The corneal endothelium was examined with specular microscopy to calculate mean endothelial cell density, coefficient of variation of cell area, and percentage of hexagonal cells. Data obtained at 1-year follow-up examinations were compared with those at the baseline examinations using a paired t test. RESULTS: Orthokeratology significantly reduced manifest refraction from -2.32 +/- 1.18 D (mean +/- standard deviation) to -0.16 +/- 0.33 D (P < 0.0001) and improved uncorrected visual acuity from 0.77 +/- 0.29 to -0.07 +/- 0.10 logMAR (P < 0.0001). The endothelial cell density did not change significantly (2879 +/- 231 cells/mm before and 2864 +/- 260 cells/mm after treatment, P = 0.252). The coefficient of variation of cell area was 22.3 +/- 2.7 at baseline and 22.1 +/- 2.4 at 1-year posttreatment, which did not change significantly (P = 0.537). The percentage of hexagonal cells was 72.8 +/- 10.2% pretreatment and 72.5 +/- 10.9% posttreatment (P = 0.800). CONCLUSIONS: Overnight orthokeratology for 1 year did not influence the density or morphology of corneal endothelial cells.

Quantitative evaluation of regular and irregular corneal astigmatism in patients having overnight orthokeratology.

PURPOSE: To quantitatively assess changes in regular and irregular corneal astigmatism in patients having overnight orthokeratology. SETTING: Matsumoto Eye Clinic, Ibaraki, Japan. METHODS: A prospective study was conducted of 64 eyes of 39 patients having overnight orthokeratology for myopia. Inclusion criteria were an uncorrected visual acuity (UCVA) of 20/20 or better after treatment and a minimum follow-up of 3 months. Using Fourier series harmonic analysis, videokeratography data were decomposed into spherical component, regular astigmatism, asymmetry (tilt or decentration), and higher-order irregularity. RESULTS: Orthokeratology significantly reduced the manifest refraction from -2.60 diopters (D) +/- 1.13 (SD) to -0.17 +/- 0.31 D (P<.0001, paired t test) and improved the UCVA from 0.82 +/- 0.30 to -0.11 +/- 0.06 logMAR (P<.0001). Regular astigmatism increased significantly from 0.53 +/- 0.23 D preoperatively to 0.63 +/- 0.40 D postoperatively (P =.0206). The asymmetry component increased significantly from 0.35 +/- 0.22 D to 0.64 +/- 0.40 D (P<.0001). Higher-order irregularity did not change significantly: 0.14 +/- 0.11 D before treatment and 0.17 +/- 0.20 D after treatment (P =.2166). The amount of myopic correction correlated significantly with the increase in the asymmetry component (Pearson correlation coefficient, R = 0.40, P =.0009) but not with the increase in regular astigmatism (R = 0.24, P =.055). CONCLUSIONS: Irregular corneal astigmatism significantly increased, even in clinically successful orthokeratology cases. The effect of the changes on visual function should be studied further.