Posterior corneal surface changes after refractive surgery☆
Section snippets
Materials and methods
Informed consent was obtained from all patients before they entered the study, which was approved by the Institutional Review Board of the Massachusetts Eye and Ear Infirmary.
Methods of topographic measurement
The mean time interval between t1 and t2 was 84.95 ± 40.14 days. The data are summarized in Table 1. The float method showed the lowest variation when the mean of the differences were analyzed (CV range, 1.22–3.81), followed by the ABC (CV range, 1.67–2.66) and the PED (CV range, 3.39–5.63) methods. The ABC and PED values showed a high inverse correlation between the CV and the diameter used for the topography test (ABC, r = −0.85, slope = −0.14, P = 0.02; PED, r = −0.81, slope = −0.27, P =
Discussion
Errors analyzing the central cornea have been found in Placido disk-based systems8, 9, 10, 11 as intraobserver and interobserver variability errors.12 Although the technology used in the present study has the advantage that it is not dependent on spherical assumption and the exact focus and center are of less concern,8 there have been no reports evaluating the reproducibility and accuracy of this relatively new technology. In this study, we observed that PRK (in low myopia) and LASIK (in
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Cited by (42)
Changes in posterior corneal elevation after laser in situ keratomileusis enhancement
2008, Journal of Cataract and Refractive SurgeryAnalysis of ectasia after laser in situ keratomileusis: Risk factors
2007, Journal of Cataract and Refractive SurgeryCorneal changes after laser refractive surgery for myopia: Comparison of Orbscan II and Pentacam findings
2007, Journal of Cataract and Refractive SurgeryCitation Excerpt :In their control group, Miyata et al.9 found a mean difference of 2.6 ± 5.7 μm between 2 P-CE measurements obtained 1 month apart in preoperative eyes. Significant post-LASIK increases in P-ME have been reported by Wang et al.1 and Sharma et al.6 Finally, by investigating the changes in the P-BFS, Twa et al.10 reported a steepening of 0.1 mm while Hernández-Quintela et al.5 found no significant difference between PRK, LASIK, and normal groups. All the above studies were based on Orbscan or Orbscan II measurements.
May Consultation # 2
2007, Journal of Cataract and Refractive SurgeryRepeatability and Reproducibility of Posterior Corneal Curvature Measurements by Combined Scanning-Slit and Placido-Disc Topography after LASIK
2006, OphthalmologyCitation Excerpt :This has the least variation compared with the apex-fixed best-fit corneal curvature and posterior elevation in normal corneas.15,36 In the float method, the best-fit sphere (BFS) was allowed to float with no alignment constraints applied to the reference sphere when assessing best fit to the data surface.15,36 Throughout the study, we documented the BFS radius (in millimeters) of the posterior corneal surface using the BFS calculation option.15,36
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Supported in part by the New England Corneal Transplant Research Fund; Research to Prevent Blindness Lew R. Wasserman Merit Award, New York, New York (DTA); Massachusetts Lions Eye Research Award, Boston (DTA); the Fundacion UNAM, México (EHQ); the Asociación para Evitar la Ceguera en México (EHQ); and the Consejo Nacional de Ciencia y Tecnologı́a, México City, Mexico (grant no.: 116681 [EHQ]).