No Forward Shifting of Posterior Corneal Surface in Eyes Undergoing LASIK

The change in internal aberrations following myopic corneal laser refractive surgery

“…However, some slit-scanning topography studies have found no changes to the posterior cornea post-LASIK [37,38], and Ueda et al [39] demonstrated that these posterior corneal changes are artefacts due to changes in the magnification ratio. This is further supported by Scheimpflug imaging studies demonstrating no posterior corneal changes following LASIK [40,41]. The posterior curvature as determined by slit scanning and Placido technology is dependent on the anterior curvature, and questions have been raised regarding its accuracy and reproducibility [42][43][44], whereas with Scheimpflug imaging, the posterior curvature is independent of the anterior curvature.…”

Intraobserver and interobserver repeatability of curvature and aberrometric measurements of the posterior corneal surface in normal eyes using Scheimpflug photography

“…[4][5][6][7] In addition, they have been used as control parameters of corneal stability during the follow-up of patients who have had laser in situ keratomileusis (LASIK). [8][9][10][11][12][13][14][15] In any case, there is controversy regarding posterior corneal surface changes after keratorefractive procedures with the excimer laser because of concerns over the accuracy of the available measuring systems. 8,12,[16][17][18] Two technologies for measuring the posterior corneal surface have been described: combined scanning-slit and Placido-disk technology 19 (Orbscan system, Bausch & Lomb) and Scheimpflug photography 20 (Pentacam system, Oculus Optikgeräte).…”

Validity of the keratometric index: Evaluation by the Pentacam rotating Scheimpflug camera

“…25 In eyes after uneventful laser in situ keratomileusis or photorefractive keratectomy, the Pentacam did not show the apparent ectasia in the posterior corneal surface that was commonly shown by the Orbscan, and this has been strongly suspected of not being a true physical phenomenon. 21,26 In this study, we used the Pentacam device to measure the anterior and posterior corneal surface elevations. The radius of the BFS was determined for both the anterior and posterior corneal surfaces.…”