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Hyperopic excimer laser refractive surgery involves the ablation of peripheral cornea to increase the curvature of the center.1 However, this abrupt increase in corneal curvature from the periphery to the center2 may result in complications. Despite several technical recommendations that have been proposed to prevent complications,3,4 the development of a whitish corneal apical scar may still be observed,5,6 especially after high hyperopic corrections,5 if not properly done. This corneal scar always occurs beneath the epithelium after excimer laser surface ablation regardless of whether the ablation is done under a flap (LASIK) or directly under the epithelium (surface ablation such as photorefractive keratectomy [PRK]). It is always associated with high eccentricity values (e)4 and corresponds to the point of maximum corneal curvature gradient and steepening. The scar often occurs within the first year after surgery4,6 and invariably hampers visual acuity. The etiology of this scar remains controversial, and the most convincing hypothesis comes from the observation of corneal ectasia.
Mean values of central and peripheral epithelial thickness after extreme hyperopic ablation are comparable to those of keratoconic eyes.7 It has been hypothesized that, when the epithelium reaches a thickness of approximately 20 to 25 µm, there may not be enough cells to keep it viable and epithelial breakdown may occur, possibly leading to scar formation.3 Thus, although not specifically proven, it is not unreasonable to assume that extreme hyperopic ablation, with excessive thinning of the epithelium, may, similarly to keratoconus, induce an apical syndrome.
In the past, proposed treatments included anterior lamellar keratoplasty8 and phototherapeutic keratectomy (PTK).5 However, in our experience, simple PTK is often unable to fix the problem completely and permanently. The scar may recur5 and a second surgical procedure might be necessary.
The current study evaluated the long-term results of sequential customized therapeutic keratectomy (SCTK) in highly aberrated corneas with apical scars consequent to hyperopic excimer laser refractive surgery.
Patients and Methods
In this retrospective study, among the 662 SCTK cases performed between 2000 and 2015 at the Eye Center, Humanitas Clinical and Research Center (Rozzano, Italy), we included all eyes that underwent SCTK for an apical scar after hyperopic refractive surgery with a minimum 12 months of follow-up.
The inclusion criteria for SCTK were prior hyperopic excimer laser correction complicated...