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From London Vision Clinic, London, United Kingdom (DZR, MG, TJA, GIC); Columbia University Medical Center, New York, New York (DZR); Centre Hospitalier National d'Ophtalmologie, Paris, France (DZR); and the Biomedical Sciences Research Institute, University of Ulster, Coleraine, United Kingdom (DZR, TJA).
Dr. Reinstein is a consultant for Carl Zeiss Meditec AG, Jena, Germany, and has a proprietary interest in the Artemis technology (ArcScan Inc., Morrison, Colorado) through patents administered by the Center for Technology Licensing at Cornell University, Ithaca, New York. The remaining authors have no proprietary or financial interest in the materials presented herein.
Excimer lasers have been used as a corneal treatment for hyperopia since Dausch et al. 1 first reported the results of photorefractive keratectomy for hyperopia up to +7.50 diopters (D) in 1993 using the MEL 60 excimer laser (Carl Zeiss Meditec, Jena, Germany). Although earlier generation lasers and ablation profiles were associated with substantial regression, 2-4 undercorrection, 5,6 and loss of corrected distance visual acuity (CDVA), 1,3,4,6 current generation technology employing larger optical zone and transition zone size has led to improved outcomes, 7-15 significantly reducing the induction of higher order aberrations and improving optical quality and postoperative stability. Results have also considerably improved since the earlier days of hyperopic corneal treatment by changing the protocol for ablation centration from the entrance pupil center to the corneal vertex 16 or coaxially sighted corneal light reflex (CSCLR). 17 The past 10 years have seen an increased number of publications demonstrating safe and effective results in the corneal treatment of hyperopia, 12,14,18-20 reflecting how this modality has become a standard option.
It has been known for a long time in observing the progression of keratoconus in its more advanced stages that when the cornea attains high central curvature, this can lead to epithelial instability and breakdown with apical scarring, commonly described as 'apical syndrome.' The in vivo epithelial thickness profile of both the normal cornea 21,22 and that of the keratoconic cornea 23,24 were first characterized by our group using Artemis very high-frequency digital ultrasound (VHFDU) scanning technology (ArcScan Inc., Morrison, CO). 21,25 In keratoconus, the epithelium exhibits a donut-shaped thickness profile with the thinnest epithelium overlying the steepest part of the cone, with an annulus of thickened epithelium surrounding the...