Hyperopic correction: clinical validation with epithelium-on and epithelium-off protocols, using variable fluence and topographically customized collagen corneal crosslinking

Anastasios John Kanellopoulos, George Asimellis, Anastasios John Kanellopoulos, George Asimellis

Abstract

Purpose: To report novel application of topographically-customized collagen crosslinking aiming to achieve hyperopic refractive changes. Two approaches were evaluated, one based on epithelium-off and one based on epithelium-on (transepithelial).

Methods: A peripheral annular-shaped topographically customizable design was employed for high-fluence ultraviolet (UV)-A irradiation aiming to achieve hyperopic refractive changes. A total of ten eyes were involved in this study. In group-A (five eyes), a customizable ring pattern was employed to debride the epithelium by excimer laser ablation, while in group-B (also five eyes), the epithelium remained intact. In both groups, specially formulated riboflavin solutions were applied. Visual acuity, cornea clarity, keratometry, topography, and pachymetry with a multitude of modalities, as well as endothelial cell counts were evaluated.

Results: One year postoperatively, the following changes have been noted: in group-A, average uncorrected distance visual acuity changed from 20/63 to 20/40. A mean hyperopic refractive increase of +0.75 D was achieved. There was some mild reduction in the epithelial thickness. In group-B, average uncorrected distance visual acuity changed from 20/70 to 20/50. A mean hyperopic refractive increase of +0.85 D was achieved. Epithelial thickness returned to slightly reduced levels (compared to baseline) in group-A, whereas to slightly increased levels in group-B.

Conclusion: We introduce herein the novel application of a topographically-customizable collagen crosslinking to achieve a hyperopic refractive effect. This novel technique may be applied either with epithelial removal, offering a more stable result or with a non-ablative and non-incisional approach, offering a minimally invasive alternative.

Keywords: CXL hyperopic correction; CXL presbyopic correction; KXL II; PiXL; epi-on and epi-off CXL; high-fluence cross linking; topography customizable crosslinking.

Figures

Figure 1
Figure 1
The KXL II device (Avedro Inc., Waltham, MA, USA) shown with the customizable annular pattern designed in the main control screen and the steerable ultraviolet-A head unit with the built-in tracker camera image.
Figure 2
Figure 2
Customized profile employed in the hyperopic treatment. Notes: (A) Top view of the customized corneal crosslinking (CXL) pattern utilized; (B) cross-sectional schematic proposed mechanism of CXL action; (C) cross-sectional schematic of proposed hyperopic CXL effect. The ring had an inner radius of 6 mm and outer 9 mm. Exposure time was 13 minutes and 20 seconds; energy was 12.0 J/cm2.
Figure 3
Figure 3
Placido disk topography sagittal curvature maps (diameter 9 mm) depicting hyperopic refractive changes. Notes: 1: 6 months postoperatively; 2: preoperative. (A) Example from group-A, PTK; (B) example from group-B, transepithelial. Abbreviation: PTK, laser-debridement epithelial removal.
Figure 4
Figure 4
Scheimpflug imaging data showing comparison of 6 months postoperative data (A) versus preoperative (B), as well as the difference A–B (C), indicating the hyperopic refractive changes. Notes: (A) Example from group-A, PTK; (B) example from group-B, transepithelial; (C) difference of A–B. Abbreviation: PTK, laser-debridement epithelial removal.
Figure 5
Figure 5
Anterior-segment OCT imaging pachymetry maps for cornea (left) and corneal epithelium (right) covering the center 6 mm diameter area. Notes: Top, preoperative, middle, 1 month postoperatively, and bottom, 6 months postoperatively. (A) Example from group-A, PTK. Corneal and corneal epithelial thickness imaging maps. (B) Example from group-B, transepithelial. Corneal and corneal epithelial thickness imaging maps. Abbreviations: OCT, optical coherence tomography; PTK, laser-debridement epithelial removal.

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