Medium-to Long-Term Results of Corneal Cross-Linking for Keratoconus Using Phototherapeutic Keratectomy for Epithelial Removal and Partial Stromal Ablation

PURPOSE: To evaluate the medium-to long-term outcomes of corneal cross-linking in treatment of keratoconus using transepithelial phototherapeutic keratectomy (PTK-CXL) for epithelial removal and partial stromal ablation to stabilize the cornea, reduce corneal irregularity, and improve corrected vision. METHODS: Retrospective analysis of 46 keratoconic eyes that underwent PTK-CXL. Corrected distance visual acuity (CDVA), manifest refraction, steep and flat simulated keratometry (Kmax and Kmin), corneal irregularity index (IRI), corneal higher order aberrations (HOAs), epithelial thickness profile, and corneal biomechanical characteristics were evaluated preoperatively and postoperatively. RESULTS: At a mean follow-up time of 21.0 +/- 7.6 months (range: 10 to 43 months) postoperatively, CDVA improved from 0.25 +/- 0.24 to 0.18 +/- 0.22 logMAR (P =.002). CDVA remained unchanged in 32.6% (15 eyes) and 56.5% (26 eyes) gained up to five Snellen lines of CDVA, whereas 6.5% (3 eyes) lost two or more lines of CDVA, respectively. Postoperatively, flattening of Kmax from 50.58 +/- 5.26 to 48.96 +/- 4.00 diopters (D) and Kmin from 45.80 +/- 3.11 to 44.77 +/- 2.63 D (P < .001), reduction of IRI from 49.7 +/- 24.5 to 43.4 +/- 21.4 mu m (P =.002), decrease of root mean square HOAs (at 5-mm diameter) from 2.66 +/- 1.31 to 2.37 +/- 1.37 mu m (P =.037), and slight thickening of corneal epithelium were registered, whereas most of the corneal biomechanical measurements did not show statistically significant change. Two eyes demonstrated slight topographic regression. CONCLUSIONS: PTK-CXL seems to be effective in arresting the progression of keratoconus, improving CDVA, flattening the cornea, regularizing corneal surface, and reducing corneal HOAs.