Wave Front–Guided Photorefractive Keratectomy Using a High-Resolution Aberrometer After Corneal Collagen Cross-Linking in Keratoconus

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Abstract

Purpose:

To evaluate the clinical outcomes of wave front–guided (WFG) photorefractive keratectomy (PRK) using a high-definition aberrometer in corneas with keratoconus at least 1 year after corneal collagen cross-linking (CXL).

Methods:

Prospective uncontrolled interventional case series study including a total of 34 consecutive eyes of 25 patients with keratoconus previously treated with CXL. All cases underwent WFG PRK using the VISX STAR S4 IR excimer laser and the iDesign system. All eyes had keratoconus grade I or II according to the Amsler–Krumeich classification. Visual, refractive, and ocular aberrometric outcomes were evaluated during a 12-month follow-up. Astigmatic changes were analyzed with the Alpins vector method.

Results:

A significant improvement was observed in the uncorrected and corrected distance visual acuities (P < 0.001). The mean efficacy and safety indices at 12 months postoperatively were 1.58 ± 1.11 and 1.96 ± 1.52, respectively. Manifest sphere and cylinder were reduced significantly (P < 0.001), with 76.5% of the eyes having a spherical equivalent within ±1.00 D at 12 months postoperatively. The mean difference vector and magnitude of error were 1.06 ± 0.92 and 0.43 ± 0.86 D, respectively. Some corneal irregularity indices were reduced significantly with surgery (P ≤ 0.005) as well as the level of ocular higher order aberrations, primary coma, and trefoil (P < 0.001).

Conclusions:

Sequential WFG PRK using the iDesign system and the STAR S4 IR excimer laser after CXL is an effective option to correct the spherocylindrical error and to minimize the level of higher order aberrations in mild and moderate keratoconus if the maximum intended ablation depth does not exceed 15% of the minimal corneal thickness.

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