Prospective two‐year study of clinical outcomes following epithelium‐off pulsed versus continuous accelerated corneal crosslinking for keratoconus

Abstract

Importance Keratoconus is a debilitating condition with a disproportionately high impact on health resources and vision‐specific quality of life. Background This study aimed to compare 2‐year outcomes of epithelium‐off pulsed (p‐ACXL) and epithelium‐off continuous (c‐ACXL) accelerated corneal crosslinking in progressive keratoconus. Design Prospective, interventional case series. Participants Eighty eyes of 80 patients were included. Methods The visual, refractive and tomographic results of the two crosslinking protocols were compared. Main Outcome Measures Uncorrected distance visual acuity, corrected distance visual acuity (CDVA), manifest refraction spherical equivalent (MRSE) and maximum keratometry (KMAX) on corneal tomography assessment. Results The mean patient age was 22.51 ± 6.12 years (SD) and 22.08 ± 5.72 years in the p‐ACXL and c‐ACXL groups, respectively. The mean CDVA significantly improved from 0.30 ± 0.16 logMAR at baseline to 0.23 ± 0.17 logMAR at 24 months (P = .04) in the p‐ACXL group and from 0.36 ± 0.22 logMAR to 0.26 ± 0.27 logMAR (P = .02) in the c‐ACXL group. The mean induced change in MRSE (+1.79 ± 2.30 D vs +0.27 ± 3.19 D, P = .04) and KMAX (−1.75 ± 1.80 D vs −0.39 ± 1.95 D, P = .04) were superior in the c‐ACXL group compared to the p‐ACXL group at 24 months. No complications were encountered. Conclusions and Relevance In this prospective study, both p‐ACXL and c‐ACXL treatments were safe methods to halt the progression of keratoconus within a follow‐up period of 24 months. c‐ACXL appeared to offer superior refractive and tomographic outcomes when compared to p‐ACXL but this did not translate into better visual outcomes.

Keratoconus treatment: The journey has just begun

“…In their paper, Ziaei et al found that the continuous A‐CXL cohort achieved a greater mean reduction in both manifest refraction and maximum keratometry compared to the patients who received pulsed CXL. The difference was statistically significant albeit there remained some variation in the outcomes . The impact on best‐corrected visual acuity was positive for both groups; however, this did not appear to translate into a clinically significant change over the course of extended follow‐up matching existing meta‐analyses .…”

“…This is significant because the risks of additional retreatment on long‐term corneal health are largely unknown. Our lack of understanding of the impact of surgical variables is readily identified by Ziaei et al and was confirmed recently in a further study by Lang et al They found little correlation between the change in measured variables and corrected vision . Indeed, we cannot be sure whether long‐term evaluation of keratoconic treatment outcomes reflects the impact of the treatment or simply the influence of the regular age‐related corneal stiffening process .…”

“…Researchers have introduced a myriad of alternatives aimed at increasing comfort, reducing surgery time and further minimizing complications; however, outcomes from these newer protocols have varied. This month, Ziaei et al present a prospective study of 80 eyes comparing pulsed vs continuous accelerated CXL (A‐CXL) at 2 years . Both cohorts were prepared by removing the epithelium prior to the application of riboflavin and UV‐A light.…”

“…A‐CXL reduces procedure time by utilizing the Bunsen‐Roscoe law of photochemical reciprocity. Furthermore, pulsed delivery of UV‐A light is suggested to allow greater diffusion of oxygen into the corneal stroma facilitating enhanced release of singlet oxygen and a more effective CXL process . Although easier for the patient, clinical outcomes of A‐CXL in the previously published literature suggest less overall impact on improving best‐corrected visual acuity, albeit keratometry, safety and progression outcomes would appear to remain relatively similar to standard CXL eyes .…”

Comparison of corneal biomechanical properties following penetrating keratoplasty and deep anterior lamellar keratoplasty for keratoconus

“…Initially, visual acuity can be corrected with spectacles or contact lenses. Corneal cross‐linking utilizes a photochemical reaction between the riboflavin and ultraviolet A (UV‐A) in the corneal stroma and has been reported to arrest the progression of the disease, but in cases of advanced keratoconus, corneal transplantation may be required to improve vision . Penetrating keratoplasty (PKP) was the earliest transplant technique used to treat keratoconus, and remains the mainstay for managing late‐stage disease in many countries .…”