This study investigates the outcomes of patients who underwent photorefractive keratectomy (PRK) followed immediately by standard 30-minute corneal crosslinking (CXL) for keratoconus.
Study design
This retrospective nonrandomized study evaluated the outcomes of 26 keratoconic eyes of 16 patients who underwent topography-guided PRK with the Schwind Amaris 500 immediately followed by Dresden protocol corneal crosslinking. All patients were 21 years or older, and had a predicted residual stromal bed of greater than 400 microns. Mitomycin C 0.02% was applied for 20 to 30 seconds, and a bandage contact lens was placed for 1 week. Topography, tomography, UDVA, CDVA and a slit lamp exam were performed at every follow-up visit for an average of 32 months.
Outcomes
Both eyes of 1 patient exhibited delayed re-epithelialization, while another patient lost CDVA in 1 eye due to a deep haze. Overall, mean UDVA improved with decreases in coma and spherical aberration. Mean CDVA, however, worsened significantly from baseline values (0.15 vs. 0.07 logMAR; P=0.006). Overall, 84.6% of eyes developed at least grade 1 haze, while 27% of eyes lost 2 lines or more of CDVA. Patients with a history of atopy had the highest risk of CDVA loss.
Limitations
This study is retrospective in nature and uses a laser that is not available in the United States. In addition, the technique for removing the epithelium, optical zone and treatment depth all varied by patient. Finally, many of the patients had significant ablation depths (>50 microns) which has been shown to increase the risk of haze, and the authors did not stratify this risk of haze by ablation depth.
Clinical significance
Performing same-day CXL and topography-guided PRK has been shown to increase the risk of haze, yet it improves the convenience for patients undergoing the procedures. Studies have provided conflicting evidence as to whether this risk is significant enough to discourage this approach. Based on this study as well as other reports, appropriate counseling for patients of the potential risks of same day topography-guided PRK and CXL is important, and the option of sequential procedures should be considered, especially in higher risk patients.