Keratoconus is a corneal ectasia with progressing corneal thinning and scarring ultimately leading to visual deterioration. Collagen cross-links have been identified early as an important factor to limit disease progression.
1 Over the last 10 years, cross-linking (CXL) with riboflavin and UV-A has evolved to be a valid treatment option for progressive keratoconus. Wollensak and Spoerl
2 first introduced CXL with the standard Dresden protocol with 30 minutes UV irradiation and 3 mW/cm
2 UV intensity as an effective treatment for increasing corneal rigidity and thus halting progression of keratoconus. Since then, several studies have been published on the safety of the standard Dresden protocol
3 and its long-term effectiveness.
4,5 Furthermore, the application has been extended from the adult setting to the pediatric population (<18 years).
6,7 With evolving technical advances, commercially available UV light sources have been developed, making CXL more efficient with shorter UV exposure times, higher UV intensities, and pulsed light compared with continuous light settings.
8 Various accelerated CXL protocols have been described and its effect on biomechanical properties on porcine corneas stated as equal to the standard protocol.
9 Yet, ex vivo studies also suggest a distinction between various accelerated CXL protocols by providing evidence for a drop in efficiency with increased UV illumination intensity while maintaining equal surface energy.
9 Clinical studies have been recently published comparing the standard protocol with a continuous light accelerated CXL protocol with 3 minutes UV irradiation time and 30 mW/cm
2 UV intensity in a total of 48 eyes, showing no difference in the occurrence rate of the demarcation line and corneal topography at 1-year follow-up.
10 Elbaz et al.
11 recently published a comparable study of 16 eyes showing effective stabilization of topographic parameters 12 months after accelerated CXL. On the other hand, further studies observe a decreased depth of the demarcation line (DLD) after using the rapid CXL protocol with 10 minutes of irradiation time and 9 mW/cm
2, suggesting a reduced effectiveness.
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