Continuous Light Accelerated Crosslinking Matches Stability of Pulsed Light

A longer duration continuous light crosslinking protocol has comparable efficacy to an accelerated pulsed light crosslinking protocol in terms of postoperative stability and corneal tissue penetration.

Continuous light accelerated crosslinking (cl-CXL) has similar postoperative stability and corneal penetrating capabilities to pulsed light accelerated crosslinking (pl-CXL), according to findings published in Clinical Ophthalmology.

Researchers conducted a retrospective study to compare 2 accelerated crosslinking protocols in the management of keratoconus (KC). The study included 2 groups of patients with mild-moderate progressive KC: group 1 was comprised of 103 eyes that received pulsed light accelerated crosslinking at a power of 30 mW/cm2 with an irradiation time of 4 minutes; and group 2 included 87 eyes that received continuous light accelerated crosslinking at a power of 12 mW/cm2 with an irradiation time of 10 minutes.

Using anterior segment optical coherence tomography (AS-OCT), the researchers compared recordings of the central and peripheral demarcation line depths (DD), and the maximum (DDmax) and minimum (DDmin) DD, between the 2 study groups 1 month after treatment protocol.

Evaluation of treatment stability was performed pre and postoperatively (1 year following surgery) by comparing the refractive and keratometric outcomes in both groups.

The study found no statistically significant differences in the preoperative corneal thickness (minimum and central) and the epithelial thickness measurements between the 2 groups. However, the patients who underwent pulsed light accelerated crosslinking had slightly larger central DD (223.4±62.3 µm), DDmax (240.4±61.8 µm), and DDmin (201±54 µm) than the patients who underwent continuous light accelerated crosslinking (221.8±37 µm, 229.1±38.4 µm, and 212±37.2 µm, respectively).

It is noteworthy that the DD cannot be considered as a sole reliable parameter for the effectiveness of CXL protocols.

Differences in the subjective refraction and the average and maximum keratometry, denoting visual, refractive, and keratometric stability, pre- and postoperatively, was also statistically insignificant between the 2 accelerated crosslinking protocols.

“It is noteworthy that the DD cannot be considered as a sole reliable parameter for the effectiveness of CXL protocols,” the researchers explain. “Hence, we also compared the pre and postoperative visual, refractive, and keratometric performances, which indicated
stability in both groups.”

Study limitations include those inherent to its retrospective nature; and possible confounding of data due to the use of both eyes in some patients. A strength of this study involves its large sample size which confirmed previous findings regarding the reliability of AS-OCT to measure DD following accelerated crosslinking.


Yousif MO, Elkitkat RS, Alaarag NA, Seleet MM, Soliman AH. Comparison between pulsed and continuous accelerated corneal cross-linking protocols. Clin Ophthalmol. 2023;17:1407-1413. doi:10.2147/opth.s409178