Comparison of Continuous versus Pulsed Mode in Accelerated Corneal Collagen Cross-linking for Keratoconus

To compare efficacy and safety between the two modes of energy delivery-pulsed and continuous, in accelerated corneal collagen cross-linking (KXL) to stop the keratoconus advancement through topographical, visual, and refractive endpoints.

It was a prospective, comparative, randomized, interventional trial. Patients with bilateral progressive keratoconus were subjected to pulsed mode KXL (P-KXL) in the right and continuous mode KXL (C-KXL) treatment in the left eye. In both methods, additional supplemental oxygen was delivered to corneal surface using a nasal cannula connected to an oxygen supply. Uncorrected distance visual acuity (UDVA) and corrected distance visual acuity, posttreatment manifest spherical equivalent and astigmatism, and corneal topography were studied. The deformation amplitude index (DAI) was measured by Corvis-ST. Postoperative follow-up was done.

One hundred eyes of 50 patients underwent P-KXL in the right eye and C-KXL in the left eye. The average follow-up was 12.1 ± 1.2 months. At 1 year posttreatment, the UDVA had a mean change of 0.11 ± 0.14 logMAR in P-KXL and 0.18 ± 0.14 logMAR in C-KXL groups. The line of demarcation was observed at 251.13 ± 18.28 μ and 245.28 ± 28.26 μ deep, respectively, in P-KXL- and C-KXL-treated eyes at 6 months' follow-up. The DAI as measured by Corvis-ST showed a significant decrease from pretreatment values of 1.12 ± 0.13 mm to 0.84 ± 0.14 mm (P < 0.01) in P-KXL eyes and from 1.04 ± 0.14 mm to 0.85 ± 0.15 mm (P = 0.03) in C-KXL eyes. Both the groups did not show any statistically significant endothelial cell loss posttreatment.

C-KXL can give similar functional outcomes as P-KXL with the help of supplemental oxygen delivery with the added advantage of a shortened procedure time in comparison to pulsed mode.