This study compared the 3-year outcomes of iontophoretic transepithelial corneal crosslinking (I-ON CXL) vs epithelium-off CXL in pediatric patients with keratoconus.

Study design

This study included 40 affected eyes from 28 pediatric patients with keratoconus, ranging in age from 9 to 18 years. Twenty eyes of 15 patients received the I-ON protocol, while 20 eyes of 13 patients underwent epi-off CXL. The authors evaluated the mean corrected distance visual acuity, spherical equivalent, maximum keratometry (Kmax), posterior elevation of the thinnest point, and thickness of the thinnest point.

Outcomes

There was a statistically significant improvement in corrected distance visual acuity (from 0.18 to 0.10 logMAR; P = 0.03) in the epi­-off CXL group, but not in the I-ON group. There were no significant improvements in spherical equivalent or posterior elevation of the thinnest point in either group. The average Kmax increased significantly from baseline while the thinnest pachymetry decreased significantly in both groups at 36 months.

Keratoconus progression (defined by an increase in Kmax of the anterior corneal surface of at least 1.00 D) occurred in 25% of epi-off and 50% of I-ON CXL patients over the 3-year period. Kmax value in I-ON, and cone location in both groups, seemed to be factors influencing the disease progression.

Limitations

Contrary to the difference in efficacy between groups, the I-ON group reported less discomfort than their epi-off counterparts. After epi-off CXL, all patients reported significant discomfort during the first 7 days after surgery. Adverse effects, such as corneal haze, occurred in 4 eyes (20%) and resolved without sequelae in all cases. After I-ON CXL, no patients suffered significant discomfort, however 9 eyes (45%) exhibited superficial punctate keratitis that resolved within 7 days.

Clinical significance

In pediatric patients, standard epi-off CXL halted keratoconus progression in 75% of eyes during the 3 years after treatment. By contrast, I-ON CXL seemed to slow down keratoconus progression in 50% of eyes, mainly in those with highest Kmax and paracentral cone.