Corneal demarcation line indicates depth of cross-linking treatment

A stromal demarcation line can be seen in corneas after corneal collagen cross-linking for the treatment of keratoconus, indicating the effective depth of the treatment, researchers in Switzerland have found.

Theo Seiler, MD, PhD, and colleagues at the University of Zurich pioneered the technique of corneal collagen cross-linking using applications of ultraviolet light and riboflavin. Now Dr. Seiler and Farhad Hafezi, MD, have identified a biomicroscopically detectable demarcation line that shows the transition zone between treated and untreated cornea.

"To date, the effectiveness of treatment could be monitored only indirectly by postoperative follow-up corneal topographies or using corneal confocal microscopy," the researchers said.

Corneal collagen cross-linking was performed on 16 patients with progressive keratoconus. At 2 weeks after treatment, 14 of 16 eyes had thin stromal demarcation lines visible via biomicroscopy at an approximate depth of 300 µm over the whole cornea, according to Drs. Seiler and Hafezi.

The line may result from differences in the refractive index or reflection properties of untreated and cross-linked corneal stroma, and it represents an effective tool to measure the depth of cross-linking, they said.

The study is published in the October issue of Cornea.