The efficacy and safety of corneal collagen cross-linking in progressive keratoconus with regard to long-term results

Solodkova et al evaluate the efficacy and safety of a modified technique of corneal collagen cross-linking in comparison with the standard approach by the nature changes in clinical and morphological parameters of the cornea in the early and long-term postoperative period. The study included two groups of patients: the group 1 consisted of patients operated on for progressive keratoconus in the classical way of corneal collagen cross-linking--25 individuals (25 eyes), the group 2--patients treated by the modified cross-linking technique--36 individuals (36 eyes). Before and after the procedure in the follow-up of 1,3, 6 and 12 months, all patients underwent an extended ophthalmic examination, including the optical coherence tomography (OCT) of the cornea (Cirrus HD 3000, Carl Zeiss, Germany), the confocal microscopy (Confoscan4, Nidek, Japan). Re-epithelialization of the cornea occurred faster in the group 2. In both investigated groups a significant UCVA increase (from 0.15 0.04 to 0.35 0.07 in the group 1 and 0.13 0.025 to 0.33 0.04 in the group 2) and the BCVA (from 0.3 0.08 to 0.5 0.05 in the group 1 and 0.4 0.04 to 0.87 0.18 in the group 2) was noted in the follow-up period of 6-12 months. After 1 month postoperatively the well-defined linear opacities in the middle and posterior layers of the stroma--the so-called "demarcation lines" or "posterior stromal hazes" appeared during the ophthalmic bio-microscopy as well as in the OCT of cornea in all observed patients. In this period the depth of the «demarcation line» position in the group 1 averaged 252 1 5.0μm, in the group 2--235 10.0μm. The confocal microscopy showed that histomorphological changes were more pronounced in the group 1 within all above-mentioned periods. In the 3-month follow-up in the group 2 a statistically significant reduction in our proposed scoring estimation of all the studied signs, and a maintenance of this trend were detected in the follow-up period after 6 and 12 months, that indicates a more mild and rapid regeneration of cornea after the corneal collagen cross-linking surgery performed according to the modified technique. The endothelial cells density (ECD) remained unchanged in all follow-up periods in both groups. Thus, a manifestation of positive dynamics in the postoperative UCVA, BCVA and the unchanged ECD in all cases allows to consider both options of corneal collagen cross-linking safe, with a comparable clinical efficacy. However, a more pronounced positive dynami