Reassessment of the Clinical Significance of the Demarcation Line in the Corneal Stroma in Crosslinking

Abstract

Purpose: To consider the clinical significance and features of the formation of a demarcation line in the corneal stroma with various methods of corneal crosslinking. Materials and Methods: Literature data on the evaluation of the effectiveness of various methods of crosslinking by the demarcation line in the corneal stroma were analyzed. The formation of a demarcation line during prophylactic and therapeutic excimer laser crosslinking was studied after various photorefractive operations, keratoconus and other pathologies of the cornea (168 operations). Results: With various methods of crosslinking, including prophylactic and therapeutic excimer laser corneal crosslinking, the depth of the demarcation line in the stroma varied from 1/3 to 2/3 of the corneal thickness. It was noted that the saturation of the corneal stroma with a 0.25% solution of riboflavin is accompanied by a large increasing effect of the optical density in the stroma above the demarcation line at a shallower depth of its occurrence. The severity of the aseptic inflammatory reaction after corneal crosslinking affected the optical density, shape, intensity, and depth of the demarcation line in the stroma. In some cases, the formation of a demarcation line in the stroma was noted when the stroma was saturated with riboflavin immediately after refractive keratoablation without additional UV irradiation. The demarcation line in the stroma was revealed during inflammatory processes in the corneal stroma without the participation of riboflavin and its activation by UV radiation.  The study showed that the assessment of corneal crosslinking by the depth of the demarcation line is not an indicator of the photochemical process and the number of crosslinks formed in the corneal stroma. Conclusion: Based on the severity, shape and depth of the demarcation line, it is not possible to judge the density of crosslinks in the corneal stroma, which predetermine its strength properties after one or another method of corneal crosslinking.