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  • Demarcation line depth may decrease with ectasia severity and age

    By Jason E. Stahl, MD
    Refractive Mgmt/Intervention

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    This retrospective study in the July issue of the Journal of Refractive Surgery examined variations in demarcation line depth after corneal collagen cross-linking (CXL) for keratoconus and postoperative LASIK ectasia. The results indicate that demarcation line depth may decrease with ectasia severity and age. However, the study failed to find a correlation between demarcation line depth and changes in visual acuity or keratometry at six months.

    This is the first study to investigate correlations with depth of the demarcation line, which represents the transition zone between the cross-linked and untreated cornea and can be seen with confocal microscopy or on OCT. While the significance of the demarcation line remains unproven, it stands to reason that deeper treatments (either in the absolute or relative value) could produce greater corneal reinforcement with benefits in visual and keratometric outcomes.

    The study was a retrospective interventional case series of 40 eyes with keratoconus or postoperative LASIK ectasia treated with riboflavin ultraviolet-A CXL.

    Six months after CXL, mean demarcation line depth was 281.4 ± 53.3 μm. Thinner minimal corneal thickness (P = 0.008), older age (P = 0.001), higher grading of ectasia (for both keratoconus and postoperative LASIK ectasia) (P = 0.044), female sex (P = 0.030), postoperative LASIK ectasia (P = 0.007) and longer duration of disease (P=.023) were correlated with shallower demarcation line depth.

    CXL demarcation line depth was not correlated with change in CDVA (P = 0.325) or change of the steepest keratometry at six months (P = 0.637). Variation in demarcation line depth also showed no correlation with ethnic group, allergic conjunctivitis, family history or the need for corneal swelling for the CXL treatment.

    Forward stepwise multiple linear regression analysis showed that among all preoperative factors, minimal corneal thickness (P = 0.003) and age (P = 0.036) were significantly associated with demarcation line depth.