The Impact of Standard Cross-Linking on the Corneal Optical Density-Age Relationship in Keratoconus After Mechanical Stripping of the Epithelium

Background: To determine if cross-linking (CXL) treatment modifies any pre-existing association between corneal optical density (COD) and age in keratoconus free of corneal scarring.Methods: COD was monitored in two groups (i) before and after standard CXL treatment for keratoconus (de-epithelization with a crescent blade, n = 69 eyes) and (ii) age/gender-matched cases without any signs of keratoconus (n = 24 eyes). Seven different markers of COD were quantified using a 0-100 grey scale, supplied with Pentacam (TM) software.Results: Mean age (+/- sd, range) in Group I (19 females and 50 males) was 24.2 years (+/- 7.2, 11-44) and in Group II (9 females and 15 males), it was 24.7 years (+/- 7.6, 17-45). COD over the apex and along the depth of the cornea (y, arbitrary scale units) was associated with age (x, in years) in Group I at preop (y = 0.08x + 13.12, rs = 0.350 and p=0.003), at 12 months postop (y = 0.08x + 15.15, rs = 0.295 and p=0.014) and in Group II, at the start (y = 0.16x + 11.28, rs = 0.474 and p=0.019) and 12 months later (y = 0.24x + 8.63, rs = 0.600 and p=0.002). The change in COD following CXL was significantly associated with the preop value.Conclusion: CXL initially breaks down the pre-existing relationship between COD and age. This is re-established by 12 months postop. The CXL induced change in COD depends on the preop value but not on the patient's age.