Abstract
Purpose: :
To analyze the biomechanical properties of keratoconic corneas before Corneal Cross Linking (CCL), after epithelial removal and after CCL at one and six months follow-up, as measured by the Ocular Response Analyzer (ORA).
Methods: :
Prospective, non randomized clinical controlled study including 24 patients undergoing Riboflavin/UVA CCL and examined by means of ORA and Pentacam pachymetry at each time point in both eyes.
Results: :
Mean corneal hysteresis (CH) changed from 9.68 at baseline, to 10.32 after epithelial removal, to 15.18 immediately after cross linking, to 11.48 at 1 month follow-up and 10.25 six months after CCL, a difference that was not statistically significant from baseline (P>0.05). Mean corneal resistance factor (CRF) changed from 9.05 at baseline, to 9.42 after epithelial removal, to 14.15 immediately after cross linking, to 12.53 at 1 month follow-up and 11.13 six months after CCL, a difference that was not statistically significant from baseline (P>0.05). Comparison of corneal-compensated intraocular pressure (IOPcc) measurements and Goldman correlated intraocular pressure (IOPg) measurements before CCL and at 12 months showed no significant changes (P>0.05).Mean baseline thinnest cornea point (TCP) and total corneal volume (TCV) were 454.80±26.63 µm and 56.17±2.24 mm3 respectively and 419.53±33.36 µm and 55.62±2.50 mm3 at 12 months, a difference that was statistically significant (P<0.05). A significant correlation between TCP and CH was found before CCL and at 6 months (P<0.05). Also, a significant correlation between TCV and both CH and CRF was found before CCL and at 6 months(P<0.05). No significant correlation was found between TCP and IOPcc at 6 months(P>0.05).
Conclusions: :
Intraoperative evaluation showed no significant changes in CH and CRF after epithelial removal and a statistical significant difference in CH and CRF soon after CCL. At 6 months, CCL does not induce any change in intraocular pressure as measured by ORA. CCL induces a significant reduction in corneal thickness and total corneal volume. A significant correlation was found between corneal thickness and CH and CRF in keratoconic eyes before and after CCL.
Keywords: keratoconus • cornea: clinical science • refractive surgery: other technologies