Changes In Ocular Higher Order Aberrations After Corneal Collagen Cross-Linking For Keratoconus

 The aim of the study is to assess the changes in ocular higher order aberrations (HOAs) after corneal collagen cross linking (CXL) for keratoconus (KC). 

 Nour El Ain Eye Hospital, Tanta, Egypt 

 This is a prospective interventional study that included 30 eyes with confirmed KCN. Baseline evaluation included: UDVA and BSCVA using logMAR notation, manifest refrative spherical equivalent (MRSE), slit lamp examination, dilated fundus exam, corneal topography using Orbscan IIZ and wavefront aberrometry using Zywave II. Cross-linking procedure was performed according to ‘Dresden protocol’ through a 30-minutes exposure to 370 nm UVA with an irradiance of 3 mW/cm2. All patients had comprehensive ophthalmic evaluation after six months with special attention to: visual acuity assessment (UDVA, BSCVA and MSE), slit lamp examination, corneal topography changes and wavefront aberrometry. 

 The mean age was 25.5±5.84 (20:31) years. There was a significant decrease in the corneal thickness from preoperative 493.2± 24.17µ to 486.7±24.26µ (P<0.05), and a significant decrease in K max from 47.4±1.17D to 46.1±1.17D after 6 months (P<0.05). Preoperative BSCVA was 0.00:0.5 logMAR (median 0.3), at 6 months was 0.1:1.00 logMAR (median 0.2) (P <0.05). Preoperative MRSE was -7.25: -0.5D (median -2.85D) and at 6 months was -6.25: -0.5D (median - 2.125D) (P<0.05). A significant correlation was found at 6 months between changes in both BSCVA and: K max (P<0.001), corneal thickness (P<0.05), vertical coma (P<0.001) and trefoil (P<0.001). 

 The findings of our study demonstrated an improvements in HOA using the Zywave Aberrometer after CXL in keratoconic eyes. Multivariable analysis found changes in total, vertical and coma aberrations that were significantly correlated with postoperative improvement in BSCVA. Thus, improvement in HOA profile after CXL is one of the explanations of improvement in visual function after CXL in keratoconic eyes.