Central versus paracentral cone location and outcomes of cross-linking in keratoconus patients
First Author: M.Mimouni CANADA
Co Author(s): N. Sorkin T. Trinh W. Hatch N. Singal
To compare outcomes one year after corneal crosslinking (CXL) keratoconus eyes with central cones to those with paracentral cones.
A post-hoc analysis of data collected pre operatively and at one year after CXL only in progressive keratonic eyes from a prospective study conducted between 2013 and 2015 at the Kensington Eye Institute, Toronto, Canada.
Eyes with PMD, postoperative ectasia, apical scarring and peripheral cones (>5mm) cones were excluded. Preoperative manifest refraction, corneal cylinder, maximal keratometry (Kmax), central and minimal corneal thickness and coma were included in the analysis. Central, paracentral and peripheral cones were defined as cones within the central 3mm, between 3-5mm and beyond 5mm, respectively. The primary outcome measures were change in best spectacle corrected visual acuity (BSCVA) and Kmax. Secondary outcomes included change in refractive error, coma and corneal thickness indices.
Three-hundred-fourteen eyes of 314 patients with a mean age of 27.5±7.7 years were included. The central cone group was younger (26.6±7.1 versus 32.4±9.2 years, p<0.001) and had lower corneal astigmatism (3.3±2.0D versus 4.0±1.9D, p=0.03). At one year, after adjusting for baseline characteristics, the central cone group showed a greater reduction in spherical equivalent (1.27±0.60D, p=0.04) and more improvement in BSCVA (0.08±0.02 logMAR, p<0.001). There was no significant difference in progression between groups (ΔKmax>1D, 19.4% versus 10.9%, p=0.13). Within group analyses revealed a reduction in spherical equivalent and BCSVA improvement of almost one line in the central group (p<0.001 for both).
This large-scale study of keratoconus eyes one year after CXL indicates that compared to those with paracentral cones, central cones have on average almost one-line improvement in BCSVA and 1.27D reduction in myopia.