- Journal of Refractive Surgery
- August 2012 - Volume 28 · Issue 8: 562-566
To compare minimum corneal pachymetry assessment using three measurement methods in eyes before and after corneal collagen cross-linking (CXL) for keratoconus.
Fifty patients (54 eyes) who underwent CXL for keratoconus were evaluated with the Visante (Carl Zeiss Meditec), Pentacam (Oculus Optikgeräte GmbH), and ultrasound pachymetry (USP) (Optikon Pacline) to assess corneal thickness at baseline and 1, 3, 6, and 12 months after treatment.
Using USP, mean thickness was 456 μm at baseline, decreased by approximately 8 μm at 1 month, and then recovered to initial values. The mean difference between Visante and USP was statistically significant, but not clinically significant, and was similar at baseline and after CXL (−1 to −2 μm, P<.05 except for 12 months). Pentacam had similar readings at baseline (−2 μm vs USP), but lower corneal thickness after CXL (−12 to −20 μm throughout follow-up, P<.001). The width of the Bland–Altman 95% agreement interval of Visante and Pentacam with USP was approximately 5 μm and 15 μm, respectively.
Visante pachymetry shows better agreement with USP compared to Pentacam after CXL, which may be due to the inhomogeneous reflectivity of the postoperative cross-linked cornea and possibly altered refractive index and acoustic impedance that may influence the observed differences among techniques.
From the Department of Oto-Neuro-Ophthalmological Surgical Sciences, Eye Clinic, University of Florence, Italy.
The authors have no financial interest in the materials presented herein.
Study concept and design (R.M., I.P.); data collection (I.P., G.V., G.G.); analysis and interpretation of data (U.M.); drafting of the manuscript (I.P.); critical revision of the manuscript (R.M., G.V., G.G., U.M.); statistical expertise (G.V., G.G.); administrative, technical, or material support (R.M.); supervision (U.M.)
Correspondence: Iacopo Paladini, MD, Dept of Oto-Neuro-Ophthalmological Surgical Sciences – Eye Clinic, Viale GB, Morgagni 85, 50134 Florence, Italy. Tel: 39 055 411765; Fax: 39 055 4377749; E-mail: firstname.lastname@example.org
Received: November 03, 2011
Accepted: May 29, 2012
Posted Online: July 13, 2012