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M. A. Qazi, A. M. Mahmoud, P. S. Kollbaum, M. D. Twa, C. J. Roberts, J. S. Pepose; Application of a Quantitative Method for Identifying Risk for Ectasia After LASIK in Normal, Suspect, and Ectatic Eyes. Invest. Ophthalmol. Vis. Sci. 2010;51(13):2862. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
To compare the Randleman Ectasia Risk Factor (ERF) Score in populations with a clinical diagnosis of normal, suspect keratoconus, and kerectasia, including keratoconus and post-LASIK ectasia.
Eyes were classified as diseased if they had slit-lamp findings characteristic of keratoconus in the study eye (KCN, n=36) or contralateral eye only (KCNfellow, n=10). Keratoconus Suspects (KCS, n=44) had irregular topography but no keratoconic slit-lamp findings in either eye. Normal (NRM, n=32) eyes were selected from a consecutive series of refractive surgery patients with no evidence of ectasia upon follow-up. Preoperative data of eyes that developed ectasia following LASIK (PLE, n=9) were also evaluated. The ERF Score was quantified based upon parameters of age, central pachymetry (CCT), spherical equivalent (SE), calculated residual stromal bed (RSB) assuming a 120 µm flap thickness and ablation of 14 µm/D of SE, and topographic features.
The ERF Score was statistically significantly higher (p<0.01) from NRM (mean 1.67±1.76, range 0-6, median 1) in KCS (3.91±2.25, 1-9, 4), KCNfellow (4.50±2.51, 1-8, 4.5), and KCN (9.08±4.29, 3-16, 8) but not PLE (2.33±1.00, 1-3, 3, p=0.23). In the KCNfellow (2.60±1.43, 1-4, 3) and PLE (2.33±1.00, 1-3, 3) groups, only the topography score was statistically significantly higher (p<0.001) than in NRM (0.39±0.50, 0-1, 0). In preoperative maps of the PLE group, 67% of eyes had a skewed radial axis and 33% had an asymmetric bowtie. Irregular topography (1.82±1.87, 0-4, 1, p<0.001) and younger age (p=0.01) scores were statistically higher in the KCS group compared to NRM.
Application of the Randleman Ectasia after LASIK Risk Score in ectatic and suspicious eyes highlights the importance of topographic analysis in the preoperative assessment of the keratorefractive surgery candidate. Differential weighting of the topography score may enhance the efficacy of ectasia risk analysis. The relative risk of specific topographic features should be further quantified.
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