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Paolo Vinciguerra, Renato Ambrosio, Mario Romano, Isaac Ramos, Claudio Azzolini, Silvia Trazza, Riccardo Vinciguerra; Comparison of Biomechanical and Tomographic Data in Subclinical Keratoconus. Invest. Ophthalmol. Vis. Sci. 2013;54(15):1625.
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© ARVO (1962-2015); The Authors (2016-present)
To evaluate the tomographic and biomechanical corneal changes in subclinical keratoconus (KC).
Five patients with very asymmetric KC were retrospectively compared with fellow eyes without tomographic evidences of KC. Tomographic and biomechanical data were respectively obtained with Pentacam and Corvis ST (Oculus Optikgerate GmbH, Wetzlar, Germany). The eyes without tomographic evidences of KC were also compared with five healthy subjects pachymetry- and intra ocular pressure (IOP)-matched. From Pentacam analysis we considered: minimal pachymetry, single and total deviation values(Dv) from Belin-Ambrosio Enhanced Ectasia Display (BAD), and all topometric indexes obtained in the topometric map. From Corvis ST analysis we considered: time (t1-2), length (l1-2) and velocity (v1-2) of first and second applanation, time (tC), peak distance (pC), radius (rC) and deformation amplitude (dC) of highest concavity, IOP and pachymetry
Comparison between KC and the fellow eyes revealed significant differences in single and total Dv evaluated (p<0.05) except for Dv of average pachymetric progression index and deviation of minimum thickness. Similarly topometric values showed a significant difference (p<0.05) between KC and fellow eyes in selected indexes. Corvis ST analysis indicated non significant difference between KC and fellow eyes (p>0.05) in all parameters, showing that fellow eyes had the same pathological biomechanical behavior of the eyes with manifest disease, whereas tomographic analysis didn’t show any significant pathological changes. Comparison between KC patients’ “healthy” eyes and control group showed only scattered significant difference in topometric indexes and in tomographic data in BAD Dv; however the overall total Dv difference was not significant. Conversely biomechanical data revealed significant differences in t1-2 (p<0.01) , v1 (p=0.002), tC (p<0.001), rC (p<0.001), and dC (p<0.001) between KC patients and control group.
Biomechanical analysis with Corvis ST is able to show significant differences between normal eyes and subclinical keratoconus when normal tomographic data show normality or only small abnormalities. In conclusion Corvis ST could be a valid aid in the screening for the risk of ectasia in refractive surgery patients and for early diagnosis of keratoconus.
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