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Importance of the morphological classification of keratoconus in INTACS-SK implantation

Poster Details

First Author: P.Rodrigues PORTUGAL

Co Author(s):    M. Marques   S. Alves   H. Nogueira              

Abstract Details


Ferrara type rings current approaches take into account a morphological classification that includes coma, in which F1-3 are paracentral cones (F1 with astigmatism coincident with coma, F2 with astigmatism oblique to coma and F3 with astigmatism perpendicular to coma) and F4-5 are central cones. Improved results are reported using this approach. INTACS-SK are effective but have less variety of thickness or curvature and planning includes fewer factors. Our purpose is to analyze clinical and topographic characteristics of INTACS-SK implantation in keratoconus patients and determine its influence in the final result.


Instituto de Oftalmologia Dr. Gama Pinto, Lisboa


Cases of successful INTACS-SK implantation for keratoconus between 2015 and 2017 were retrospectively analyzed, namely in terms of pre and post-operative best corrected visual acuity (BCVA), refraction and topographic characteristics. Keratocones were also classified morphologically. INTACS-SK were implanted by the same surgical team according to the manufacturer nomogram. Linear regression analyses were performed in order to clarify the predictive power of topographical variables, such as average corneal curvature (Kmed), steepest curvature (Kmax) and coma. Group comparison according to the morphological classification was also performed.


50 eyes were included. Pre-operatively, BCVA was 0.53±0.18, spherical equivalent was -4.91D±3.41, astigmatism was 5.30D±2.27, Kmed was 46.95D±1.97 and Kmax was 48.47D±2.12. Morphologically, 39.3% of the cases were classified as F4, 25% as F2, and 17.9% as F3 and F1. Post-operatively, BCVA was 0.6±0.22, spherical equivalent was -2.29D±3.90, astigmatism was 3.63D±1.52, Kmed was 43.54D±2.17 and Kmax was 44.73D±2.25. These values were significantly different from pre-op values. The only predictive variable of final BCVA was initial BCVA (r2=0.33). Morphological classification showed differences in final BCVA, with F4 presenting worse results (BCVA=0.49).


INTACS-SK are effective in improving BCVA and lowering corneal curvature and refraction values. The best predictor of final BCVA was initial BCVA, confirming that earlier stages of keratoconus have the best results. Keratoconus morphological classification was also important, as central keratoconus was associated with worse results. Coma did not show a significant influence in visual acuity. Keratoconus patients have an irregular cornea which causes visual dysfunction that is hard to measure and predict. Improved nomograms are necessary to achieve the best results, but early diagnosis and control of the disease is still the best way to improve the outcome.

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