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Intracorneal ring segment implantation in paracentral keratoconus with coincident topographic and coma axis: a comparison between manual and femtosecond laser surgery

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Session Details

Session Title: Presented Poster Session: Cornea III

Venue: Poster Village: Pod 2

First Author: : T.Monteiro PORTUGAL

Co Author(s): :    J. Alfonso   N. Franqueira   F. Faria Correia   J. Merayo-Lloves     

Abstract Details


Intracorneal ring segments (ICRS) implantation is a safe and effective surgical procedure for the treatment of keratoconus. The purpose of this study was to compare the visual, refractive and topographic results of ICRS implantation with manual mechanical technique and femtosecond laser-assisted surgery in a specific phenotype of keratoconus: the paracentral keratoconus with coincident topographic and coma axis.


Ophthalmology Department of Hospital de Braga, Portugal / Escola de Ciências da Saude da Universidade do Minho Fernandez-Vega Ophthalmological Institute, Oviedo, Spain


Prospective study comparing ICRS implantation with manual (group 1) and femtosecond surgery (group 2). The phenotype (paracentral with coincident axis) included the thinnest point located between 0,8 and 1,6 mm of the pupil center and the coma axis between 0° and 30° of the flat topographic axis. The ICRS was centered on the topographic and coma axis; the arc length (120 degrees ± 90 degrees) and the number of segments implanted was based on the Mediphacos nomogram. Parameters evaluated at preoperative and 6 months were: uncorrected (UDVA) and corrected (CDVA) distance visual acuity, manifest refraction, topography and aberrometry.


31 eyes in group 1 and 81 eyes in group 2; no preoperative differences between groups regarding UDVA, BCVA, sphere, refractive and topographic astigmatism, Kmean, K1 and K2 (p>0,05). At 6 months, we observed a significant improvement in UCVA, BCVA, refractive cylinder, topographic cylinder, K1, K2, Kmean and coma in both groups; no significant differences between groups for UCVA, sphere, refractive and topographic astigmatism, K1, K2 and Kmean. Group 2 presented better BCVA and coma at 6 months (p<0,05). In group 1, there were two endothelial perforations, 1 case of decentered implantation and 2 eyes with astigmatism overcorrection.


Ferrara ICRS implantation for the correction of keratoconus in paracentral keratoconus with coincident topographic and coma axis is a safe and effective technique. Both techniques demonstrated to be effective on terms of visual, refractive and topographic parameters. There were no significant differences demonstrated between both surgical techniques, except for final BCVA, which was better in the femtosecond group. Opposite to the manual group, in the femtosecond laser group there were no intra or postoperative complications reported.

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