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Clinical comparison between the use of 5 mm and 6 mm diameter intrastromal ring segments for treating corneal ectasia

Poster Details

First Author: H.Noguera SPAIN

Co Author(s):    J. Alberdi Alberdi   V. Diaz Lacalle   I. Gomez Lorente   M. Canillas Argui   V. Ramos C   R. Jimenez Cocco

Abstract Details


To compare clinical features and complications occurred alter the implantation of 5 mm diameter (Ferrara Ring® ) and 6 mm diameter (Keraring ®, Mediphacos) intrastromal corneal ring segments for treating different types of corneal ectasia, such as keratoconus, pellucid marginal degeneration and post-LASIK ectasia.


Due to the recent scientific articles published defending the use of 6 mm diameter rings instead of those of 5 mm; we decided to compare the clinical results and number of complications occurred after the mechanic implantation of these intrastromal segments.


We show a retrospective study of a series of 36 intrastromal corneal ring segments implanted in 23 eyes over the last 30 months. A total of 26 Ferrara Rings ® with a diameter of 5 mm and 10 Kerarings ® wich had 6 mm of diameter were analyzed. Both groups have been compared in terms of uncorrected and best corrected visual acuity, depth of implantation, mean K-values and complications occurred since the implantation. The procedures were always performed by the same surgeon. Different methods were used to analyze all clinical features, such as the Pentacam®, the application for Anterior Segment Imaging from the Cirrus HD-OCT® and from the Optovue® devices; among others.


After implantation mean K-values and both uncorrected and best-corrected visual acuity improved significantly in both groups. We found that due to the use of mechanic implantation of the segments, most of the rings were introduced too superficial. This had poor significant effects on the 5 mm group (7 % of segments extruded) but this percentage raised up to 30 % in the 6 mm group. In addition, we observed that 11 % of the segments had to be removed in the 5 mm group due to different complications such as corneal abscess, extrusion, intolerance, etc.; in comparison with the 6 mm group in which 60% of the intrastromal corneal rings had to be explanted. It is important to highlight that this group has less number of cases, which may influence these results. In two cases complementary corneal procedures were needed, such as cross-linking or penetrating keratoplasty.


In our experience, when properly placed, both types of intrastromal corneal ring segments show a good clinical profile in order to ease further optical correction in cases of corneal ectasia. However, when the 6 mm diameter rings are not placed deep enough, the number of complications is higher and significantly more segments require explantation. FINANCIAL DISCLOSURE?: No

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