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Results of intracorneal ring segment implantation for keratoconus with non-coincident topographic and coma axis

Poster Details

First Author: I. Martins De Almeida PORTUGAL

Co Author(s):    J. Jesus   M. Matias   J. Chibante              

Abstract Details


To evaluate visual and topographic results of the implantation of Ferrara-type intrastromal corneal ring segments (ICRS) for the refractive correction of paracentral keratoconus (KC) with non-coincident topographic and coma axis (duck-like phenotype).


Centro Hospitalar Entre o Douro e Vouga, Santa Maria da Feira, Portugal


Outcome measures included Snellen Uncorrected (UDVA) and best corrected (BCVA) distance visual acuity, corneal dioptric power in the flattest (K1) and steepest meridians (K2), mean corneal dioptric power (Km), asphericity (Q) and aberrometry (Coma) were recorded before (T1), 3-6 months (T2) and 6-9 months (T3) after ICRS implantation. The tunnels were created with manual technique and ICRS was implanted covering the coma axis. The inclusion criteria was a difference between the topographic flat axis and the coma axis superior to 30ᄎ. The surgical plan of ring implantation and the procedures were made by the same surgeon (AI).


Retrospective study involving 24 eyes of 22 patients [mean age 32.25ᄆ8.27; 64% female; 36% male]. The mean UDVA was 0.20ᄆ0.22 preoperatively and 0.40ᄆ0.29 and 0.48ᄆ0.21 postoperatively, T2 and T3 respectively (both p<0.05). The mean BCVA improved from 0.56ᄆ0.23 (T1) to 0.76ᄆ0.19 (T2; p <0.001) and 0.82ᄆ0.19 (T3; p<0.001). K1, K2 and Km showed a significant reduction of 1.74 diopters (D), 3.03D and 2.44D, respectively, (both p<0.05). The Q reduced after surgery from -0.62ᄆ0.22 (T1) to -0.29ᄆ0.28 and -0.27ᄆ0.23 (T2), (both p<0.001). The Coma showed an improvement from 2.69ᄆ1.08 to 1.75ᄆ1.05 in T2 (P<0.01), and to 1.82ᄆ0.90 in T3.


In eyes with paracentral KC with non-coincident topographic and coma axis, the ICRS implantation reduced topographic cylinder, the K1, K2, Q and coma in our study, with a significant improvement of visual outcomes.

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