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Changes in total corneal and refractive astigmatism using intracorneal ring segments of 90 degrees in keratoconus

Poster Details

First Author: M.Nuñez COLOMBIA

Co Author(s):    C. Blanco              

Abstract Details


To evaluate the effectiveness of the intracorneal ring segments, INTACS, of 90 degrees in patients diagnosed with centered keratoconus with astigmatism plus hyperopia through changes in topographical and refractive astigmatism


Clinica de Oftalmologia de Cali, Pontificia Universidad Javeriana-Cali, Cali,Colombia


A non-randomized experimental prospective controlled study with a non-probabilistic sample, including 20 patients with a diagnosis of centered keratoconus grade I, II and III according to the Amsler-Krumeich criteria and astigmatism greater than the spherical defect. Two intracorneal rings were implanted according to Intacs nomogram version 3.1 in 7 mm tunnel. Magnitude and axis of topographical (total corneal power) and refractive astigmatism was obtaining pre- operative and 3 months post-operative. We measured the surgical induced astigmatism (SIA) in minus cylinder form in a way to determine if there were over or under corrections regarding the target- induced astigmatism (TIA).


In the preoperative, the uncorrected distance visual acuity (UCVA) was of 1,0 (LogMar) and the best spectacle corrected visual acuity (BSCVA) of 0,25. The total corneal astigmatism values were 4,60 D @ 89° and 2,10 D @92° in the refractive plane. At 3 months post-operative, the UCVA and BSCVA were 0,52 and 0,22 respectively , the total corneal astigmatism was 2,60 @ 88 ° and the refractive astigmatism was 0,50 D @ 100°. The total corneal SIA was 1,97D @ 159° and the refractive SIA was 1,62 @ 180°, both in plus-cylinder form.


The good result of refractive SIA showed correlation with the improvement in the visual acuity of the patients. We found a total corneal SIA under-correction in keratoconus treatment with rings of 90°, which clinically is required to avoid an overcorrection of coupling effect in the flat meridian and then to avoid hyperopic shift post operative. Finally this is important to improve the visual rehabilitation of the patient. FINANCIAL INTEREST: One of more of the authors... travel has been funded, fully or partially, by a competing company

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