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Intrastromal ring segment implantation in central keratoconus with regular astigmatism: the 'bow-tie' phenotype

Poster Details

First Author: L.Fernandez-Vega Cueto SPAIN

Co Author(s):    J. Alfonso   G. Ferrara   J. Merayo        

Abstract Details


To analyze the refractive and visual changes after the implant of Ferrara-type intraestromal ring segments (IRS) (AJL Ophthalmic, Spain) in central keratoconus with the 'bow-tie' fenotype.


Instituto Oftalmológico Fernández-Vega. Oviedo. Spain.


14 keratoconus with the 'bow-tie' fenotype that were implanted with IRS were analyzed. All the studied keratoconus meet the following inclusion criteria: Amsler-Krumeich stage I or II, anterior and posterior elevation map with the highest point at a distance ≤ 1.0 mm from the pupil center; thinnest pachymetry point at ≤ 1.0 mm from the pupil center; corneal thickness at the apex ≥ 400 µm and regular astigmatism ≥ 3.00D. The eyes with moderate astigmatism (3.00 to 5.00D) were implanted with 2 IRS of 120° of arc. The eyes with high astigmatism (≥ 5,00D) were implanted with 2 IRS of 90° of arc. The segments were always implanted at the 5mm optic zone. Snellen visual aquity without correction (UCVA) and with far correction (DCVA) as well as the refractive error were recorded and evaluated preoperatively and at six months post surgery.


Preoperative UCVA was 20/40 or worst in 12 eyes while, at six months, 11 eyes had an UCVA ≥ 20/40 or better. DCVA after surgery stayed at the same ppreop levels in 6 eyes and 8 eyes improved their DCVA. None of the eyes lost lines of DCVA. The safety and efficacy indexes were 0.79 and 1.21 respectively. Mean sphero-equivalent before surgery was -2.94 ± 1.63 D, and improved to 1.50 ± 1.41 D after surgery (P= 0.003). There was also an important reduction in the value of the blur vector which changed from 3.79 ± 1.44 D before surgery to 1.78 ± 1.43 D after the IRS implant (P=0.0002).


The implant nomogram of Ferrara-type IRS (AJL Ophthalmic) proposed in this study is safe and effective for the treatment of 'bow-tie' fenotype keratoconus. FINANCIAL INTEREST: NONE

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