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Steven A Greenstein, Peter S Hersh; Symmetric vs. Asymmetric Intracorneal Ring Segment placement with Adjunctive Corneal Collagen Crosslinking for Keratoconus and Corneal Ectasia. Invest. Ophthalmol. Vis. Sci. 2014;55(13):4227.
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© ARVO (1962-2015); The Authors (2016-present)
To determine the effect of symmetric vs asymmetric intracorneal ring segment (Intacs®) placement, with corneal collagen crosslinking (CXL), on visual and topographic outcomes in patients with keratoconus (kc) and corneal ectasia (ec).
61 eyes (46 KC and 15EC) were analyzed in a prospective randomized control clinical trial. Eyes were divided into three groups: those with symmetric Intacs® placed (either two 450µm or two 350µm segments), those with asymmetric Intacs® placed (450µm/210µm segments), and those with a single Intacs® placed (450 µm or 400 µm segments). Statistical analysis was performed on those eyes with two symmetric or asymmetric Intacs placed. The six month outcomes analyzed included uncorrected (UCVA) and best corrected (BCVA) visual acuity, maximum (Kmax), flat (Kf), steep (Ks), and average (Kavg) keratometry, and the point of maximum flattening (Pmax) as measured by the Pentacam.
Overall (n=61), at 6 months, UCVA significantly improved from logMAR 0.94 ± 0.32 to 0.77 ± 0.30 (p<0.01), and BCVA changed from 0.39 ± 0.26 to 0.26 ± 0.17 (P<0.01). Topographically, Kmax, Kavg,, Kf, Ks, changed from 59.8 ± 7.7D to 59.3 ± 8.5D (p=0.2), 49.8 ± 5.6D to 48.2 ± 5.7D (p<0.01), 47.8 ±5.3D to 46.6 ± 5.5D (p<0.01), 52.9 ± 6.2D to 49.9 ± 6.1D (p<0.01), respectively. On average Pmax flattened by 6.5 ± 2.0D, 6 months after Intacs®/CXL . When the symmetric (n=33) vs asymmetric (n=22) groups were compared, there was no statistical difference between the visual or topographic outcomes, 6 months after Intacs®/CXL. Additionally, similar visual and topographic improvement was seen in a limited number of single Intacs® eyes (n=6).
Overall, eyes treated with symmetric or asymmetric Intacs®, and adjunctive CXL therapy experienced an improvement in corneal topography, UCVA, and BCVA, 6 months after therapy. There was no difference between symmetric vs asymmetric Intacs® treatment 6 months after therapy. Future studies will be preformed to analyze the placement of a single Intacs with adjunctive CXL therapy.
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