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Themistoklis Tsintarakis, Timo Eppig, Achim Langenbucher, Berthold Seitz, Moatasem El-Husseiny; Effect of geometrical parameters on the change of corneal functionality with femtosecond laser-assisted INTACS-SK implantation in patients with corneal ectasias. Invest. Ophthalmol. Vis. Sci. 2016;57(12):4868.
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© ARVO (1962-2015); The Authors (2016-present)
To evaluate the effect of geometry of corneal ring implants (INTACS SK) and their intrastromal position on the change of functional outcome with treatment of keratoconus, pellucid marginal degeneration and post-LASIK keratectasia.
The CASIA SS-1000 swept-source OCT was used to image the implanted INTACS SK of size 210, 300, 350, 400, 450 and 500 µm 3 months postoperatively in 60 eyes of 51 patients (mean age 35.8 ± 10.6 years) who underwent femtosecond laser-assisted corneal ring segment implantation between August 2011 and June 2015. Mean and maximum corneal power (Kmean and Kmax) derived from Pentacam HR, spherical equivalent and refractive cylinder from subjective refraction as well as spectacle-corrected visual acuity were assessed preoperatively as well as 3 months postoperatively and the change from pre- to postoperative follow-up was derived. From HighRes cornea mode OCT measurements we extracted geometric parameters on meridional sections perpendicular to the implantation axis as follows: thickness and width of the corneal ring implants, the distance of the ring to the anterior and posterior corneal surface, the thickness of the surrounding cornea 350 µm central and peripheral to the implanted ring segment. Moreover the lateral positioning of the ring implants relative to the pupil centre was assessed.
Spherical equivalent / refractive cylinder from subjective refraction changed from -9.95±5.99 dpt / -6.25±2.04 dpt preoperatively to -2.88±3.14 / -2.52±1.74 dpt 3 months after surgery (p<0.001 both). Kmean / Kmax from Pentacam decreased from 48.89±4.45 / 57.51±6.12 dpt preoperatively to 45.99±3.94 / 55.44±6.02 dpt 3 months postoperatively (p<0.001 / p=0.017). Spectacle corrected VA increased from 0.41±0.10 preoperatively to 0.69±0.20 3 months postoperatively (p<0.001).In a generalized linear model (GLM) the change in spherical equivalent and in Kmean (dependent variables), described with the effect sizes of measured geometric parameters (covariates), was significantly affected only by the thickness of the ring segment (R=26.393, p=0.006 / R=-10.33, p=0.022).
Our results imply that mostly the thickness of the ring segments shows an effect on the reduction of maximum corneal power and increase of spherical equivalent of subjective refraction after INTACS-SK implantation.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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