Intracorneal Ring Segments Exchange for Refractive Improvement in Keratoconus
Purpose
To present our surgical approach for intracorneal ring segments explantation and exchange for Ferrara® type segments in patients previously treated with unimproved visual acuity.
Methods
Retrospective study of patients thatwere submitted to exchange of corneal ring segments: Intaks SK® to Ferrara® rings. During preoperative and postoperative period data were analyzed regarding to best-corrected visual acuity (BCVA), spherical and cylindrical refractions, keratometry, vertical and horizontal coma and spherical aberration. All eyes were submitted to Ferrara® ring segment implantation 6,00 mm optical zone using the previous corneal tunnels. Curvature arc length was chosen based on new nomograms for keratoconus refractive surgery. Inclusion criteria include previous follow-up of 12 months or more after the first surgery, no gain of BCVA after the first surgery and no progression of the ectasia. Excluding criteria include patients with good refractive results with previous surgery and lack of follow-up. Ocular topography was performed using Oculus Pentacam (OCULUS , Wetzlar, Germany).
Results
We have included 8 eyes of 8 patients that were previously treated with Intacs SK® intracorneal rings. Three patients have duck-type keratoconus, two patients present with bow-type, two patients show snowman and one have croissant phenotype. Mean preoperative and postoperative BCVA was 0.32 and 0.63 on decimal scale. Preoperative and postoperative cylinder was 3.2D and 1.4D. Mean preoperative K1 was 46.1D, mean K2 of 51.2D with a maximum K of 54.7D. Mean postoperative K1 was 41.1D, mean K2 of 43.5D and a maximum K of 45D. Aberrometry parameters improved in all patients with a good stability during the follow-up period.
Conclusion
The new nomograms for intracorneal segments are based on subjective refraction, the axial curvature, the aberrometry (coma), corneal asphericity and the location of the thinnest point – it is the era of the ectasia phenotype classification and thus a new era of treatment, we can combine different arc lengths and thickness to provide the best approach depending on the ectasia phenotype. Refractive improvement and stability is observed in patients submitted to corneal ring segments exchange.