Refractive and Visual Outcomes After Intacs vs Ferrara Intrastromal Corneal Ring Segment Implantation for Keratoconus: A Comparative Study

PURPOSE: To evaluate the refractive, topographic, optical, visual acuity, and quality outcomes of two types of intrastromal corneal ring segments (ICRS) in the treatment of keratoconus. METHODS: In this retrospective study, 16 eyes that had been implanted with Intacs ICRS (Addition Technology Inc) (Intacs group) and 17 eyes implanted with Ferrara ICRS (Ferrara Ophthalmics Ltda) (Ferrara group) were evaluated. Pre- and postoperative examinations included uncorrected and corrected distance visual acuities (UDVA and CDVA, respectively), manifest refraction, slit-lamp examination, topography, and ocular wavefront analysis. Contrast sensitivity measurements under photopic, scotopic, and scotopic with glare conditions were performed 1 year postoperatively. RESULTS: One year postoperatively, a significant decrease was noted in spherical equivalent refractive error of 3.76 +/- 0.39 diopters (D) and 3.42 +/- 0.88 D and keratometry of 3.43 +/- 0.24 D and 3.28 +/- 0.78 D in the Intacs and Ferrara groups, respectively; and increase in mean UDVA and CDVA in Snellen lines of 0.18 +/- 0.04 and 0.21 +/- 0.05, respectively, in the Intacs group and 0.21 +/- 0.09 and 0.26 +/- 0.08, respectively, in the Ferrara group (P<.01 for all). The postoperative increase in UDVA and CDVA and decrease in keratometry readings were not significantly different between groups (P>.05 for all). Mean higher order aberrations decreased in the Intacs group and increased in the Ferrara group (P>.05 for both). Postoperatively, a signifi cant decrease was noted in scotopic contrast sensitivity when glare was introduced in the Ferrara group, which was positively correlated with pupil diameter (r(15)= 0.50, P=.04). CONCLUSIONS: Both ICRS types provided comparable refractive, topographic, and optical quality outcomes. Eyes with Ferrara ICRS experienced greater decrease in scotopic contrast sensitivity under glare, which was significantly correlated with pupil diameter. [J Refract Surg. 2011; 27(12): 907-912.] doi:10.3928/1081597X-20110906-03