Comparison of single-segment and double-segment intacs for keratoconus and post-LASIK ectasia

PURPOSE: To evaluate the efficacy of single-segment Intacs and compare with double-segment Intacs in subjects with post,LASIK ectasia and keratoconus. DESIGN: Retrospective comparative analysis. METHODS: SETTING: Boxer Wachler Vision Institute, Beverly Hills, California, USA. STUDY POPULATION: Thirty,seven eyes of 28 patients with keratoconus and post-LASIK ectasia classified into two groups: single-segment group ( 17 eyes, 11 patients) and double-segment group (20 eyes, 17 patients). Both groups were matched for age, visual acuity (uncorrected, UCVA; best spectacle-corrected, BSCVA), refractive error (sphere, cylinder, spherical equivalent), and keratometry (K) value (flat, steep, average) by t test for equality of means. INTERVENTION: Single- or double,segment Intacs procedure with axis of incision for insertion in the steep axis of manifest refraction. MAIN OUTCOME MEASURE. Improvement of acuity, refractive error, K values, and inferior-superior (I-S) ratio. RESULTS: There was more improvement in UCVA in the single segment group (nine lines) than the double-segment group (2.5 lines), P < .01; in BSCVA in the single,segment group (2.5 lines) than the double,segment group (< 1 line), P < .01; in steep K values in the single,segment group (2.76 diopters +/- 2.68) than the double-segment group (0.93 diopters +/- 2.01), P = .02; and in I,S ratio in the single,segment group (9.51 +/- 7.49) than the double-segment group (4.22 +/- 4.82), P = .01; and greater cylinder decrease after Holladay vector analysis in the single,segment group (5.69 diopters +/- 3.10) than the double-segment group (1.58 diopters +/- 3.09), P < .01. CONCLUSIONS: Single,segment Intacs improved both UCVA and BSCVA by differential flattening of inferior meridian and steepening of superior meridian as reflected by change in I-S ratio.