Analysis of results related to good and bad outcomes of Intacs implantation for keratoconus correction

PURPOSE: To evaluate factors influencing good and poor outcomes after intracorneal ring segment implantation to correct keratoconus. SETTING: Instituto Oftalmologico de Alicante (Vissum Corporation), University of Miguel Hernandez, Alicante, Spain. METHODS: A retrospective comparative study of the visual outcome, 25 eyes of 21 patients were implanted after intracorneal ring segments (Intacs, Addition Technology) as a method to correct keratoconus. Outcomes were evaluated 6 months after implantation based on the visual results. Group A comprised 20 eyes that gained 3 lines or more of best spectacle-corrected visual acuity (BSCVA) to correct keratoconus, and Group B comprised 5 eyes that lost 1 line of BSCVA. RESULTS: In Group A, the preoperative mean BSCVA was 0.43 (20/50) and the postoperative mean BSCVA, 0.82 (20/20) (P <=.0001). In Group B, the preoperative mean BSCVA was 0.36 (20/63) and the postoperative mean BSCVA, 0.24 (20/80) (P <=.02). The preoperative mean sphere power was 3.90 diopters (D) greater in Group B than in Group A (P <=.007); the mean spherical equivalent was 4.36 D greater (P <=.007), and the mean K-reading was 6.91 D greater (P <=.001). The postoperative reduction in spherical dioptric power was 2.11 D (P <=.027) and the mean spherical equivalent, 2.81 D (P <=.003), significant only in Group A. The reduction in mean central K-readings was 4.30 D (P <=.0001) in Group A and 6.19 D (P <=.014) in Group B. The correlation of the preoperative mean K value to the postoperative BSCVA was significant at the .01 level by the Pearson test (-0.67). In Group A, all eyes (100%) had a mean K-reading <= 53 D. In Group B, 4 eyes (80%) had a mean K-reading >= 55 D. CONCLUSION: Intacs provided better results in visual acuity and corneal topography quality and significantly reduced the spherical equivalent in eyes with keratoconus with relatively low mean K values (<= 53 D) and a relatively low spherical equivalent. In advanced keratoconus (mean K-reading >= 55 D), poor results can be anticipated.