Corneal descriptive indices in the fellow eye of unilateral keratoconus.

OBJECTIVES: To determine whether indices derived from corneal topography could be used to differentiate between three populations at varying degrees of risk for presenting keratoconus, but otherwise unremarkable clinical appearance. METHODS: Eighty subjects lacking clinical signs of keratoconus were divided into three groups according to their background. Fifty refractive surgery candidates were used as controls, to be compared with 15 clinically normal fellow eyes of subjects with unilateral keratoconus, and 15 eyes from first and second degree relatives of the former keratoconic patients. Corneal topography indices (curvature, wavefront, and thickness) were obtained from Placido disc (Keratron) and scanning-slit (Orbscan) devices. Receiver operator characteristic curve analysis (sensitivity, specificity, and area under the curve) was performed to highlight the ability of any single index to discriminate between groups, and cutoff values for a fixed 0.80 specificity were determined. RESULTS: Corneal wavefront indices (root mean square and vertical coma) exhibited the best performance for discriminating between controls and the fellow eye of unilateral keratoconus patients. Corneal curvature and thickness indices showed poor capability to differentiate between the groups. Relatives and controls were distinguishable by a single thickness parameter. CONCLUSIONS: The proposed cutoff values between controls and patients at risk for keratoconus may prove useful for screening purposes.

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 Oftalmológico 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< or =.0001). In Group B, the preoperative mean BSCVA was 0.36 (20/63) and the postoperative mean BSCVA, 0.24 (20/80) (P< or =.02). The preoperative mean sphere power was 3.90 diopters (D) greater in Group B than in Group A (P< or =.007); the mean spherical equivalent was 4.36 D greater (P< or =.007), and the mean K-reading was 6.91 D greater (P< or =.001). The postoperative reduction in spherical dioptric power was 2.11 D (P< or =.027) and the mean spherical equivalent, 2.81 D (P< or =.003), significant only in Group A. The reduction in mean central K-readings was 4.30 D (P< or =.0001) in Group A and 6.19 D (P< or =.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 < or =53 D. In Group B, 4 eyes (80%) had a mean K-reading > or =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 (< or =53 D) and a relatively low spherical equivalent. In advanced keratoconus (mean K-reading > or =55 D), poor results can be anticipated.