Analysis of centration of Intacs segments implanted with a femtosecond laser

PURPOSE: To analyze the centration of intrastromal ring segments (Intacs, Addition Technology, Inc.) implanted using a femtosecond laser in eyes with keratoconus. SETTING: Kudret Eye Hospital, Ankara, Turkey. METHODS: In a retrospective noncomparative case series, the distance of deviation of the intrastromal ring segment from the pupillary center was evaluated in 59 eyes of 39 keratoconic patients after tunnel creation with a femtosecond laser. The distance of deviation of segments from the pupillary edge and direction of decentration were analyzed using the anterior segment analyzer of the Pentacam Scheimpflug photographic camera (Oculus Opticgerate GmbH). RESULTS: Intacs were successfully implanted in all eyes. The mean horizontal deviation was 788.33 microm +/- 500.34 (SD) (range 30 to 2450 microm), and there was a temporal displacement in all eyes. The mean vertical deviation was 370.83 +/- 343.17 microm (range 0 to 1690 microm), and there was an inferior displacement in 28.81% of eyes and superior displacement in 66.10% of eyes. There was no vertical displacement in 3 eyes (5.08%). CONCLUSION: During applanation for Intacs correction by a femtosecond laser, the cornea and pupil are not in their natural position, which leads to decentration and misalignment of the segments.