Pupil decentration and iris tilting detected by Orbscan: Anatomic variations among healthy subjects and influence on outcomes of laser refractive surgeries

PURPOSE: To investigate the anatomic variations of entrance pupil decentration and tilting angle of the iris in healthy subjects and the influence of these factors on the outcome of laser in situ keratomileusis (LASIK). SETTING: Minamiaoyama Eye Clinic, Tokyo, Japan. METHODS: The degree of pupil decentration and tilting angle of the iris in 2280 eyes of 1144 myopic patients without abnormal findings by ophthalmologic examination were assessed using Orbscan. Of these, 901 eyes of 467 patients had LASIK. Multiple analysis of variance (ANOVA) was used to determine risk factors for reduction of postoperative best spectacle-corrected visual acuity (BSCVA) considering patient age, refractive power, tilting angle of the iris, pupil decentration, and corneal power. RESULTS: The mean pupil decentration in all eyes was 0.19 mm ± 0.11 (SD) (range 0 to 0.9 mm); tilting angle of the iris was 4.06 ± 1.41 degrees (range 0.19 to 12.69 degrees). By multiple ANOVA, refractive power, pupil decentration, and tilting angle of the iris were significant for the reduction of BSCVA. CONCLUSIONS: Some eyes with pupil decentration or tilting angle of the iris could not be detected under typical ophthalmologic examination but only with topographic examination. Attention should be paid to eyes with large pupil decentration and tilting angle of the iris because these may be risk factors for reduction of postoperative BSCVA during corneal refractive surgeries.