Evaluation of 4 corneal astigmatic marking methods

PURPOSE: To compare 4 devices used to mark the cornea before astigmatism-reducing surgery. SETTING: Hanusch Krankenhaus, Vienna, Austria. DESIGN: Randomized examiner-masked clinical trial. METHODS: Patients were randomly allocated to 1 of 4 groups for preoperative corneal marking in the sitting position. The 4 methods used were marking at the slitlamp with an insulin needle, a pendular marker, a bubble marker, and a tonometer marker. The marks were then documented with a standardized photographic technique, and the rotational deviation and vertical misalignment were assessed. RESULTS: The study enrolled 60 patients. The pendular-marking device showed the least rotational deviation to the reference meridian (mean 1.8 degrees). There was no statistically significant difference between slitlamp marking and pendular marking (P = .05); however, there was a significant difference between the pendular marker and the bubble marker and between the pendular marker and the tonometer marker (P = .01 and P < .01, respectively). The least vertical misalignment was observed with the slitlamp-marking device (mean 0.28 mm). There was no statistically significant difference in vertical misalignment between the 4 groups. CONCLUSIONS: All marking devices showed a slight deviation to the horizontal reference meridian. Because small deviations of the meridian can result in a relevant reduction in the astigmatism-reducing effect with toric intraocular lenses, accurate marking of the cornea before surgery is critical due to the variable cyclotorsion caused by a change from the upright to the supine position.