Choosing the location of corneal incision based on preexisting astigmatism in phacoemulsification

PURPOSE: To investigate the best location of clear, cornea incision in phacoemulsification, depending on preexisting corneal astigmatism. DESIGN: Randomized clinical trial and noncomparative interventional case series. METHODS: A total of 574 patients in five stages were assigned to the following incisions: superior or temporal (n = 89), superior (n = 141), superior or superior plus relaxing (n = 102), nasal or temporal (n = 156), and incisions based on applying conclusions of preceding and current studies (n = 86). Visual acuity, refraction, biomicroscopy, keratometry, and videokeratography (Fourier analysis) were performed before and after phacoemulsification and intraocular lens implantation (3.5 mm incision). MAIN OUTCOME MEASURES: Corneal refractive and surface regularity index change between preoperative and 6-month postoperative examination. Visual acuity at 6 months. RESULTS: In patients without corneal astigmatism, corneal changes induced were greater in superior than temporal incision. After a superior incision (preoperative steep axis at 90 degrees), a shift of the axis 90 degrees away was less likely with at least 1.5 diopters of astigmatism. A perpendicular relaxing limbal incision decreased corneal changes. Nasal incision induced greater corneal change than temporal incision (preoperative steep axis at 180 degrees). A shift of this axis 90 degrees away was more likely with astigmatism < 0.75 diopters in temporal incision and < 1.25 diopters in nasal incision. CONCLUSIONS: Superior incision is recommended with at least 1.5 diopters of astigmatism and steep axis at 90 degrees. Temporal incision is recommended with astigmatism < 1.5 diopters and steep axis at 90 degrees, negligible astigmatism, or astigmatism < 0.75 diopters and steep axis at 180 degrees. Nasal incision is recommended with at least 0.75 diopters of astigmatism and steep axis at 180 degrees. (c) 2005 by Elsevier Inc. All rights reserved.