title: Effect of Paired Opposite Clear Corneal Incisions on With-the-Rule Versus Against-the-Rule Astigmatism.
abstract: OBJECTIVE
  To determine the refractive effects of paired opposite clear corneal incisions (OCCIs) on with-the-rule (WTR) and against-the-rule (ATR) astigmatism at 1 and 6 months postoperatively.
  
  
  METHODS
  This is a retrospective cohort study. Consecutive eyes from different patients who had OCCIs for keratometric astigmatism of 1.5 to 2.5 diopters (D) were included. They were divided into group A with the steepest meridian at 90 ± 20 and groups B and group C with the steepest meridian at 180 ± 20 degrees. The keratome width used for groups A and B was 3.2 mm and for group C was 3.5 mm. Keratometry by partial coherence interferometry, manifest refraction, and visual acuities were measured at 1 and 6 months postoperatively.
  
  
  RESULTS
  Twenty-eight eyes were included in each group. The median of surgically induced astigmatism (SIA) magnitude at 1 month postoperatively for groups A, B, and C were 1.7, 1.1, and 1.7 D, respectively (P < 0.001). A post hoc test showed that SIAs of groups A and C were significantly greater than that of group B. Six months postoperatively, the medians were 1.6, 0.8, and 1.5 D (P < 0.001). The change was significantly different from 1 month for groups B and C (P = 0.001 and P = 0.006, respectively). The median uncorrected distant visual acuity was better for groups A and C compared with group B at 1 month (P = 0.016).
  
  
  CONCLUSIONS
  A paired OCCI has a significantly greater refractive effect on WTR than ATR astigmatism correction. The SIA for ATR astigmatism reduces significantly more than for WTR astigmatism correction at 6 months.
authors.affiliation: *Eye Care Centre, Leighton Hospital, Cheshire, United Kingdom; and †Department of Eye, Leicester Royal Infirmary, Leicestershire, United Kingdom.
authors.forename: Patrick J
authors.initials: PJ
authors.lastname: Chiam
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001251:Astigmatism / Q000503:physiopathology*; D001699:Biometry; D003315:Cornea / Q000503:physiopathology / Q000601:surgery*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D019654:Lens Implantation, Intraocular; D008297:Male; D008875:Middle Aged; D018918:Phacoemulsification / Q000379:methods*; D012029:Refraction, Ocular / Q000502:physiology; D012189:Retrospective Studies; D014792:Visual Acuity / Q000502:physiology