title: Arcuate relaxing incisions guided by corneal topography for postkeratoplasty astigmatism: vector and topographic analysis.
abstract: OBJECTIVE
  To determine if using corneal topography for planning arcuate relaxing incision placement for postkeratoplasty astigmatism improves clinical results.
  
  
  METHODS
  Twenty-six eyes with high levels (> 5 diopters [D]) of postkeratoplasty astigmatism were studied in a nonrandomized, retrospective, observational case series. Relaxing incisions were placed in the peripheral graft in each steep topographic hemimeridian. The following data were measured: keratometric, topographic, and refractive vector analysis; nonvector astigmatism reduction; surface regularity and asymmetry (surface regularity index and surface asymmetry index); topography patterns; surgical design; and visual acuity.
  
  
  RESULTS
  Topographic analysis changed some aspect of the surgery in 51/52 incisions with a 15.7 degrees mean change in incision location. The mean vector correction index (CI) was 0.89 to 0.92 for keratometric, topographic, and refractive indices. Sixty-five percent of eyes had surgically induced astigmatism (SIA) values within 2 D of the surgical goal. Eighty-one percent of eyes had at least a 50% reduction in net astigmatism and 85% had < or = 3-D residual refractive cylinder. The mean logMAR visual acuity increased 2 lines. The preoperative and postoperative spherical equivalent showed a high correlation (rho = 0.914, P = 0.000). The correlation between SIA and targeted induced astigmatism (TIA) was 0.56 (P = 0.003). There was a significant improvement in surface regularity index (P = 0.000) and surface asymmetry index (P = 0.05) values. No statistically significant correlations were found between total incision length and SIA or TIA, or between TIA and correction index. All patients had symmetric (58%) or asymmetric (42%) bowtie topographic patterns preoperatively with 35% achieving round/oval patterns postoperatively.
  
  
  CONCLUSIONS
  Topography-guided relaxing incision offers an easy method to plan surgery and has some limited advantages over conventional techniques.
authors.affiliation: Section of Ophthalmology, Virginia Mason Medical Center, Seattle, WA 98101, USA. ophhsg@vmmc.org
authors.forename: Harry S
authors.initials: HS
authors.lastname: Geggel
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001251:Astigmatism / Q000209:etiology / Q000601:surgery*; D003315:Cornea / Q000473:pathology / Q000601:surgery*; D019781:Corneal Topography / Q000379:methods*; D005260:Female; D006801:Humans; D015948:Keratoplasty, Penetrating; D007646:Keratotomy, Radial / Q000379:methods*; D008297:Male; D008875:Middle Aged; D011183:Postoperative Complications; D011379:Prognosis; D012189:Retrospective Studies; D014792:Visual Acuity