title: Assessment of refractive astigmatism and simulated therapeutic refractive surgery strategies in coma-like-aberrations-dominant corneal optics.
abstract: BACKGROUND
  The aim of the study is to raise the awareness of the influence of coma-like higher-order aberrations (HOAs) on power and orientation of refractive astigmatism (RA) and to explore how to account for that influence in the planning of topography-guided refractive surgery in eyes with coma-like-aberrations-dominant corneal optics.
  
  
  METHODS
  Eleven eyes with coma-like-aberrations-dominant corneal optics and with low lenticular astigmatism (LA) were selected for astigmatism analysis and for treatment simulations with topography-guided custom ablation. Vector analysis was used to evaluate the contribution of coma-like corneal HOAs to RA. Two different strategies were used for simulated treatments aiming to regularize irregular corneal optics: With both strategies correction of anterior corneal surface irregularities (corneal HOAs) were intended. Correction of total corneal astigmatism (TCA) and RA was intended as well with strategies 1 and 2, respectively.
  
  
  RESULTS
  Axis of discrepant astigmatism (RA minus TCA minus LA) correlated strongly with axis of coma. Vertical coma influenced RA by canceling the effect of the with-the-rule astigmatism and increasing the effect of the against-the-rule astigmatism. After simulated correction of anterior corneal HOAs along with TCA and RA (strategies 1 and 2), only a small amount of anterior corneal astigmatism (ACA) and no TCA remained after strategy 1, while considerable amount of ACA and TCA remained after strategy 2.
  
  
  CONCLUSIONS
  Coma-like corneal aberrations seem to contribute a considerable astigmatic component to RA in eyes with coma-like-aberrations dominant corneal optics. If topography-guided ablation is programmed to correct the corneal HOAs and RA, the astigmatic component caused by the coma-like corneal HOAs will be treated twice and will result in induced astigmatism. Disregarding RA and treating TCA along with the corneal HOAs is recommended instead.
authors.affiliation: SynsLaser Kirurgi AS, Tromsø, Troms Norway ; School of Ophthalmology and Optometry, Wenzhou Medical University, Wenzhou, China.
authors.forename: Wen
authors.initials: W
authors.lastname: Zhou
authors.affiliation: SynsLaser Kirurgi AS, Tromsø, Troms Norway ; Eye Department, University Hospital North Norway, Tromsø, Norway.
authors.forename: Aleksandar
authors.initials: A
authors.lastname: Stojanovic
authors.affiliation: Department of Ophthalmology, Vestre Viken Hospital Trust, Drammen, Norway ; Department of Medical Biochemistry, Oslo University Hospital, Oslo, Norway ; Department of Oral Biology, Faculty of Dentistry, University of Oslo, Oslo, Norway.
authors.forename: Tor Paaske
authors.initials: TP
authors.lastname: Utheim
keywords: Coma; Corneal irregular astigmatism; Higher-order-aberrations; Topography-guided ablation