title: Astigmatism and biometric optic components of diode laser-treated threshold retinopathy of prematurity at 9 years of age.
abstract: OBJECTIVE
  To assess the prevalence of astigmatism and its relationship with biometric optic components in preterm school children with diode laser-treated threshold retinopathy of prematurity (ROP).
  
  
  METHODS
  A prospective, cross-sectional study in which cycloplegic keratometry, refraction, and ultrasound biometric measurement of optic components were performed on 24 consecutive preterm children with diode laser-treated threshold ROP at the age of 9 years. The study results were compared with data on 1021 age-matched full-term control children from a national survey.
  
  
  RESULTS
  The laser-treated eyes had a mean astigmatism of 3.47 D, with a mean spherical equivalent of -4.49 D. Of the 46 eyes studied, 98% of eyes showed astigmatism ≥0.5 D and 50% had high astigmatism (>3.0 D). Most astigmatic eyes (97.7%) showed with-the-rule astigmatism, with the mean plus cylinder axis at 89.30(o). Further correlation analysis showed the astigmatism in refraction was highly correlated with the corneal astigmatism (r=0.921, P<0.001) and the vertical corneal curvature (r=0.405, P=0.005). There was significantly steeper vertical corneal curvature (P=0.003) and flatter horizontal corneal curvature (P=0.031) in eyes with laser-treated ROP when compared with age-matched full-term controls. The eyes with laser-treated ROP also show significantly thicker lens (3.93 mm) and shallower anterior chamber depth (ACD; 2.92 mm) than full-term controls (P<0.001).
  
  
  CONCLUSIONS
  There is significantly higher prevalence and greater magnitude of astigmatism in eyes with laser-treated threshold ROP compared with full-term controls. The steeper vertical corneal curvature component contributes to the increased astigmatism in eyes with laser-treated ROP.
authors.affiliation: Department of Ophthalmology, Taipei Veterans General Hospital, Taipei, Taiwan, Republic of China. csyang@vghtpe.gov.tw
authors.forename: C-S
authors.initials: CS
authors.lastname: Yang
authors.forename: A-G
authors.initials: AG
authors.lastname: Wang
authors.forename: Y-F
authors.initials: YF
authors.lastname: Shih
authors.forename: W-M
authors.initials: WM
authors.lastname: Hsu
mesh_terms: D001251:Astigmatism / Q000453:epidemiology / Q000503:physiopathology*; D001699:Biometry; D002648:Child; D003315:Cornea / Q000473:pathology*; D003430:Cross-Sectional Studies; D005260:Female; D005865:Gestational Age; D006801:Humans; D007231:Infant, Newborn; D017075:Laser Coagulation; D054023:Lasers, Semiconductor / Q000627:therapeutic use*; D008297:Male; D033401:Microscopy, Acoustic; D009216:Myopia / Q000453:epidemiology / Q000503:physiopathology; D047928:Premature Birth; D015995:Prevalence; D011446:Prospective Studies; D012029:Refraction, Ocular / Q000502:physiology; D012178:Retinopathy of Prematurity / Q000601:surgery*; D013624:Taiwan / Q000453:epidemiology; D014792:Visual Acuity / Q000502:physiology