title: Axis difference between corneal and internal astigmatism to consider for toric intraocular lenses.
abstract: OBJECTIVE
  To evaluate the axis difference between corneal and internal astigmatism in patients with cataract, because if the axis of corneal astigmatism is opposite to the axis of internal astigmatism, the amount of refractive astigmatism will increase after cataract surgery owing to disappearance of the neutralizing effect of the crystalline lens on corneal astigmatism.
  
  
  METHODS
  Retrospective cross-sectional study.
  
  
  METHODS
  One hundred eighty patients (180 eyes) who underwent cataract surgery were enrolled. Preoperative refractive, corneal, and internal astigmatism were measured using a wavefront analyzer and retrospectively analyzed. On-axis was defined as an axis difference between corneal and internal astigmatism of 180 ± 10 degrees. Opposite-axis was defined as an axis difference between corneal and internal astigmatism of 90 ± 10 degrees. The remaining cases were defined as oblique-axis.
  
  
  RESULTS
  Corneal and internal astigmatic vectors showed a tendency to have the opposite direction. An on-axis difference was seen in 10.0% of patients (18 eyes), oblique-axis in 69.4% of patients (125 eyes), and opposite-axis in 20.6% of patients (37 eyes). Of all eyes, 10.0% had an opposite-axis difference with more than 1.00 diopter (D) of both corneal and internal astigmatism. The percentage of eyes with an opposite-axis difference between corneal and internal astigmatism had a tendency to increase as corneal and internal astigmatism increased (P = .030 and P = .003, respectively).
  
  
  CONCLUSIONS
  A total of 10.0% of all eyes with cataract had an opposite-axis difference with more than 1.00 D of both corneal and internal astigmatism. In these cases, surgical techniques to reduce corneal astigmatism, such as a toric intraocular lens, should be recommended to increase patient satisfaction.
authors: Department of Ophthalmology, Korea University College of Medicine, Seoul, South Korea.
authors: Youngsub
authors: Y
authors: Eom
authors: Ki Tae
authors: KT
authors: Nam
authors: Su Yeon
authors: SY
authors: Kang
authors: Hyo Myung
authors: HM
authors: Kim
authors: Jong Suk
authors: JS
authors: Song
mesh_terms: D057128:Aberrometry; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000867:Anterior Chamber / Q000473:pathology; D001251:Astigmatism / Q000175:diagnosis* / Q000628:therapy; D058452:Axial Length, Eye / Q000473:pathology*; D002387:Cataract Extraction; D003315:Cornea / Q000473:pathology*; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D019654:Lens Implantation, Intraocular; D007910:Lenses, Intraocular; D008297:Male; D008875:Middle Aged; D015995:Prevalence; D012029:Refraction, Ocular / Q000502:physiology; D012189:Retrospective Studies; D014792:Visual Acuity / Q000502:physiology