title: Evaluating the effect of splitting cylindrical power on improving patient tolerance to toric lens misalignment.
abstract: OBJECTIVE
  Evaluating the impact of splitting toric power on patient tolerance to misorientation such as with intraocular lens rotation.
  
  
  METHODS
  University vision clinic.
  
  
  METHODS
  Healthy, non astigmats had +1.50D astigmatism induced with spectacle lenses at 90°, 135°, 180° and +3.00D at 90°. Two correcting cylindrical lenses of the opposite sign and half the power each were subsequently added to the trial frame misaligned by 0°, 5° or 10° in a random order and misorientated from the initial axis in a clockwise direction by up to 15° in 5° steps. A second group of adapted astigmats with between 1.00 and 3.00DC had their astigmatism corrected with two toric spectacle lenses of half the power separated by 0°, 5° or 10° and misorientated from the initial axis in both directions by up to 15° in 5° steps. Distance, high contrast visual acuity was measured using a computerised test chart at each lens misalignment and misorientation.
  
  
  RESULTS
  Misorientation of the split toric lenses caused a statistically significant drop in visual acuity (F=70.341; p<0.001). Comparatively better acuities were observed around 180°, as anticipated (F=3.775; p=0.035). Misaligning the split toric power produced no benefit in visual acuity retention with axis misorientation when subjects had astigmatism induced with a low (F=2.190, p=0.129) or high cylinder (F=0.491, p=0.617) or in the adapted astigmats (F=0.120, p=0.887).
  
  
  CONCLUSIONS
  Misalignment of toric lens power split across the front and back lens surfaces had no beneficial effect on distance visual acuity, but also no negative effect.
authors.affiliation: Aston University, School of Life and Health Sciences, Ophthalmic Research Group, Birmingham B4 7ET, UK.
authors.forename: Sandeep K
authors.initials: SK
authors.lastname: Dhallu
authors.affiliation: Aston University, School of Life and Health Sciences, Ophthalmic Research Group, Birmingham B4 7ET, UK.
authors.forename: Amy L
authors.initials: AL
authors.lastname: Sheppard
authors.affiliation: Aston University, School of Life and Health Sciences, Ophthalmic Research Group, Birmingham B4 7ET, UK. Electronic address: j.s.w.wolffsohn@aston.ac.uk.
authors.forename: James S
authors.initials: JS
authors.lastname: Wolffsohn
mesh_terms: D000328:Adult; D001251:Astigmatism / Q000175:diagnosis* / Q000209:etiology* / Q000517:prevention & control; D005260:Female; D006801:Humans; D019654:Lens Implantation, Intraocular / Q000009:adverse effects*; D007910:Lenses, Intraocular / Q000009:adverse effects*; D008297:Male; D017060:Patient Satisfaction; D017755:Prosthesis Fitting / Q000009:adverse effects*; D016896:Treatment Outcome
keywords: Astigmatism; Intraocular lenses; Misalignment; Misorientation; Toric