title: Clinical importance of accurate refractor vertex distance measurements prior to refractive surgery.
abstract: OBJECTIVE
  To determine directly measured vertex distances in a consecutive series of patients refracted at a refractor and to examine the clinical importance of such a measurements for improving refractive surgical results.
  
  
  METHODS
  Vertex distance measurements were obtained in 189 consecutive patients by using a new device capable of taking direct and accurate measurements behind a refractor. Eyelid thickness was measured with an industrial caliper in five patients.
  
  
  RESULTS
  The average true vertex distance was 20.4 mm with a range of 10 to 34 mm. Eyelid thickness was 3 mm in all five patients.
  
  
  CONCLUSIONS
  Precise measurement of true refractor vertex distance is important for accuracy of refractive surgical procedures. The practice of assuming an average vertex distance of 12 to 14 mm for all refractive patients underestimates the vertex distance in many patients refracted at the refractor, resulting in overcorrecting minus and undercorrecting plus refractions.
authors.affiliation: Department of Ophthalmology, University of California, Irvine, USA. drweiss@drweiss.com
authors.forename: Richard A
authors.initials: RA
authors.lastname: Weiss
authors.forename: William
authors.initials: W
authors.lastname: Berke
authors.forename: Larry
authors.initials: L
authors.lastname: Gottlieb
authors.forename: Peter
authors.initials: P
authors.lastname: Horvath
mesh_terms: D005139:Eyeglasses; D005143:Eyelids / Q000033:anatomy & histology*; D006801:Humans; D054140:Refractive Surgical Procedures; D014787:Vision Tests / Q000295:instrumentation / Q000379:methods*