title: Accuracy of a new photo-refractometer in young and adult patients.
abstract: BACKGROUND
  Photorefraction can be carried out in both eyes simultaneously from a distance and is therefore suitable for examination of children. This study evaluated the accuracy of a commercially available photo-refractometer (Power Refractor, Plusoptix, Erlangen, Germany) and investigated whether the working distance relaxes the accommodation sufficiently without cycloplegia.
  
  
  METHODS
  Photo-refractometer readings were compared to cycloplegic retinoscopy. Because of the limited working range the group of patients consisted of low and moderate ametropic eyes within a spherical power of -7.0 to +5.0 D. One hundred and ninety-two eyes from 104 patients (2-81 years) were photo-refracted under cycloplegia. A subgroup of 83 eyes from 46 patients was additionally refracted without cycloplegia.
  
  
  RESULTS
  Under cycloplegia, the Power Refractor measured the spherical equivalent slightly below that of cycloplegic retinoscopy (too much minus). The mean difference in spherical equivalent was -0.12+/-0.91 D (SD). The mean difference of cylindrical power was -0.17+/-0.73 D. The mean weighted axis difference was 0.61+/-0.71 D which is comparable to an axis deviation of 18 degrees at a cylinder power of 1.00 D. Without cycloplegia, the mean difference of the spherical equivalent was -0.73+/-1.25 D. The mean difference of cylindrical power was -0.20+/-0.65 D. The mean weighted axis difference was 0.44+/-0.58 D which is comparable to an axis deviation of 13 degrees at a cylinder power of 1.00 D.
  
  
  CONCLUSIONS
  Without cycloplegia, the spherical equivalent of the Power Refractor tends to be underestimated due to uncontrolled accommodation, especially in children. Cycloplegia improves the accuracy in evaluating the spherical equivalent, but decreases the accuracy of cylinder power and axis.
authors.affiliation: Sektion Neuroophthalmologie, Kinderophthalmologie, Schielbehandlung Universitäts-Augenklinik, Killianstr. 5, 79106 Freiburg, Germany. Schimi@aug.ukl.uni-freiburg.de
authors.forename: Thilo
authors.initials: T
authors.lastname: Schimitzek
authors.forename: Wolf A
authors.initials: WA
authors.lastname: Lagrèze
mesh_terms: D000065:Accommodation, Ocular / Q000502:physiology; D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002648:Child; D002675:Child, Preschool; D003519:Cyclopentolate / Q000008:administration & dosage; D003941:Diagnostic Techniques, Ophthalmological / Q000295:instrumentation*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009184:Mydriatics / Q000008:administration & dosage; D011680:Pupil / Q000187:drug effects; D012029:Refraction, Ocular / Q000502:physiology*; D012030:Refractive Errors / Q000175:diagnosis; D015203:Reproducibility of Results; D042262:Retinoscopy / Q000592:standards
chemical_list: D009184:Mydriatics; D003519:Cyclopentolate