title: The gradient filter test to assess amblyopia.
abstract: A new technique, the gradient filter test, was developed for evaluating changes in the visual acuity of preverbal children undergoing treatment for amblyopia. The gradient filter test consists of a series of calibrated photographic fog filter and prism lenses. The combined prism-filter lenses are placed in front of the normal fixing eye. The greatest density (fogging value) filter that causes a switch in fixation from the amblyopic to the normal eye is noted. In both normal eyes of 20 nonamblyopic patients and the fellow (non-amblyopic) eyes of 20 amblyopic patients, visual acuity decreased as the density of the prism-filter lens increased. The gradient filter test accurately detected an improvement in visual acuity when compared with optotype measurements in eight patients undergoing occlusion therapy. The gradient filter test is a useful clinical tool that can assess changes in visual acuity in preverbal children who are being treated for amblyopia.
authors.affiliation: Department of Ophthalmology, University of Iowa, Iowa City 52242.
authors.forename: R V
authors.initials: RV
authors.lastname: Keech
authors.forename: P J
authors.initials: PJ
authors.lastname: Kutschke
mesh_terms: D000550:Amblyopia / Q000175:diagnosis*; D002648:Child; D004867:Equipment Design; D005374:Filtration / Q000295:instrumentation / Q000379:methods*; D006801:Humans; D015203:Reproducibility of Results; D014787:Vision Tests; D014792:Visual Acuity