title: Frosted cylindrical lens induced artefact on Humphrey automated perimetry.
abstract: BACKGROUND
  The aim of this study was to assess the effect of a cylindrical corrective lens with frosted sides on Humphrey automated perimetry performed with a translucent spectacle occluder in the contralateral eye.
  
  
  METHODS
  Ten healthy volunteers with cylindrical refractive errors of more than 1.50 DC had Humphrey visual fields (30-2) measured with the contralateral eye occluded with either a translucent spectacle occluder or an opaque patch. The order of testing with each occluder was randomised. Additionally, visual field examination with the opaque patch was performed on three volunteer subjects with deep-set eyes to establish the clinical significance of the frosted cylindrical lens induced artefact (CLA). The back vertex distances for the correcting lenses were measured for all tests.
  
  
  RESULTS
  Eight out of 10 volunteers tested with the translucent occluder demonstrated CLA, which was absent when the opaque patch was used. The presence of an artefact corresponding to the axis of the cylinder was observed, when the vertex distance was more than 15 mm. Three subjects with deep-set eyes presented with CLA, even with the use of an opaque patch.
  
  
  CONCLUSIONS
  Cylindrical lens artefacts can occur with increasing vertex distance when using a translucent spectacle occluder instead of an opaque patch. CLA is also seen in subjects with deep-set eyes.
authors.affiliation: Medical and Vision Research Foundation, Sankara Nethralaya, Chennai, India.
authors.forename: V
authors.initials: V
authors.lastname: Sreenivasan
authors.forename: S
authors.initials: S
authors.lastname: Ve Ramesh
authors.forename: Ronnie
authors.initials: R
authors.lastname: George
authors.forename: M
authors.initials: M
authors.lastname: Baskaran
mesh_terms: D016477:Artifacts; D004867:Equipment Design; D005139:Eyeglasses; D006801:Humans; D012029:Refraction, Ocular; D012030:Refractive Errors / Q000503:physiopathology / Q000628:therapy*; D012683:Sensory Deprivation; D058609:Visual Field Tests / Q000379:methods*; D014794:Visual Fields / Q000502:physiology*