title: [The F-L test for determining alternating central scotoma].
abstract: BACKGROUND
  Based on their experiences several authors consider an alternating central scotoma as the main reason for reading difficulties due to dyslexia.
  
  
  METHODS
  Searching for a simple and reliable method for determination of an alternating central scotoma we used a pair of synoptophore fusion images, in the center of which we added the letter F respectively L as central control signs. A spontaneously perceived and persisting E means a perfect and stable orthophoria. A persisting F or L with fusion of the images means a one sided central scotoma. Alternation of F and L with fusion of the images means an alternating central scotoma.
  
  
  RESULTS
  By examining normal readers, untreated asthenopic and untreated dyslexic patients, we found mostly rapid alternation of F and L in the latter two groups, whereas most of the normal readers saw F, L and E alternating at longer intervals.
  
  
  CONCLUSIONS
  Thus undisturbed reading seems not to demand perfect orthophoria. On the other hand a rapidly alternating central scotoma may be considered as an important factor causing reading difficulties.
authors.forename: D
authors.initials: D
authors.lastname: Safra
mesh_terms: D000293:Adolescent; D001248:Asthenopia / Q000175:diagnosis / Q000209:etiology; D001288:Attention; D002648:Child; D003118:Color Perception; D004410:Dyslexia / Q000175:diagnosis* / Q000209:etiology; D005260:Female; D006801:Humans; D008297:Male; D009949:Orientation; D010364:Pattern Recognition, Visual; D011932:Reading; D012607:Scotoma / Q000145:classification / Q000150:complications / Q000175:diagnosis*; D014787:Vision Tests