title: New rarebit vision test captures macular deficits hidden to acuity tests.
abstract: OBJECTIVE
  Evaluation of a new personal-computer-based vision test aimed for rapid and accurate assessment of macular conditions such as age-related macular degeneration (AMD).
  
  
  METHODS
  The new test depends on segmented digits defined by rarebits, that is, receptive field-size bright dots briefly presented against a dark background. Digit size was fixed at 40 × 50 min of arc. Digit positions were varied at random within a 4.6 × 3.5-degree test field. There were no fixation demands. The number of rarebits per digit segment could be varied between 3 (the minimum needed for veridical perception) and 128, in 11 preset steps. The test task was to find the smallest rarebit number required to recognize the test digits. Thirty-seven patients with various stages of AMD and 25 control subjects participated in the evaluation, which also included a standard acuity test.
  
  
  RESULTS
  Analysis of receiver operating characteristics indicated significantly better discrimination by the rarebit test. Rarebit numbers >16 appeared to reliably indicate the presence of oedema.
  
  
  CONCLUSIONS
  The rarebit test appeared well suited for fine grading of vision in AMD. The simple set-up and the lack of fixation demands made for practicable examinations of short durations. The test is available for free on the Internet.
authors.affiliation: Department of Clinical Neuroscience and Rehabilitation, Institute of Neuroscience and Physiology, The Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden.
authors.forename: Christina
authors.initials: C
authors.lastname: Winther
authors.affiliation: Department of Clinical Neuroscience and Rehabilitation, Institute of Neuroscience and Physiology, The Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden.
authors.forename: Lars
authors.initials: L
authors.lastname: Frisén
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D005451:Fluorescein Angiography; D057092:Geographic Atrophy / Q000145:classification / Q000175:diagnosis*; D006801:Humans; D008269:Macular Edema / Q000175:diagnosis*; D008297:Male; D008875:Middle Aged; D012372:ROC Curve; D015203:Reproducibility of Results; D012160:Retina / Q000473:pathology*; D041623:Tomography, Optical Coherence; D014787:Vision Tests / Q000379:methods*; D014792:Visual Acuity; D057135:Wet Macular Degeneration / Q000145:classification / Q000175:diagnosis*
keywords: age-related macular degeneration; macula; macular oedema; rarebit; vision test; visual acuity