Resolving the clinical acuity categories "hand motion" and "counting fingers" using the Freiburg Visual Acuity Test (FrACT)

Graefes Arch Clin Exp Ophthalmol. 2009 Jan;247(1):137-42. doi: 10.1007/s00417-008-0926-0. Epub 2008 Sep 3.


Purpose: The Freiburg Visual Acuity Test (FrACT) has been suggested as a promising test for quantifying the visual acuity (VA) of patients with very low vision, a condition often classified using the semi-quantitative clinical scale "counting fingers" (CF), "hand motion" (HM), "light perception" (LP) and "no light perception". The present study was designed to assess FrACT performance in a sizable number of CF, HM, and LP patients in order to generate a setting for future clinical studies in the low vision range.

Methods: We examined a total of 41 patients (LP, n = 11; CF, n = 15; HM, n = 15) with various eye diseases (e.g., diabetic retinopathy, ARMD), covering the clinical VA scale from LP to CF. The FrACT optotypes were presented at a distance of 50 cm on a 17-inch LCD monitor with four random orientations. After training, two FrACT measurements (test and retest) were taken, each comprising 30 trials.

Results: FrACT measures reproducibly the VA of CF and HM patients. In CF patients, FrACT resulted in a mean logMAR = 1.98 +/- 0.24 (corresponding to a decimal VA of 0.010), for HM in a mean logMAR = 2.28 +/- 0.15 (corresponding to a decimal VA of 0.0052). In all LP patients the FrACT values were close to what would be obtained by random guessing. The mean test-retest 95% confidence interval was 0.21 logMAR for CF patients and 0.31 logMAR for HM respectively. Test-retest variability declined from 24 to 30 trials, showing that at least 30 trials are necessary.

Conclusion: FrACT can reproducibly quantify VA in the CF and HM range. We observed a floor effect for LP, and it was not quantifiable further. Quantitative VA measures are thus obtainable in the very low-vision range using FrACT.

Publication types

  • Clinical Trial
  • Validation Study

MeSH terms

  • Adult
  • Aged
  • Aged, 80 and over
  • Eye Diseases / diagnosis*
  • Form Perception
  • Humans
  • Middle Aged
  • Models, Statistical
  • Motion Perception
  • Psychophysics
  • Reproducibility of Results
  • Vision Tests / methods*
  • Vision Tests / standards*
  • Vision, Low / diagnosis*
  • Visual Acuity*
  • Young Adult