Objective estimation of visual acuity with preferential looking

Invest Ophthalmol Vis Sci. 2011 Feb 3;52(2):708-13. doi: 10.1167/iovs.09-4911.


Purpose: A novel preferential looking (PL) procedure that uses quantitative analysis of visual scanning parameters is presented.

Methods: Nine adult subjects were presented with a set of 14 visual stimuli (stimuli included three uniform gray fields and one field with black-and-white square wave gratings) spanning the range of spatial frequencies from 1.5 cyc/deg to 35.1 cyc/deg (1.3 logMAR to -0.07 logMAR). A remote gaze-tracking system was used to monitor the subject's eye movements and the relative fixation time (RFT) on the grating target. Subsequently, a four alternative forced-choice psychophysical test (4AFC) was performed with the same visual stimuli.

Results: For visual stimuli for which the gratings' positions in the 4AFC test were identified correctly in 100% of the trials (reliably discriminated), the mean RFT was 72.5% ± 9.0%. For stimuli for which the spatial frequencies were higher than the subject's psychophysically determined visual acuity (VA) threshold (nondiscriminated), the mean RFT was 25.3% ± 8.5%. Using three repeated trials at each spatial frequency and a VA detector based on the conditional probability density functions of the RFT, the average VA was underestimated by 0.06 logMAR (range, 0.00-0.20 logMAR).

Conclusions: In adults, automated quantitative analysis of visual scanning patterns can be used to estimate VA objectively and rapidly (210 seconds) with a mean error of 0.06 logMAR. The novel approach may form the basis for PL procedures that are more objective and more accurate than the traditional clinical PL procedures.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Choice Behavior
  • Eye Movements / physiology
  • Female
  • Fixation, Ocular / physiology
  • Humans
  • Male
  • Vision Tests / instrumentation
  • Vision Tests / methods*
  • Visual Acuity / physiology*
  • Young Adult