Veronica O'Dwyer:  Research

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Amblyopia is a condition of poor vision, which cannot be corrected by spectacles, and which is usually caused by developmental problems in the eye and brain during infancy.

This research is a psychophysical investigation of visual acuity in amblyopia. Three experiments have been carried out to date. The first experiment examined the effect of reduced illumination on visual acuity in anisometropic and strabismic amblyopes and defocused normals with a view to determining the acuity decrement with a neutral density filter, which is suggestive of organic amblyopia. The effect of chart type was examined in this experiment. The second experiment examined the differential effects of contrast and luminance on the acuity thresholds across the visual field in amblyopes. Resolution thresholds of Gabor patches were measured in the nasal and temporal visual field. The third experiment investigated the claim that positional acuity is selectively impaired in amblyopia. Resolution thresholds and vernier acuity were measured using identical psychophysical methods.

Two types of vernier thresholds were evaluated:

  • detection of vernier offset &
  • discrimination of the direction of vernier offset

These tasks were being examined centrally and in peripheral vision. The fourth experiment is currently being undertaken. Spatial filter models for hyperacuity in amblyopia are being examined. Vernier thresholds for a range of spatial frequencies are being measured in abutting and non-abutting stimuli of different phase offset. The results will be considered in relation to the filter model of vernier acuity.

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