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Biomedical subjects

S C Rawlings

Publications and source records attributed to S C Rawlings.

7 recordsLinked to original sources
PubMed1980

Evaluation of clinical stereoacuity tests.

Sixty children ages two to seven were separated into two age-matched groups of thirty each, one consisting of a group of normal children, and the other a strabismic-anisometropic group. All subjects were examined with four currently available stereoacuity tests, the RDE, Randot, Titmus, and the TNO. Significant differences in performance were found between the two groups. Across all tests there was a 10 to 17% over-referral rate and a 33-37% under-referral rate. Untestability in the normal group ranged from 3.3-6.7% across tests, while in the patient group it ranged from 3.3-20.0%. The under-referral rate is unacceptable and casts doubt on the value of our present stereoacuity tests in screening for subtle defects in binocular function in the young child.

Amblyopia↗
PubMed1979

Dynamic depth reversal stereograms.

A new stimulus was generated to create dynamic stereopsis. Binocular disparity was alternated between crossed and uncrossed conditions, while mean luminance remained constant, to produce a stereoscopic stimulus that appeared to move continuously in depth. These dynamic depth reversal stereograms provided an effective stimulus to elicit the visual evoked potential (VEP). Neural coding of stereopsis was reflected in the cortical response with VEP amplitudes changing as a function of binocular disparity and of image blur in the stereograms.

Child↗
PubMed1977

Viewing time and stereoscopic threshold with random-dot stereograms.

The effect of viewing time on the threshold for depth and form discrimination using random-dot stereograms has been investigated. For 12 subjects the relation between logarithm of threshold disparity and logarithm of viewing time was linear for both depth and form discrimination, but the threshold for form discrimination was approximately twice the threshold for depth discrimination. Stereo thresholds determined with random-dot stereograms were not significantly related to stereo thresholds measured with a Howard-Dolman apparatus.

Depth Perception↗
PubMed1975

Pattern and depth discrimination from random dot stereograms.

The discrimination of depth and pattern was investigated using random dot stereograms. For all four subjects, the psychometric function for depth judgments (probability of correct response) was clearly superior to pattern judgments over a range of ten crossed or uncrossed binocular disparity values. Degrading the visual images, either monocularly or binocularly, with various convex lens power (fogging lenses) reduced both depth and pattern discrimination across all disparity values, rather than simply increasing the thresholds. The results are discussed with reference to current theories of stereopsis, and the question of the hierarchial processing of depth and pattern information is considered.

Animals↗