Accommodation to large disparity stereograms.
OBJECTIVE
The purpose of this study was to test whether observers would show accommodation changes to depth depicted in large disparity stereograms and whether the amount of accommodation was related to the amount of depth seen in the stereograms. Previous studies have shown small accommodation changes to depth depicted in stereograms. We tested a larger range of depths than previously investigated and also asked observers to judge the depth depicted in the stereogram, because a previous study had suggested that this might be an important factor.


METHODS
All our observers had emmetropia. Accommodation was measured with a Canon Autoref R-1autorefractor as an observer viewed a depthful 4-by-4 cm planar target set against a 20-by-20 cm planar background 57 cm from the observer. The target was presented at a range of depths, -8 to +8 cm, either in stereogram stimuli or real stimuli. Each observer also made depth judgments of stereogram targets, after training with real targets. We also recorded the time taken for each observer to discern the depicted depths in stereograms.


RESULTS
The accommodation shown by all observers (n = 9) to stereogram targets was significant but was on average about 60% of that predicted. There were individual differences in the accommodation an observer showed to stereogram targets, but this was not related to the amount of depth the observer saw in the stereogram.


CONCLUSIONS
Accommodation changes did occur to stereogram targets, but these were generally less than predicted and also less than those shown for real targets. Possible reasons for these findings and the implications for the use of stereograms in clinical tests are discussed.
Davis
Helen
H
Academic Unit of Ophthalmology and Orthoptics, Medical School, and the Department of Psychology, University of Sheffield, Sheffield, United Kingdom. h.davis@sheffield.ac.uk
Buckley
David
D
Jacobs
Ruth E G
RE
Brennand
David A A
DA
Frisby
John P
JP
D000065:Accommodation, Ocular / Q000502:physiology*; D000328:Adult; D003867:Depth Perception / Q000502:physiology*; D003941:Diagnostic Techniques, Ophthalmological / Q000295:instrumentation*; D005260:Female; D006801:Humans; D008297:Male; D010780:Photogrammetry / Q000379:methods