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H. E. Bedell, D. N. Jackson, L. Gantz; Stereothresholds and Perceived Suprathreshold Depth During Image Motion in Normal Observers and Subjects With Infantile Nystagmus. Invest. Ophthalmol. Vis. Sci. 2010;51(13):4358.
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© ARVO (1962-2015); The Authors (2016-present)
Dioptric blur is known to elevate the stereothreshold and reduce perceived depth for targets with suprathreshold retinal image disparities. We asked whether motion blur, produced by rapid motion of the stereotarget or the eyes, exerts similar effects on the stereothreshold and perceived suprathreshold depth.
Near stereothresholds were measured for 10 normal observers using the Wirt rings of the Titmus stereotest during normal viewing, monocular image blur (+2.5 D), and repetitive 4-Hz motion of the targets seen by both eyes. In each of the above viewing conditions, observers also specified the magnitude of depth, in mm, that they perceived in the Titmus fly (3000" disparity) and the cat figure of the Lang stereo test (1200" disparity). For comparison, stereothresholds and the perceived depth in the Titmus Fly were determined for 6 non-strabismic observers with infantile nystagmus (IN).
In normal observers, both dioptric and motion blur produce a substantial elevation of the stereothreshold and an associated reduction of perceived suprathreshold depth (Fly: r = -0.78, r = -0.70; Cat: r = -0.56, r = -0.40 for optical blur and motion, respectively). A similar relationship between the stereothreshold and the magnitude of perceived suprathreshold depth was seen in observers with IN. Other conditions, such as monocular glare and reduced target luminance, elevate normal observers' stereothresholds and reduce the magnitude of perceived suprathreshold depth in the Titmus fly, but not the Lang cat.
Both dioptric and motion blur produce a similar relationship between the stereothreshold and the magnitude of perceived suprathreshold depth, suggesting that both types of blur have similar effects on disparity detection and encoding. Comparable results were observed when motion blur resulted from movement of the stereotarget or (in observers with IN) movement of the eyes. However, not all conditions that increase the stereothreshold reduce the magnitude of perceived depth, at least for targets with moderate suprathreshold disparities. Observers with poor stereopsis therefore may not exhibit an associated reduction of perceived suprathreshold depth.
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