Natural statistics of depth edges modulate perceptual stability.

Binocular fusion relies on matching points in the two eyes that correspond to the same physical feature in the world; however, not all world features are binocularly visible. Near depth edges, some regions of a scene are often visible to only one eye (so-called half occlusions). Accurate detection of these monocularly visible regions is likely to be important for stable visual perception. If monocular regions are not detected as such, the visual system may attempt to binocularly fuse non-corresponding points, which can result in unstable percepts. We investigated the hypothesis that the visual system capitalizes on statistical regularities associated with depth edges in natural scenes to aid binocular fusion and facilitate perceptual stability. By sampling from a large set of stereoscopic natural images with co-registered distance information, we found evidence that monocularly visible regions near depth edges primarily result from background occlusions. Accordingly, monocular regions tended to be more visually similar to the adjacent binocularly visible background region than to the adjacent binocularly visible foreground. Consistent with our hypothesis, perceptual experiments showed that perception tended to be more stable when the image properties of the depth edge were statistically more likely given the probability of occurrence in natural scenes (i.e., when monocular regions were more visually similar to the binocular background). The generality of these results was supported by a parametric study with simulated environments. Exploiting regularities in natural environments may allow the visual system to facilitate fusion and perceptual stability when both binocular and monocular regions are visible.

Clinical Evaluation of the Articulinx Intercarpometacarpal Cushion for the First CMC Joint: A Feasibility Study.

Background The Intercarpometacarpal Cushion (ICMC; Articulinx, Cupertino, CA, USA) is an implantable spacer designed as a less invasive surgical treatment for osteoarthritis (OA) of the first carpometacarpal joint (CMC-1). Description of Technique Following local anesthesia and exposure of the joint capsule the ICMC, attached to a needle and suture tethers, is guided into the joint space under fluoroscopic visualization through a dorsal approach. The needle is pulled through the thenar eminence to the opposite side of the hand and, once proper device placement is confirmed, cut free and the joint capsule closed. Patients and Methods Eight female patients (median age 56 years; range, 42-83) were treated and followed for 6 to 24 months. Safety of the implant procedure was evaluated intraoperatively. Pain, joint function, and strength were evaluated at 6 weeks, 3, 6, 12 and 24 months with a Visual Analog Scale (VAS) for pain, the QuickDASH inventory, Canadian Occupational Performance Measure (COPM), and pinch and grip strength measurements. Results At 2 years (n = 6), mean VAS pain scores decreased from 6.3 (± 1.5) to 2.2 (± 1.1) (p < 0.001), mean QuickDASH scores improved from 47 (± 15) to 31 (± 11) (p < 0.10), mean COPM performance scores improved from 5.0 (± 1.2) to 5.5 ( ± 1.3) (p = NS). Mean pinch and grip strength measurements also improved compared with baseline. No serious adverse events occurred. Two device removals occurred, associated with a traumatic event and Stage IV OA with device displacement, at 6 and 9 months respectively. Conclusion The ICMC can be implanted safely. Effectiveness needs to be confirmed in future studies.