Visual optic flow processing for posture and 3D shape perception in primary open angle glaucoma
The processing of large field visual information is an important pre-requisite for our daily activities, such as walking and driving. Indeed, it has been recognized that the processing of large field visual motion (optic flow) information is critical for postural control and 3-dimensional (3D) shape perception. Histopathological and psychophysical studies support the view that primary open angle glaucoma (POAG) preferentially damages the magnocellular (M) pathway. As motion perception relies heavily on the M pathway, it follows that POAG should result in significant behavioural deficits for tasks such as maintaining posture and perceiving the shape of 3D objects. To investigate this further, two experiments were performed. First, the postural stability was measured in the standing subjects and the effect of vision on stabilization was analyzed in POAG and normal subjects. Second, the ability to perceive the 3D shape of objects in large field vision from motion parallax (MP) versus static texture (ST) cues was assessed by using computer-generated surfaces that were presented at various eccentricities (central field or peripheral field). It was found that postural stabilization is significantly decreased in POAG, possibly prior to the diagnosis of glaucoma. Also the perception of 3D shape from MP and ST cues is significantly impaired. This impairment is uniform for ST cues, but affects more specifically the peripheral field for MP cues. The results indicate an early loss in motion-based performance (posture, 3D perception) that follows the peripheral/central vision imbalance a characteristic of POAG. Hence the results support the hypothesis of preferential M losses in glaucoma, and point to the need for preventive actions against risks during locomotion (staircase descent) or driving, in the follow up of POAG patients.
primary open angle glaucoma, visual optic flow, postural stabilization, 3D shape perception, motion parallax cue, static texture cue.
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