What is the Nature of the Reach-and-Grasp Deficit in Glaucoma?

PReCIS:: In a reach-and-grasp task, patients with glaucoma exhibited a motor disorder, even when they had time to explore their environment. The motor performance of glaucoma patients should be taken into account in rehabilitation. PURPOSE Vision plays an important role in planning and executing manual prehension (reaching and grasping). We assess the impact of glaucoma on motor production, as a function of the visual exploration time available to the patients. METHODS We compared performance in 2 reach-and-grasp tasks determined by whether or not the participants (16 glaucoma patients, 14 age-matched and 18 young controls) had time to explore the objects before reaching and grasping a target object defined by its color. RESULTS Differences were observed between glaucoma patients and age-matched controls on movement duration and peak velocity (reaching phase) only when participants were not provided time to look at the objects before the movement (immediate condition). CONCLUSIONS Glaucoma patients exhibited a motor disorder (grasping phase) only when they had no time to explore their environment before performing the reach-and-grasp task. The motor abnormalities in reaching phase observed in glaucoma patients in previous studies seem to result from difficulties in target identification rather than from visuomotor deficits. From a clinical point of view, motor performances of glaucoma patients could be modulated by task, especially by temporal constraints of task.