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.