The functional consequences of glaucoma for eye-hand coordination.

PURPOSE To examine whether patients with glaucoma exhibit differences in visually guided reaching-and-grasping (prehension) behavior compared with normally sighted control subjects. METHODS Sixteen patients with glaucoma and 16 control subjects with no ocular disease participated. Participants were required to reach out and precision grasp one of two cylindrical objects placed on a table top in front of them in laboratory conditions in three viewing conditions (binocular, right eye alone, left eye alone). Lightweight reflective markers were placed on the subject's preferred hand for recording its movement in three-dimensional space. Three motion capture units recorded the motion of these markers as the subjects reached out and precision grasped household objects. Various indices of prehension planning, execution, and control were quantified. Visual fields (VF) were measured using standard automated perimetry generating monocular mean deviation (MD) scores. Binocular VF sensitivity was estimated by using the integrated visual field (IVF). Stereoacuity was measured with the Frisby stereoacuity test. Significant differences in prehension movement between patients and control subjects in each viewing condition were investigated, and associations between prehension kinematics and VF sensitivity were examined. RESULTS The patients and control subjects were of a similar age (median [range]: patient group, 72.2 years [62.5-86.9]; control group, 69.0 years [64.3-78.3]). The patient group had asymmetrical disease and relatively minor binocular overlapping defects (better eye MD, -5.7 dB [-16.7 to +0.45 dB]; worse eye MD, -11.8 dB [-29.3 to -1.5 dB]; IVF score, 3 [0-36]). They exhibited slightly poorer stereoacuity levels than did the control subjects (patient group, 55 sec arc [40-110]; control group, 40 sec arc [20-80; Mann-Whitney U test, P < 0.05]). They also showed statistically significant delays in average movement onset (MO: approximately 100 ms delay, Mann-Whitney U test P < 0.0001) and overall movement time (OMD: approximately 140 ms delay; Mann-Whitney U test P < 0.05), suggesting impairments in initial movement planning and control. Deficits were exhibited in the reaching component, with data suggesting that glaucomatous patients made more tentative movements when reaching for the object. These deficits correlated with both increasing severity of VF defect and impaired stereoacuity. There were no differences in grasping characteristics between patients and control subjects in this sample. CONCLUSIONS This study provides evidence that patients with glaucoma exhibit deficits in eye-hand coordination compared with the age-matched normally sighted control. Further study is needed to assess the specific effect of field loss location on prehension kinematics.