Mobility-Related Gaze Training in Individuals With Glaucoma: A Proof-of-Concept Study.

PURPOSE: Older adults with glaucoma show inappropriate gaze strategies during routine mobility tasks. Furthermore, glaucoma is a risk factor for falling and colliding with objects when walking. However, effective interventions to rectify these strategies and prevent these adverse events are scarce. We designed a gaze training program with the goal of providing proof-of-concept that we could modify mobility-related gaze behavior in this population. METHODS: A total of 13 individuals with moderate glaucoma participated in this study. We taught participants general and task-specific gaze strategies over two 1-hour sessions. To determine the efficacy of this gaze training program, participants performed walking tasks that required accurate foot placement onto targets and circumventing obstacles before and after training. We used a mobile eye tracker to quantify gaze and a motion-capture system to quantify body movement. RESULTS: After training, we found changes in the timing between gaze shifts away from targets relative to stepping on them (P < 0.05). In the obstacle negotiation task, we found a greater range of gaze shifts early in walking trials and changes in the timing between gaze shifts away from obstacles after training (P < 0.05), each suggesting better route planning. A posttraining reduction in foot-placement error and obstacle collisions accompanied these changes (P < 0.05). CONCLUSIONS: Our results demonstrated that it is possible to modify mobility-related gaze behavior and mobility performance in older adults with glaucoma. TRANSLATIONAL RELEVANCE: This study provides proof-of-concept for a gaze training program for glaucoma. A larger, randomized controlled trial is warranted.

Glaucoma-Related Differences in Gaze Behavior When Negotiating Obstacles.

PURPOSE: Safe navigation requires avoiding objects. Visual field loss may affect how one visually samples the environment, and may thus contribute to bumping into objects and falls. We tested the hypothesis that gaze strategies and the number of collisions differ between people with glaucoma and normally sighted controls when navigating around obstacles, particularly under multitasking situations. METHODS: Twenty persons with moderate-severe glaucoma and 20 normally sighted controls walked around a series of irregularly spaced vertical obstacles under the following three conditions: walking with obstacles only, walking and counting backward to simulate a conversation, and walking while performing a concurrent visual search task to simulate locating a landmark. We quantified gaze patterns and the number of obstacle contacts. RESULTS: Compared with controls, people with glaucoma directed gaze closer to their current position (P < 0.05). They also directed a larger proportion of fixations (in terms of number and duration) to obstacles (P < 0.05). Despite this finding, considerably more people with glaucoma contacted an obstacle (P < 0.05). Multitasking led to changes in gaze behavior in both groups, and this was accompanied by a large increase in obstacle contacts among those with glaucoma (P < 0.05). CONCLUSIONS: Glaucoma alters gaze patterns when negotiating a series of obstacles and increases the likelihood of collisions. Multitasking in this situation exacerbates these changes. TRANSLATIONAL RELEVANCE: Understanding glaucoma-related changes in gaze behavior during walking in cluttered environments may provide critical insight for orientation and mobility specialists and guide the design of gaze training interventions to improve mobility.

Coordination of Gaze Behavior and Foot Placement During Walking in Persons With Glaucoma.

PURPOSE: Vision normally provides environmental information necessary to direct the foot to safe locations during walking. Peripheral visual field loss limits what a person can see, and may alter how a person visually samples the environment. Here we tested the hypothesis that the spatial-temporal coupling between gaze and stepping in a precision-based walking task is altered in persons with glaucoma, particularly under dual task situations, and results in reduced foot-placement accuracy. METHODS: Twenty persons with glaucoma and 20 normally sighted controls performed a precision walking task that involved stepping to the center of 4 targets under 3 conditions: targets only, walking, and counting backwards to simulate a conversation, and walking while performing a concurrent visual search task to simulate locating a landmark. We quantified foot-placement error and error variability with respect to the targets, as well as saccade and fixation timing with respect to foot placement. RESULTS: Compared with controls, persons with glaucoma looked earlier at future stepping targets (with respect to toe-off of the foot) in the targets only and count conditions, and transferred gaze away sooner from the current stepping target in all conditions (P<0.05). Persons with glaucoma also had increased foot-placement error, particularly in the count condition, and increased foot-placement error variability compared with normally sighted controls (P<0.05). CONCLUSIONS: Glaucoma significantly disrupts gaze-foot coordination and results in less accurate foot placement when precision is required during walking. This may increase the risk of trips and falls in this population.

Effect of ambient light and age-related macular degeneration on precision walking.

PURPOSE: To determine how age-related macular degeneration (AMD) and changes in ambient light affect the control of foot placement while walking. METHODS: Ten older adults with AMD and 11 normal-sighted controls performed a precision walking task under normal (∼600 lx), dim (∼0.7 lx), and after a sudden reduction (∼600 to 0.7 lx) of light. The precision walking task involved subjects walking and stepping to the center of a series of irregularly spaced, low-contrast targets. Habitual visual acuity and contrast sensitivity and visual field function were also assessed. RESULTS: There were no differences between groups when performing the walking task in normal light (p > 0.05). In reduced lighting, older adults with AMD were less accurate and more variable when stepping across the targets compared to controls (p < 0.05). A sudden reduction of light proved the most challenging for this population. In the AMD group, contrast sensitivity and visual acuity were not significantly correlated with walking performance. Visual field thresholds in the AMD group were only associated with greater foot placement error and variability in the dim light walking condition (r = -0.69 to -0.87, p < 0.05). CONCLUSIONS: While walking performance is similar between groups in normal light, poor ambient lighting results in decreased foot placement accuracy in older adults with AMD. Improper foot placement while walking can lead to a fall and possible injury. Thus, to improve the mobility of those with AMD, strategies to enhance the environment in reduced lighting situations are necessary.

Effects of age-related macular degeneration and ambient light on curb negotiation.

PURPOSE: To determine how age-related macular degeneration (AMD) and changes in ambient light affect the ability to negotiate a curb while walking. METHODS: Ten older adults with AMD and 11 normal-sighted control subjects performed a curb negotiation task under normal light (∼600 lux), dim light (∼0.7 lux), and following a sudden reduction (∼600 to 0.7 lux) of light. In this task, subjects walked and stepped up or down a simulated sidewalk curb. Movement kinematics and ground reaction forces were measured during curb ascent and descent. Habitual visual acuity, contrast sensitivity, and visual fields were also assessed. RESULTS: Apart from slower gait speed in those with AMD, there were no differences between groups during curb ascent for any other measure. During curb descent, older adults with AMD frequently used shuffling steps in the approach phase to locate the curb edge and showed prolonged double support duration stepping over the curb compared with control subjects. However, reduced lighting, particularly a sudden reduction, led to several significant changes in movement characteristics in both groups. For instance, toe clearance stepping up the curb was greater, and landing force stepping down was reduced. In addition, slower gait speed and greater double support duration were evident in curb ascent and descent. In AMD subjects, contrast sensitivity, visual acuity, and visual field threshold were associated with several kinematic measures in the three light conditions during curb negotiation. CONCLUSIONS: Minor AMD-specific changes in movement are seen during curb negotiation. However, attenuated lighting greatly impacts curb ascent and descent, regardless of eye disease, which manifests as a cautious walking strategy and may increase the risk of falling. Environmental enhancements that reduce the deleterious effects of poor lighting are required to improve mobility and quality of life of older adults, particularly those with AMD.

Tolerability and effectiveness of preservative-free dorzolamide-timolol (preservative-free COSOPT) in patients with open-angle glaucoma or ocular hypertension.

PURPOSE: To assess the effect of preservative-free dorzolamide-timolol on nonvisual symptoms and intraocular pressure (IOP) in newly diagnosed and untreated patients with open-angle glaucoma or ocular hypertension. METHODS: This was a prospective, 8-week, open-label, Canadian multicenter study. All patients were treated with preservative-free dorzolamide-timolol formulation. The primary outcome was the change in the nonvisual symptom score of the Glaucoma Symptom Scale (GSS-SYMP-6) from baseline to 8 weeks. Secondary effectiveness outcome measures were absolute and percent changes in IOP from baseline to 4 and 8 weeks. RESULTS: One hundred and seventy-eight patients were enrolled. Mean (SD) age was 65.6 (12.1) years and 90 (50.6%) were females. There were 92 patients diagnosed with open-angle glaucoma, 62 with ocular hypertension, and 23 with both diseases (diagnosis was missing for one patient). The mean (SD) GSS-SYMP-6 score increased from 73.6 (21.8) at baseline to 76.1 (20.7) at 8 weeks (P = 0.097). Mean (SD) IOP significantly decreased by 11.7 (5.1) mmHg at 4 weeks (P < 0.001) and by 11.5 (5.3) mmHg at 8 weeks (P < 0.001), representing reductions of -38.5% (P < 0.001) and -38.0% (P < 0.001), respectively. CONCLUSION: Preservative-free dorzolamide-timolol does not increase eye discomfort while significantly reducing IOP in patients with open-angle glaucoma or ocular-hypertension.