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Virtual reality test may evaluate postural control in glaucoma population
A study evaluates a dynamic visual stimuli test to determine risk of falling among glaucoma patients.
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An evaluation model based on the assessment of postural reactivity using dynamic visual stimuli in a virtual reality environment may help evaluate balance control and associated risk of falling in patients with glaucoma, according to a study.
Patients with glaucoma have a more than three times greater risk of falling compared with healthy age-matched individuals.
“It is important that glaucoma patients, not necessarily only those with severe disease, be aware of this potential risk of increase in falling,” principal investigator Felipe A. Medeiros, MD, PhD, said.
Despite the association between glaucoma and falls, research to date has shown only a weak correlation between results obtained by conventional visual field testing and risk of falls in glaucoma patients. Medeiros and his group have developed a novel paradigm for testing that relies on a dynamic virtual reality environment to evaluate balance control.
“This new testing paradigm was shown to be much more effective than conventional perimetry or conventional balance assessment in predicting risk of falls in glaucoma patients,” he said.
Background
The cross-sectional study, published in Ophthalmology, evaluated the differences of postural reactivity between 42 patients with glaucoma vs. 38 healthy subjects. The subjects wore head-mounted stereoscopic goggles (Oculus Rift) while standing on a force platform. The goggles were used to present dynamic visual stimuli in an immersive virtual reality environment, whereas the force platform was able to capture the changes in posture that occurred in reaction to those stimuli.
Several different visual stimuli were presented, such as one simulating translational movement (as if the patient were moving through a tunnel) or rotational movement (as if the floor were spinning).
“What we did that is innovative was to simulate a virtual reality environment that was better able to represent the dynamics of how vision is used in everyday activities,” Medeiros said.
Results
During the translational and rotational stimuli, the researchers noted that the average overall standard deviation of the torque moments, a measure of postural pertubation, was approximately 30% to 40% greater in glaucoma patients compared with healthy subjects. This difference was more pronounced than that obtained when subjects were tested according to previously used testing paradigms.
In previous studies of postural balance in glaucoma, patients would either close both eyes or keep their eyes open and look at a static point, Medeiros said.
“What we found with these dynamic stimuli was that they were much more effective in inducing change in balance in glaucoma patients compared with the conventional approaches,” Medeiros said.
The researchers also obtained information about history of falls using a standardized questionnaire. Of the 80 total subjects, 32 had a history of falling in the previous year, and falling was significantly associated with the diagnosis of glaucoma (P = .001).
In the multivariate models, postural perturbations during translational and rotational stimuli were significantly associated with history of falls in glaucoma patients.
“The model including the new postural metrics performed significantly better than conventional testing in predicting history of falls,” Medeiros said.
Importantly, the model also adjusted for confounding factors such as age and gender, in addition to other non-visual contributors to balance control, such as those from the vestibular system and proprioception.
“The feedback we get from the muscles and the vestibular system help us stay in balance, so we had to also take that into account as potential confounding factors,” he said.
Ongoing process
In addition to the glaucoma population, Medeiros suggested that the postural control test using a virtual reality environment might potentially be used in other diseases that affect balance and increased risk of falls, such as macular degeneration.
“It will be very interesting to evaluate the role of this approach in these other conditions,” he said.
Data collection for the study continues.
“We think it is important to follow the patients over time, collecting longitudinal measurements with the new test and see how it’s able to predict the future occurrence of falls in this population,” Medeiros said. “This is going to be a very important study.” – by Kristie L. Kahl
- Reference: Diniz-Filho A, et al. Ophthalmology. 2015;doi:10.1016/j.ophtha.2015.02.010.
- For more information: Felipe A. Medeiros, MD, PhD, can be reached at Vision Performance Laboratory, Department of Ophthalmology, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0946; email: fmedeiros@ucsd.edu.
Disclosure: Medeiros reports no relevant financial disclosures.
Perspective
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William B. Trattler, MD
It is not uncommon to find out that a friend, family member or acquaintance older than age 65 years has fallen and broken a hip or suffered some form of trauma. Approximately one out of three adults older than age 65 will experience at least one fall per year, with many of these falls resulting in significant bodily injury. Not surprisingly, ocular conditions with vision loss are associated with an increased risk of fall. Patients with glaucoma have been found to have a threefold increase in the risk for fall compared with age-matched adults without glaucoma.
In this study, the researchers attempted to compare the balance of patients with and without glaucoma by placing them in a virtual reality environment and to measure their posture as well as their ability to maintain good posture during the testing. The researchers also collected data for each patient regarding the number (if any) of falls that he or she experienced. The study found that glaucoma patients were more likely to lose balance than the control subjects, and these findings were correlated with their past history of fall. Overall, the virtual reality environment used in this study may be effective at helping clinicians determine whether patients may be at an increased risk for experiencing a fall so that appropriate safety measures can be taken.
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