Study examines navigation performance in glaucoma with virtual-reality-based assessment of path integration
Uncertainty during everyday navigation tasks may adversely affect quality of life for patients with glaucoma
Interestingly, researchers found that travel-time duration correlated inversely with pRNFL thickness. Image credit: ©Rawpixel.com – stock.adobe.com
A team of researchers has investigated the relationship between visual impairment in glaucoma and path-integration-based navigation.
The observational study was published in Scientific Reports.1 The research was conducted in a collaboration of the Ophthalmic Department of Otto-von-Guericke University of Magdeburg and the German Center for Neurogenerative Diseases (DZNE), Magdeburg, after the approval of the local ethical committee of the Otto-von-Guericke University of Magdeburg, Germany, adhering to Declaration of Helsinki guidelines. Study participants gave written informed consent.1
In the study, 14 patients with glaucoma and 15 controls underwent ophthalmological examination (including visual acuity (logMAR), visual field sensitivity (MD: mean deviation from matched reference cohort), and peripapillary retinal nerve fiber layer (pRNFL)).
Both groups navigated physically in virtual reality (VR) environments during daylight and dawn conditions.
“We quantitatively assessed the performance of participants in the path-integration task using three different outcome measures, travel-time, pointing-time and Euclidian-distance error,” the researchers wrote.
Robust linear regression was conducted between visual function outcomes of the better eye and VR outcome measures.1
Patients with glaucoma showed increase in travel-time (by 8.2 ± 1.7 s; p = 0.002) and in pointing-time (by 5.3 ± 1.6 s; p = 0.016). Predictors were MD for all outcome measures (p < 0.01) and pRNFL for travel-time (p < 0.01).
In the study, the researchers assessed the navigation performance of glaucoma using path-integration paradigm in VR considering both cognitive-based and mobility-based skills employed in navigation. The researchers found that travel-time duration correlated inversely with pRNFL thickness.
This is of particular interest, as this OCT-based measure is an objective marker of glaucoma damage within the retina. “Our finding therefore, appears to offer an intriguing link between retinal damage and higher-level behavior that deserves attention in further research,” they noted.
The researchers noted that there are several limitations in their study that might deserve consideration.
“One limitation is that we only tested central vision,” they wrote. “The participants could only use the central visual field to complete the task in VR via the HMD, i.e. HTC Vive Pro, where the participants’ visual fields covered 47° and 40° temporal and nasal from fixation, respectively.”
They pointed out that in order to understand the effect of peripheral visual loss in path integration, an HMD with bigger field of view to show the stimuli might be of benefit. However, due to current stage of the VR technology, there has not been any HMD developed to fully cover the peripheral visual field.
Another limitation, according to the researchers, is linked to the difficulty of luminance calibration for the two lighting conditions (daylight vs dawn) for HMDs.1
“It should be noted that VR-setups bear a risk of cybersickness in general, but less likely in walking-based techniques in VR,” they wrote. Moreover, the cohorts were small (GLA = 14, C = 15) in the present proof-of-concept study due to restrictive inclusion criteria.
“Our GLA included mainly early and few advanced glaucoma cases,” the researchers noted.
However, the results suggest that the effect of glaucoma on the elapsed time depends on disease progression, i.e. people with stronger visual impairment need more time. This uncertainty during everyday navigation tasks may adversely affect their quality of life.1
“We found that our results correspond to previous navigation studies in real life and extended the knowledge by uncovering a relationship to objective, i.e. OCT, measures of glaucoma progression,” the researchers concluded in the study. “Therefore, applying VR tools to study navigation performance in greater sample of glaucoma participant in simulated real-life environments offer a promising opportunity understand the relationship between the glaucoma progression and cognitive task performance.”
