Glaucoma often is called “the sneak thief of sight” for good reason: Many people are unaware that glaucoma has few symptoms or warning signs in its early stages.
Early treatment for glaucoma can sometimes (but not always) slow the progression of the disease. However, as of yet, there is no cure for glaucoma and its resulting visual field loss, which can interfere with a wide range of everyday activities.
Visual field loss from glaucoma can create problems with moving safely through the environment, including indoor movement and outdoor travel. You can feel unsafe when crossing streets or become lost or disoriented, either inside your home or out in the community.
Now, researchers from the University of California San Diego have investigated the connection between visual field loss from glaucoma and difficulty with wayfinding (explained below) by creating an immersive visual reality environment to determine how people with glaucoma create (or have difficulty creating) a “mental map” to help with these everyday navigation tasks.
In addition to helping with navigation, this “visual mapping” research shows promise for (a) increasing the effectiveness of low vision exams and assessment, (b) teaching important visual skills, such as systematic scanning, and (c) contributing to safer and more efficient orientation and mobility skills.
From Investigative Ophthalmology & Visual Science
This new glaucoma and wayfinding (described below) research, titled Wayfinding and Glaucoma: A Virtual Reality Experiment, has been published as an open-source article in the July 17, 2017 issue of Investigative Ophthalmology & Visual Science, the official journal of the Association for Research in Vision and Ophthalmology (ARVO). ARVO is an international organization that encourages and assists research, training, and publication in vision and ophthalmology, including low vision.
The authors are Fábio B. Daga, Eduardo Macagno, Cory Stevenson, Ahmed Elhosseiny, Alberto Diniz-Filho, Erwin R. Boer, Jürgen Schulze, and Felipe A. Medeiros, from the University of California San Diego, La Jolla, California.
First, An Explanation of Terms Used in the Research
Here is a brief explanation of some key terms used in this glaucoma research:
- Allocentric: An allocentric frame of reference provides information about the location of an object as it relates to other objects in the environment, independently of the person’s own body.
- Egocentric: An egocentric frame of reference provides information about the location of an object as it relates to the person’s own body, such as left/right or up/down.
- Virtual reality: A computer-generated simulation of a three-dimensional environment that a person can interact with by using special electronic equipment, such as a helmet with a screen inside or gloves fitted with sensors.
- Wayfinding: The process of making and following a route between a beginning point and a destination.
About the Glaucoma Wayfinding Research
Edited and excerpted from the open-source article Wayfinding and Glaucoma: A Virtual Reality Experiment:
Wayfinding is the process of determining and following a path or route between an origin and a destination. As a process humans use to orient and navigate on foot or with a vehicle, wayfinding is an integral part of people’s daily life, occurring in many situations, such as walking inside a home or a building, navigating through a city, or driving across a country.
Wayfinding requires the proper encoding, processing, and retrieval of spatial information, and visual cues are often the main source in perceiving the environment. The purpose of this study was to investigate wayfinding behavior and spatial cognition in patients with glaucoma using a virtual reality (VR) environment, the Virtual Environment Human Navigation Task [called the VEHuNT in this research].
The study included 31 people with glaucoma and 20 subjects with unimpaired vision. In addition to vision and glaucoma testing, the subjects also completed the Montreal Cognitive Assessment Test (MoCA). The MoCA test is a screening tool developed to detect mild cognitive dysfunction.
The Virtual Reality Setup
The subjects sat at a table, wearing polarized glasses to see a 3-D image during testing, and navigated through the virtual environment using a steering wheel and an accelerator pedal. You can view the online virtual reality setup at the ARVO website.
The Virtual Rooms
Virtual Room A contained several visual cues: two large colored walls, two wall cues (paintings), and two floor cues (a chair and a plant, both located off to the side). Because Room A contained many different visual cues, it promoted an allocentric solution to the wayfinding problem and required creating a mental representation of the room, called a cognitive map.
An allocentric frame of reference provides information about the location of an object as it relates to other objects in the environment, independently of the person’s own body.
Virtual Room B contained only one visual cue, a chair near the center of the room. Because Room B contained only one central chair placed in a fixed spot, it promoted an egocentric solution to the wayfinding problem and did not require creating a cognitive map.
An egocentric frame of reference provides information about the location of an object as it relates to the person’s own body, such as left/right or up/down. You can view the two virtual rooms at the ARVO website.
The subjects were instructed to use the steering wheel to “drive” to a clearly indicated location in each one of the two virtual rooms (called the “visible target”), identified by a green cone on the floor. They were instructed to inspect the room and pay attention to the surroundings while “driving” to the target.
Additional trials required the subject to revisit the initial location, but the location was no longer visibly marked (called the “hidden target”). It only reappeared when the subject’s driving path intersected with the base of the green cone, which ended the trial.
In the study, glaucoma subjects performed significantly worse than healthy subjects in wayfinding tasks that promoted allocentric-based spatial reference [those in Room A] to successfully complete the task. This suggests that people with glaucoma may have difficulty building accurate representations of the spatial structure of an environment, in the presence of significant visual field loss.
Times to complete the wayfinding tasks were, on average, over 40% longer for glaucoma compared to healthy subjects for Room A. However, there was no significant difference between the groups for Room B.
Why These Results?
In order to successfully complete the task with the hidden target in Room A, the subject initially had to build an accurate mental representation of the spatial structure of the environment (called a cognitive map). The person would then have to use the cognitive map to guide him or her on how to navigate toward the hidden target.
Cognitive maps help to explain the spatial relationship between things in the world and can recognize places, compute distances and directions, and help a person find the way from where the subject is to where the subject wants to be in complex environments.
There is evidence that loss of peripheral vision may prevent building accurate cognitive maps. In our study, the loss of peripheral field in glaucoma patients may have made it difficult for them to build an accurate cognitive map of the virtual environment. This translated later into difficulties in performing the wayfinding tasks with hidden targets for Room A.
What Does This Mean?
Loss of peripheral vision may impede the ability to perform effective visual searches in the environment and attend to relevant objects. In addition, in the presence of significant peripheral vision loss, the visual information acquired … may not be coherent enough to allow an accurate representation of the location of objects in space relative to each other and the overall environment structure.
Virtual reality environments may represent a useful approach for assessing functional vision in patients and for clinical trials of emerging therapies in ophthalmology.
What Is Glaucoma and Visual Field Loss?
Glaucoma is a group of eye diseases that can lead to blindness by damaging the optic nerve, which transmits information from the eye to the brain, where it is processed and interpreted. The eye continuously produces a fluid, called the aqueous, that must drain from the eye to maintain healthy eye pressure. Glaucoma is particularly dangerous to your vision because there are usually no noticeable initial symptoms or early warning signs.
Glaucoma results in peripheral (or side) vision loss initially, and the effect can be like looking through a tube or into a narrow tunnel. This “tunnel vision” effect makes it difficult to walk without bumping into objects that are off to the side, near the head, or at foot level:
These are examples of peripheral vision loss, or a constricted visual field:
A living room viewed through a constricted visual field.
Source: Making Life More Livable. Used with permission.
The typical progression of vision loss from glaucoma
Source: National Eye Institute
Because glaucoma has no obvious initial symptoms, a comprehensive dilated eye exam is critical to detect early glaucoma changes. People who are over 40 should have a dilated eye examination from an ophthalmologist or optometrist at least every two years. African Americans; people who are over 35 and have a family history of glaucoma; and everyone age 60 or older should schedule a comprehensive eye examination every year.
You can learn more about glaucoma detection and treatment at How Can I Detect Glaucoma if There Are No Initial Symptoms?, What Are the Different Treatments for Glaucoma?, and Tips for Taking Glaucoma (and Other) Eye Drops at VisionAware.
More About the Glaucoma Wayfinding Research from Investigative Ophthalmology & Visual Science
Here is more information about the study, excerpted from the article Abstract, with the full open-source article available online:
Purpose: Wayfinding, the process of determining and following a route between an origin and a destination, is an integral part of everyday tasks. The purpose of this study was to investigate the impact of glaucomatous visual field loss on wayfinding behavior using an immersive virtual reality (VR) environment.
Methods: This cross-sectional study included 31 glaucomatous patients and 20 healthy subjects without evidence of overall cognitive impairment. Wayfinding experiments were modeled after the Morris water maze navigation task and conducted in an immersive virtual reality (VR) environment.
[Editor’s note: A cross-sectional study analyzes a group of people at one specific point in time, rather than study them over a longer period of time. In contrast, a longitudinal study follows, and gathers information about, the same individuals or group of people over an extended period of time.]
Two rooms were built varying only in the complexity of the visual scene in order to promote allocentric-based (room A, with multiple visual cues) versus egocentric-based (room B, with single visual cue) spatial representations of the environment. Wayfinding tasks in each room consisted of revisiting previously visible targets that subsequently became invisible.
Results: For room A, glaucoma patients spent on average 35.0 seconds to perform the wayfinding task, whereas healthy subjects spent an average of 24.4 seconds. [Note: This result was statistically significant.] For room B, no statistically significant difference was seen on average time to complete the task.
Conclusions: Glaucoma patients performed significantly worse on allocentric-based wayfinding tasks conducted in a virtual reality environment, suggesting visual field loss may affect the construction of spatial cognitive maps relevant to successful wayfinding. Virtual reality environments may represent a useful approach for assessing functional vision endpoints for clinical trials of emerging therapies in ophthalmology.
- Organizing and Modifying Your Home
- Follow glaucoma research on the VisionAware blog.
- For patient-centered information about glaucoma detection, treatment, and everyday management, see VisionAware’s Patient’s Guide to Living with Glaucoma and Guía del Paciente: Vivir con Glaucoma.
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