The presentation and subsequent treatment of strabismus and amblyopia have left many optometrists with an uncomfortable feeling. Virtual reality (VR) is a promising new approach to treatment that patients are embracing.
Traditional treatment methods for strabismus and amblyopia have been overwhelming and hard work for both the client and the therapist. It is easy to lose clients to follow up or find poor levels of compliance in treatment.1 It can also be challenging to define the outcomes one is aiming for as an optometrist. Are we working towards stereopsis, equal acuity, stability under accommodative pressure, elimination of suppression or the amount of the eye turn, or a good range of vergence skills? How do we balance outcomes with the needs of parents who may desire something unrealistic, such as straight eyes and for their child to be glasses-free?
Reinforcement with home vision therapy is what appears to yield the most improvement to outcomes
To date, our treatment protocols have been fairly static with patching, refractive correction, therapy and the use of monocular fixation in a binocular field (MFBF). And yet, our clients are open to technology and actually want their optometrist to recommend the latest treatments for them. A study from 2018 found that clients want three things from their health professional – greater empowerment, greater convenience and improved outcomes.2
VR AND OUR CLIENTS
Virtual reality (VR) is a new tool for optometry that addresses and solves many of the pain points that come with traditional treatment of strabismus and amblyopia. It is a tool that clients are willing to use, and even though it is early stages, it appears to be extremely effective.
In our practice at RA Optometrists in North Brisbane, the use of VR has resulted in a “WOW” experience from our clients of all ages. Adults are seeing in 3D for the first time in their memorable lives, which is proving to be more meaningful than we had expected. Noticing the depth of shoes lined up in a shoe store, or the depth of the bark on a paperbark tree, noticing their side mirrors while driving, are all aspects of vision we take for granted when our stereopsis has always been with us.
Yet VR is not altogether new – it is also being used among allied health professionals to treat conditions such as phobias, post-traumatic stress, pain, balance, and movement rehabilitation.
Because VR automatically engages the visual system, it makes sense that optometrists should be well versed in using this technology for our own clients. Indeed, we are well placed to be at the forefront of understanding why work on the visual system has such powerful effects on human perception and sense of self.
VR AND STRABISMUS /AMBLYOPIA
There are two aspects of using VR as a treatment that need to be explored: the science/pathophysiology of amblyopia and strabismus, and the more esoteric philosophical/psychological factors associated with the treatment approach.
Pathophysiology of Amblyopia and Strabismus
First let us consider the neurology of the visual system. Binocular neurons are present in the visual cortex of primates within the first week of life.3 It is argued that the stereopsis comes about from a functional change (i.e. a change in signal strength) as opposed to a structural or physical change.1,3 This theory suggests that when we are treating a visual system, we are affecting change through functional or sensory impact, not structural (muscular) change.
We pursue stereopsis in order to increase our client’s visual outcomes, but it has the by-product of improving the visual system’s stability, thereby limiting further regression of acuity. Stereoacuity creates the most rich and full visual experience for our clients. Research suggests that it leads to better self-awareness, visual motor skills and confidence.1,4
The premise of amblyopic or strabismus treatment is to reduce the suppression of the offending image in the cortex. But once this suppression is reduced, then the brain is left with two disparate images. It is critical to strengthen cortical fusion at the same time as the suppression reduction. That is the purpose behind the use of monocular fixation in binocular field (MFBF) activities. Such treatment is usually conducted with the use of mirrors and polarised or red-green activities. The limitations of these activities often lead to a halt in progress. The introduction of VR systems makes it possible to alter the blur in front of the ‘good eye’ or alter the luminance and contrast between the eyes. This flexibility means each activity can be custom designed to meet the client’s visual system at a level where they can experience small amounts of success. Over ensuing sessions, the blur or contrast can be reduced while maintaining fusion.
Philosophy/Psychology of VR
The Phenomenon of VR
The phenomenon of virtual reality calls for deeper inquiry, especially within the constructs of ‘presence’ and ‘attention’. Presence is a subjective phenomenon. When you are immersed in the virtual reality world, many of your perceptual aspects are altered, and to some degree, your perception overlooks knowledge – everything is perceived as if the technology was not involved in the experience. We rely on, and assert our perceptions as being absolute, and yet dismiss them when the experience warrants it.
One of the most challenging aspects of any therapy program has always been compliance. From an anecdotal perspective, our practice across three branches does not have episodes of missed VR appointments, which is not the case with our traditional in-office treatment. VR clients are required to come to our practice twice per week for six weeks. With VR, children are incredibly motivated, and parents can better appreciate the value in what we are offering. And of course, increased compliance results in increased outcomes.
While VR seems to be at the forefront of what we should be offering our clients, what does the evidence say? Although it is early days and the number of studies are still very small, the evidence is positive. A study from 2017 found that before treatment, 47.1% of participants had unmeasurable stereoacuity, and after treatment only 11.8% had unmeasurable acuity.4 Certainly, our own practice data, while limited, yields similar evidence.
The most interesting discovery from our experience has been that the use of the VR equipment in our office alone did not transfer to clinical improvements. While clients were reporting amazing changes in their experience, we were not able to record these changes during examination in the consulting room. Frustratingly, after six weeks and around 12 sessions, their acuity, refraction, turn and suppression all remained very much unchanged.
As a result of this, we initiated a change to our protocol. Clients were given two or three activities to continue to work on at home between their in-office sessions.
These included more traditional work we were otherwise doing, such as monocular fixation in a binocular field activities, accommodative work, monocular skills and eye movements. After the protocol change, we began to measure improvements in stereoacuity and visual acuity. Reinforcement with home vision therapy is what appears to yield the most improvement to outcomes. Changes in function require repetition and time. It seems that anything worth doing is worth doing well.
If you are considering implementing a VR program in your practice, you need to take into consideration the amount of room required. A standard consulting room can be a little limiting since free movement is required. There is some need for IT skills, and having reliable internet with WIFI connections is important. To avoid frustration with the technology, we advise being organised to ensure updates are uploaded ahead of time, and not at the precise moment your patient enters the room.
A word of warning: We are still unsure as to how many sessions are required to create a stable stereoscopic system. Some clients report regression between their six-week units. Another aspect is that of age limits. Younger children may not have the speech and language skills to articulate their experience, and yet, we have measured three to four lines of acuity improvement in children as young as seven, after only six sessions.
In summary, VR systems offer exceptional quality of dichoptic viewing, which is critical for development of stereoacuity. They offer an immersive environment that has a phenomenal effect on attention and presence. The enjoyment and novelty for clients mean that we can train amblyopia and strabismus effectively. But, VR is not a ‘point and shoot’ system and home vision therapy will be critical to improving the outcomes.
Sarah Sweeney B App Sc (OPTOM) FACBO graduated from Queensland University of Technology in 2000 and is a director at RA Optometrists in North Brisbane.
Ms Sweeney has been a guest lecturer and a clinical advisor to optometry students and has spoken at optometry conferences. In 2008, she received a Fellowship from the Australasian College of Behavioural Optometrists (ACBO) and she was Chair of the ACBO fellowship examination board from 2013–2016.
- Fortenbacher, D. Bartolini A. Dornbos B. Tran T. Vision Therapy and Virtual Reality Applications. Adv Ophthl Optom. 2018. 3: 39-59
- www.medicaldirector.com/resources/patientengagement- survey-2018
- Beilin, H. Mechanisms in the Explanation of Developmental Change. Advances in Child Development and Behavior, 1994
- Ziak, P. Holm A. Halicka J. Mojzis P, Pinero D. Amblyopia Treatment of Adults with Dichoptic Training Using the Virtual Reality Oculus Rift Head Mounted Display: Preliminary Results. BMC Ophthalmology. 2017. 17: 105