What the future holds
Dr Laura Edwards and Dr Lindsay Rountree discuss their take on research into visual field
Dr Laura Edwards
05 March 2020
Testing a person’s visual field has come a long way since it was first described by Hippocrates in 5BC. However, since the invention of the Goldmann perimeter in 1945, not a great deal has changed in the way we actually test our patient’s visual field.
Working in a busy glaucoma clinic means I am forever gazing at visual field plots. However, as any practitioner and technician will know, sometimes patients just aren’t very good at doing them. In fact, many patients attending glaucoma clinics dislike the test, even though they appreciate the importance of doing it. Current tests require prolonged concentration which can be difficult, especially for our older patients, who, incidentally, are at a higher risk of glaucoma progression. This can leave us wondering if a patient’s vision has actually got worse or were they just feeling a bit tired on that particular day? Furthermore, we are faced with the challenge of improving the sensitivity of the tests. Even with modern automated analysers, defects caused by glaucoma may not be evident until a lot of damage has happened.
Currently, there are many patient-centred avenues of research being explored. Specifically, the use of tracking eye movements to aid disease detection is an exciting prospect. It is already well documented that patients with eye disease make different types of eye movements when compared to those with healthy vision. This is evident when performing a variety of different tasks, such as recognising faces or watching TV. A person’s eye movements can be recorded using inexpensive and readily available equipment called an eye tracker. They can be fitted to a laptop or screen so that natural eye movements can be observed while the individual is simply watching TV or looking at pictures.
This is a more comfortable and natural way to observe someone’s vision, compared to the tests we use in clinics. It is also a cheap, portable option which could be employed for screening purposes in less economically developed countries. There are certainly promising advances in this area of research so far. However, it is not without its challenges. Further developments are required before eye movements can provide a clinically useful way of detecting disease. Ultimately, the future of visual field testing should ensure that the tests will become easier for patients, more reliable, more affordable, and more widespread.
Working in a busy glaucoma clinic means I am forever gazing at visual field plots. However, as any practitioner and technician will now, sometimes patients just aren’t very good at doing them
I was first drawn to researching the visual field as I know how valuable this information can be in practice, yet how challenging the test can be for both patient and practitioner alike. Many of the current techniques were established before glaucoma was well understood; indeed, our knowledge of glaucoma, and the techniques used in its investigation, are continually evolving.
An example of this evolution is ‘frequency-doubling’ perimetry, which was originally thought to preferentially stimulate the retinal ganglion cells first lost in glaucoma, leading to an earlier diagnosis. As we now suspect that all types of ganglion cell are targeted equally in glaucoma, our explanation of the test to patients should differ accordingly. We know that visual field ‘defects’ may occur due to small pupils or cataract. These can be difficult to distinguish from true glaucomatous defects, and may result in unnecessary referrals, so we should select a different type of visual field test for such patients or interpret findings cautiously.
Current research groups are approaching the problem of visual field testing in different ways, and the following ideas could be incorporated into clinical practice in the near future. Some groups are investigating the use of other stimuli, as the traditionally used white circular spot of a set size is somewhat arbitrary. For example, different sized stimuli presented in different areas of the visual field (smaller stimuli in the centre, and larger stimuli further into the periphery), or changing the size of the stimulus as part of the test, either instead of, or in addition to, changing the brightness of the stimulus.
Some research groups are attempting to make the visual field test more accessible to patients. The use of a computer screen, or virtual reality headsets may be more comfortable than the bowl design, as well as being more portable. Tests which incorporate ‘preferential looking,’ whereby the patient simply looks in the direction of a perceived stimulus rather than pressing a button, may make it easier to assess young children, or those who struggle with the current design. Some of these ideas are still in their infancy, and it may take time before we see them adopted to clinical practice.
Also in this series
- In the field Optical assistant, Lisa Skelton, discusses carrying out visual field tests
- A perfect match How artificial intelligence is being applied to visual fields
- The visual pathway Dr Samantha Strong shares a journey through the visual pathway
- Understanding the test types Dr Lindsay Rountree introduces the most frequently used visual field tests in routine practice
- The patient and the visual field test Dr Lindsay Rountree discusses making the patient’s experience of visual field testing a positive one
- Visual fields: the jargon OT explores the terms commonly used on a visual field plot