A nice article in the Tuesday Science Times section of the New York Times by Jane Brody titled “How Vision Loss Can Affect the Brain” deservedly made the rounds of the VT-OD list the other day. It is subtitled: A growing body of evidence suggests that when older people’s brains have to work harder to see, declines in language, memory, attention and more could follow, and begins with this important holistic observation: “Medical practice tends to divide its clients — you and me — into specialties defined by body parts: ophthalmology, neurology, gastroenterology, psychiatry and the like. But in fact, the human body doesn’t function in silos. Rather, it works as an integrated whole, and what goes awry in one part of the body can affect several others.”
The article seems to have gained traction around the world, being picked up by a variety of news feeds including the Independent in the UK.
As its primary reference, the article cites a study published in July in JAMA Ophthalmology, Association of Vision Impairment With Cognitive Decline Across Multiple Domains in Older Adults. The research is based on data from the Baltimore Longitudinal Study of Aging during the period of 2003 to 2019, with vision and cognitive measures obtained from participants ranging from 60 to 94 years of age. The authors suggest that the association between vision and cognition differs between visual acuity, contrast sensitivity, and stereo acuity and that patterns of cognitive decline may differ by type of vision impairment, with impaired contrast sensitivity being associated with declines across more cognitive domains than other measures of visual functioning.
There is an invited commentary on this study in the same issue of JAMA Ophthalmology, as part of JAMA Network Open, titled “Beyond Visual Acuity—A Comprehensive Assessment of Vision and Cognition in Older Adults With Visual Impairment“. These authors provide a useful term, the Visual Function System (VFS), with visual acuity as merely one, albeit the most commonly cited visual measure. They indicate that although the study on Visual Impairment and Cognitive Decline (cited by Ms. Brody) is of great interest, it should be noted that other VFS components, such as visual field and color vision, were not included, which may limit the study’s main conclusion that impaired contrast sensitivity is associated with declines across several cognitive domains. They write: “Future studies investigating the association between the spectrum of VFS components and cognitive domains are needed to confirm the study’s findings. Critically, the cumulative impact of the deterioration in multiple aspects of the VFS needs further work. This information may provide important evidence to support a more comprehensive clinical assessment of the VFS as part of a public health strategy for early detection and management of cognitive decline in older adults with VI.”
As the authors of the JAMA Ophthalmology article concede, the concepts here are not particularly new. Of course Harry Wachs has long championed the role of cognition and visual-spatial thinking as essential to the spectrum of functions in the VFS. On a personal note it brought back memories of a presentation I did (so long ago that I used a slide projector) to demonstrate the application of visual perceptual testing for patients having visual impairment. It was at an annual meeting of the American Academy of Optometry in the late ’70s (1970s, that is) or early ’80s based on collaborative clinical work between the Feinbloom Center and the Pediatric Unit of The Eye Institute at the Pennsylvania College of Optometry with which I was involved. My premise was that before training low vision patients on the use of various optical and non-optical aids, it would be helpful to evaluate their visual processing abilities, particularly in visual discrimination and in visual sequential memory. This was subsequently explored by Lea Hyvärinen in an article on Visual Perception in Low Vision, in which she writes: “Abnormal visual information leads to changes in visual perception, and brain-damage-related visual impairment may alter or prevent one or several cognitive visual functions.”
More recently, Geoff Shayler explored many aspects of the VFS, particularly as they relate to ageing, in a four-part series in the UK journal Optometry Today in 2011. He subsequently wrote a nice synopsis of this which broadened the model to patients of all ages in his Optometry and Visual Performance article in 2015 titled The Use of Models to Help Our Understanding of Vision. What is new and exciting is the extent to which much of what Optometry has clinically pioneered is now being researched.