Alzheimer’s impacts the brain but may also affect the eyes. A recent study found that almost 94% of participants with an unusual vision problem also exhibited Alzheimer’s pathology. Researchers emphasized the need for further clinical understanding of posterior cortical atrophy (PCA) to aid in the early detection of Alzheimer’s.
Alzheimer’s is well recognized to affect brain skills such as memory, spatial awareness, speaking, and writing, but what is not much known are the changes to the brain that may also affect the eyes [1].
Previous research indicates that alterations in the brain associated with Alzheimer’s may also transpire in the retina [2]. Additionally, researchers have observed abnormalities in the eyes with Alzheimer’s, such as loss of visual field, color vision, and contrast sensitivity needed for reading [3,4].
In a recent study published in The Lancet Neurology, scientists from the University of California, San Francisco, investigated the impact of a rare eye disorder called posterior cortical atrophy (PCA), often known as Benson’s syndrome, to see how Alzheimer’s affects the eyes [5]. According to this study, some people—women in particular—may have impairments in their visual perception even when their cognitive abilities appear normal.
The Recent Research Findings
Researchers looked at data from nearly 1,100 patients with posterior cortical atrophy (PCA), a disorder characterized by shrinkage of brain tissue in areas of the brain involved in processing and responding to visual information. In daily life, this can result in issues with reading comprehension or driving depth perception, particularly at night.
Autopsy results revealed that 94 percent of these patients displayed symptoms consistent with Alzheimer’s, indicating that it virtually always causes PCA.
According to the National Institutes of Health, PCA is typically diagnosed at age 59, which is five or six years earlier than the average diagnosis of Alzheimer’s. Women are more likely to get it than men; they make up 60% of cases [6].
The study discovered that although the majority of PCA patients may initially exhibit normal cognitive function, it might take up to four years for them to receive a diagnosis. By then, they frequently suffer from mild to moderate dementia, which includes impairments in speech, behavior, memory, and executive function.
However, according to principal study author Marianne Chapleau, PhD, a neuropsychologist and postdoctoral fellow in neurology at the University of California, San Francisco, many people may be unaware that they have PCA or that it can be an early Alzheimer’s sign.
Dr. Chapleau states that because people tend to link visual problems to aging vision rather than dementia, visual symptoms in PCA may manifest before more prominent and widespread cognitive deficits linked with Alzheimer’s disease. Consequently, they miss out on the chance for earlier intervention.
Visual Perception Issues
At the time of their PCA diagnosis, 61% of research participants experienced what is known as “constructional dyspraxia,” or the inability to duplicate basic designs or figures. Furthermore, about half of them struggled to identify the locations of things they observed and to perceive more than one object at a time.
According to Andrew Budson, MD, chief of cognitive behavioral neurology at VA Boston, a neurology professor at Boston University (who was not involved in the study), it makes sense that when someone exhibits these symptoms, they might not think of Alzheimer’s. They typically visit their optometrist first to have the prescription for their glasses corrected; if the optometrist is unable to assist, they may then visit an ophthalmologist. Only at that point, the ophthalmologist might refer the patient to a neurologist, realizing that the issue is probably in the brain rather than the eyes.
However, a PCA diagnosis may not even result from that initial neurology session. Individuals may still require an MRI that reveals brain shrinkage patterns that are consistent with PCA, as well as a visit with a dementia or memory disease specialist.
Advantages of an Early Diagnosis
Budson emphasized the importance of receiving a PCA diagnosis as soon as possible because there are strategies people can take to manage their symptoms. Since Alzheimer’s disease is often the cause of PCA, treatment with anti-amyloid medications, such as lecanemab (Leqembi), may reduce the symptoms.
While more research is needed, it may be feasible to diagnose PCA in its earliest stages and prevent it from worsening with these Alzheimer’s treatments.
Although there is no known cure for PCA, lifestyle modifications can still have a positive impact.
According to Dr. Chapleau, maintaining a healthy lifestyle, including cognitive activities, a balanced diet, and regular exercise, may improve overall brain health. After a diagnosis, therapies such as cognitive therapies, medication, and customized care plans can help manage symptoms and decrease the progression of dementia.
References
- Hussain, A., Sheikh, Z. and Subramanian, M., 2023. The Eye as a Diagnostic Tool for Alzheimer’s Disease. Life, 13(3), p.726.
- Koronyo, Y., Rentsendorj, A., Mirzaei, N., Regis, G.C., Sheyn, J., Shi, H., Barron, E., Cook-Wiens, G., Rodriguez, A.R., Medeiros, R. and Paulo, J.A., 2023. Retinal pathological features and proteome signatures of Alzheimer’s disease. Acta Neuropathologica, 145(4), pp.409-438.
- Romaus-Sanjurjo, D., Regueiro, U., López-López, M., Vázquez-Vázquez, L., Ouro, A., Lema, I. and Sobrino, T., 2022. Alzheimer’s disease seen through the eye: ocular alterations and neurodegeneration. International Journal of Molecular Sciences, 23(5), p.2486.
- Kim, H.J., Ryou, J.H., Choi, K.T., Kim, S.M., Kim, J.T. and Han, D.H., 2022. Deficits in color detection in patients with Alzheimer disease. Plos one, 17(1), p.e0262226.
- Chapleau, M., La Joie, R., Yong, K., Agosta, F., Allen, I.E., Apostolova, L., Best, J., Boon, B.D., Crutch, S., Filippi, M. and Fumagalli, G.G., 2024. Demographic, clinical, biomarker, and neuropathological correlates of posterior cortical atrophy: an international cohort study and individual participant data meta-analysis. The Lancet Neurology, 23(2), pp.168-177.
- What Are the Signs of Alzheimer’s Disease? National Institute on Aging. https://www.nia.nih.gov/health/alzheimers-symptoms-and-diagnosis/what-are-signs-alzheimers-disease. Accessed: 2nd February, 2024.
- Pelc, C. Alzheimer’s may begin with unusual vision problems, study finds. Medical News Daily. https://www.medicalnewstoday.com/articles/rare-eye-condition-linked-to-alzheimers. Published Online: 25th January, 2024.
- Rapaport, L. Visual Perception Problems May Be an Early Alzheimer’s Sign, Especially in Women. Everyday Health, https://www.everydayhealth.com/alzheimers-disease/visual-perception-problems-may-be-an-early-alzheimers-sign-especially-in-women/. Published Online: 24th January, 2024. Accessed: 2nd February, 2024.