Alzheimer’s disease (AD) is the most common subtype of dementia. It is characterized by the accumulation of misfolded amyloidß (Aβ) and tau protein in the brain. Degenerative processes in the aging eye and brain show striking similarities.1,2
The retinal ganglion cell (RGC) and RPE layers have been identified as a major source of Aβ synthesis and secretion. Aβ is capable of eliciting local inflammation within the retinal tissue.1,3 (Aβ) deposits have been shown to be prevalent in the retinae of patients with AD. Clinical examples of shared ocular and brain pathology in AD patients include reduced thickness of the retinal nerve fiber layer (RNFL), abnormal retinal blood circulation, and reduced choroidal thickness.1-4
A recently published study of 3,877 randomly selected subjects suggests a significant link between three degenerative eye diseases—AMD, diabetic retinopathy (DR), and glaucoma—and AD.5 See Figure 1. Participants were age 65 and older and did not have AD at the time of enrollment. Over the five-year study, a committee of dementia experts diagnosed 792 cases of AD. Patients with AMD, DR, or glaucoma were at 40-50 percent greater risk of developing AD compared to similarly matched subjects without any of these eye conditions. Cataract diagnosis was not found to be an AD risk factor.
These and other recent investigative findings suggest common pathways between eye diseases and AD.4,5 Further studies to determine the potential of ophthalmic biomarkers of subclinical AD may identify people destined to develop AD. While it cannot be concluded from this study that people with AMD, DR, and/or glaucoma will get AD, optometrists and ophthalmologists should be aware of the risks of developing dementia for patients with these ocular diseases. Likewise, non-eye care clinicians that see patients with an ongoing history of these eye conditions should be diligent about ruling out dementia or memory loss.
Figure 1. Above left: diabetic retinopathy with center-involved edema. Above right: non-exudative AMD on fundus autofluorescence. Lower image: OCT ganglion cell + inner plexiform analysis.
Key Clinical Takeaways
Alzheimer’s disease (AD) is difficult to diagnose as well as treat.
Recent research has found a significant link between AD and three degenerative eye diseases: AMD, diabetic retinopathy, and glaucoma.
These findings support a hypothesis that cellular senescence, amyloid beta (Aβ), and inflammation have significant roles driving degenerative processes within they eye, as well as in the brain.
We can learn about the brain by examining and evaluating the eye and visual pathway.
Ratnayaka, J Arjuna et al. “Dementia of the eye: the role of amyloid beta in retinal degeneration.” Eye (2015).
Blasiak, Janusz et al. “Cellular Senescence in Age-Related Macular Degeneration: Can Autophagy and DNA Damage Response Play a Role?” Oxidative Medicine and Cellular Longevity 2017 (2017): 5293258. PMC. Web. 15 July 2018.
Parisi V, Restuccia R, Fattapposta F, Mina C, Bucci MG, Pierelli F. Morphological and functional retinal impairment in Alzheimer's disease patients. Clin Neurophysiol 2001; 112 (10): 1860–1867.
Ohno-Matsui K. Parallel findings in age-related macular degeneration and Alzheimer's disease. Prog Retin Eye Res 2011; 30(4): 217–238.
Lee, Cecilia S. et al. Ophthalmology-Based Ad Risk Factors: Glaucoma, Age-Related Macular Degeneration, And Diabetic Retinopathy Are Each Associated With Ad Risk In A Community-Based Cohort Study. Alzheimer's & Dementia: The Journal of the Alzheimer's Association, Volume 13, Issue 7, P1488 - P1489
Joseph J. Pizzimenti, OD, FAAO is a full-time faculty member of the Rosenberg School of Optometry at the University of the Incarnate Word in San Antonio, TX. Dr. Pizzimenti graduated from the Illinois College of Optometry and completed a residency in Rehabilitative Optometry and Ocular Disease at the University of Houston. He is a Fellow of both the American Academy of Optometry (AAO) and the Optometric Retina Society (ORS), serving as ORS President from 2012-2014. A long-time optometric educator, Dr. Pizzimenti is a frequent author and speaker on posterior segment disease.
Financial Disclosures: Dr. Pizzimenti has received honoraria and consulting fees from EyePromise, Zeiss, Genentech, Regeneron, Maculogix, and ThromboGenics.