Eyeworld

N OCTOBER 2020 | EYEWORLD | 29 by Maxine Lipner Contributing Writer gation showed that those with MCI or Alzhei- mer's disease had decreased blood vessel density in the macula. The eye affords a potentially unique diag- nostic opportunity for several neurodegenera- tive diseases. "You can directly, quickly, and in a non-invasive manner image the retina, which is an extension of the central nervous system, in high resolution using OCT and OCT angiogra- phy," Dr. Grewal said, adding that with ad- vances in such technology, there is interest that changes could be detected earlier and in greater detail and could also be used to monitor change over time. Sharon Fekrat, MD, a co-investigator with Dr. Grewal, said approximately 400 clinical trials looking at therapeutic medications for Alzheimer's disease have failed. This could be due to diagnostic challenges of Alzheimer's— either patients' disease state is too advanced for effective treatment or the diagnosis of Alzhei- mer's dementia is inaccurate and patients have another type of dementia. "Currently, the diag- nosis of Alzheimer's disease is incorrect about one-third of the time," she said. Early disease detection is not easy. Dr. Fekrat pointed out that in their recent study W hen it comes to Alzheimer's disease, several new studies share a common thread—they all involve the eye. One recent study involved macular degeneration and Alzheimer's, both of which are related to age and have abnormal extracellular deposits connected with neuronal degenera- tion, drusen, and plaques in common. 1 Another study indicated that there was an inverse con- nection between macular ganglion cell com- plex thickness and dementia. 2 A third studied a connection between amyloid plaques in the brain and aqueous humor, showing that in mice synthetic amyloid plaques injected into the cere- bral spinal fluid were immediately found in the aqueous humor. 3 A fourth study demonstrated that those with Alzheimer's had decreased reti- nal blood vessel density compared to those with mild cognitive impairment (MCI) or those with normal cognition. 4 Prompting this research is the huge unmet need for better Alzheimer's disease diagnosis, said Dilraj Grewal, MD, who recently investigat- ed a possible connection between Alzheimer's and retinal blood vessel density. 5 Their investi- Ocular connections to Alzheimer's disease About the doctors Sharon Fekrat, MD Professor of Ophthalmology Duke University School of Medicine Durham, North Carolina Dilraj Grewal, MD Associate Professor of Ophthalmology Duke University School of Medicine Durham, North Carolina References 1. Papadopoulos Z. Neovascular age-related macular degeneration and its association with Alzheimer's disease. Curr Aging Sci. 2020. Online ahead of print. 2. Fawzi AA, et al. Retinal imaging in Alzheimer's disease: In search of the holy grail. Ophthalmology. 2020;127:119–121. 3. Kwak DE, et al. Alterations of aqueous humor Aß levels in Aß-in- fused and transgenic mouse models of Alzheimer disease. PloS One. 2020;15:e0227618. 4. Yoon SP, et al. Retinal microvas- cular and neurodegenerative chang- es in Alzheimer's disease and mild cognitive impairment compared with control participants. Ophthal- mol Retina. 2019;3:489–499. 5. Yoon SP, et al. Correlation of OCTA and volumetric MRI in mild cognitive impairment and Alzheimer's disease. Ophthalmic Surg Lasers Imaging Retina. 2019;50:709–718. Relevant disclosures Fekrat: None Grewal: None continued on page 30

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