A Reminder That the Retina is an Extension of the Brain
By Kapil G. Kapoor, MD
In a world where Amazon is planning delivery by drone and driverless cars are being tested for market, it often surprises me when certain aspects of medicine remain chronically unchanged, often archaically so. To some extent, our diagnostic approach to Alzheimer’s disease and other dementias remains this way, as the gold standard for diagnosis is still neuropathology. To spell this out explicitly, this of course means definitive diagnosis is by brain biopsy at autopsy after a patient expires, and there are no great biomarkers for accurate diagnosis otherwise. That approach gives me pause and certainly feels under-evolved and obsolete, but it is actually modern medicine. Robin Williams is perhaps the most salient representation of this, as there was widespread media surprise when the fan-favorite comedian was only known to have Lewy body dementia after he was diagnosed by autopsy after his passing.
At the very least, this underscores the critical need for noninvasive biomarkers to identify neuropathologies ante mortem. With this background in mind, it is very gratifying to share some of the novel research that may be adding important components to our diagnostic approach to dementias, specifically Alzheimer’s disease, which is the topic of this month’s medical update.
We are learning that the retina may serve as a diagnostic tool for Alzheimer’s disease. This makes perfect sense, as we have long understood the retina as being an extension of the brain, with a key difference being that we can visualize the retina directly, noninvasively and cost-effectively.
So, let’s dig into the research!a
Optical coherence tomography (OCT) is a noninvasive imaging technique that creates high-resolution images of all nine layers of the neurosensory retina, as well as the vascularized choroid that lies underneath it. OCT images are demonstrating (within a couple of seconds!) that Alzheimer’s disease is associated with thinning of the retinal nerve fiber and retinal ganglion cell layers. Further research is also suggesting that the degree of thinning is correlating with disease severity, as measured by standardized measures of global cognition. This adds not only diagnostic information, but also a way to prognosticate disease progression and an objective method to assess therapeutic intervention.
Fluorescence imaging of the retina with curcumin as a plaque-labeling fluorochrome has also been utilized to identify retinal amyloid-beta in humans. This is another noninvasive method of retinal imaging that is showing significant promise in Alzheimer’s diagnosis.
A couple of seconds to diagnosis is even faster than Amazon Prime – even if aided by drone! If we can diagnose neurodegenerative conditions earlier in the disease process, therapeutic intervention may have a better chance of changing the course of the disease. Certainly, more research is needed to elucidate precisely what role retinal imaging can play in the diagnostic approach to Alzheimer’s disease and other dementias. These findings highlight the often-recurring theme of the eyes being the gateway to one’s health, quickly giving a detailed snapshot of one’s overall wellbeing. To learn more about our research efforts or how you can participate, please contact our research department!
References:
1.Shariflou S, Georgevsky D, Mansour H, Rezaeian M, Hosseini N, et al. Diagnostic and Prognostic Potential of Retinal Biomarkers in Early Onset Alzheimer’s Disease. Curr Alzheimer Res.2017;14(9):1000-1007.
2. Lad EM, Mukherjee D, Stinnett SS, Cousins SW, Potter GG, et al. Evaluation of inner retinal layers as biomarkers in mild cognitive impairment to moderate Alzheimer’s disease. PLoS One. 2018 Feb 8;13(2):e0192646.
Kapil G. Kapoor, MD is a Board certified ophthalmologist specializing in vitreoretinal surgery. wagnerretina.com
