Hearing and the Retina: A (Not-So) Surprising Link

Retinal Vasculature: A Biomarker for Hearing Acuity?

A recent retrospective study, published in Scientific Reports, explores the retinal vasculature as a potential noninvasive biomarker for the early detection of hearing loss. Researchers employed a newer retinal metric called fractal dimension (FD)—a measure of vascular branching complexity and density obtained via fundus photography. Lower FD values suggest sparser vascular networks, potentially indicating microvascular dysfunction.

After analyzing data from 575 patients at the Shanghai Health and Medical Center who underwent both ophthalmic and audiologic assessments, the study found that greater retinal fluid flow (ie, retinal FD) corresponded with better hearing sensitivity. Specifically, a 1 standard deviation increase in arteriolar FD was associated with a 2.85 dB decrease in hearing threshold at 1 kHz. In comparison, a similar rise in venular FD was associated with a 2.61 dB reduction at 2 kHz. In other words, participants with denser retinal vasculature showed sharper hearing acuity.

The authors propose that the retina and cochlea, both being highly vascular and sensitive to ischemia, may undergo parallel microvascular changes. Shared vascular pathology could affect cochlear blood flow, impair sensory hair cells, and ultimately lead to hearing loss. They reference Susac syndrome—an occlusive microvascular disease affecting the brain, retina, and inner ear—as a precedent for interconnected vascular damage.

Additionally, two mechanistic hypotheses were proposed: First, impaired neurovascular coupling due to pericyte dysfunction may reduce oxygen delivery in both retinal and cochlear tissues. Second, a compromised glymphatic-like clearance system in the cochlea could lead to toxin buildup and damage, mirroring similar clearance deficits linked to lower retinal FD.

Overall, the authors conclude that retinal FD offers a promising noninvasive biomarker for early detection of hearing loss, with potential for informing preventive strategies.

My Two Cents

Of all the interesting quotes from the paper, I found the hypothesis that the retina and the cochlea undergo parallel microvascular changes to be absolutely mind-blowing. It makes total sense, as both are highly vascular and sensitive to ischemic changes. Taking this a bit further, the fact that the study found patients with denser (likely healthier) retinal vasculature had superior hearing acuity also supports the hypothesis that a healthy retina could also indicate better hearing. Although it’s concerning that everyone has headphones and earbuds in their ears now, it does make me wonder if this will lead to reduced hearing.

OUTSIDE THE LANE

Ocean Confers Superior Health Benefits, Study Finds

A nationwide study reveals that people living near the ocean may enjoy longer lives—sometimes a year or more above the US average life expectancy of 79 years of age—while those situated near extensive inland waterways in urban areas may fare worse, often dying slightly younger, at around 78 years of age.

Examining more than 66,000 US census tracts and categorizing them based on proximity to coastal versus inland “blue spaces,” researchers found a distinct benefit for coastal residents. That advantage is likely due to a combination of environmental and social advantages: milder temperatures, fewer scorching hot days, cleaner air, more recreation options, better transportation infrastructure, lower drought vulnerability, and higher incomes.

By contrast, urban dwellers living near inland rivers or lakes may contend with greater pollution, poverty, and flooding risks, as well as fewer safe spaces for physical activity—factors that could negate any health benefits typically associated with “blue spaces.” The findings challenge the notion that all water-adjacent living environments confer equal health benefits, instead highlighting the superior effect of coastal environments on longevity. Lead researcher Jianyong “Jamie” Wu and postdoctoral researcher Yanni Cao emphasized that the study is the first systematic examination of how different types of water-rich environments affect life expectancy nationwide. Cao additionally noted that such environmental and social determinants of health may help explain why US life expectancy trends have declined more sharply—and rebounded more slowly—than in other wealthy countries.

My Two Cents

Okay, I’m not sure how to take this. On one hand, it makes perfect sense that those who live in coastal areas are likely healthier and have better opportunities to maintain their health. Down here in the Gulf South, many regions with beachfront access are also the most expensive, likely meaning those who are more affluent live in those areas. I would also argue that those individuals are more likely to afford healthier food.

Living just a few miles away from the Mississippi River, it also makes sense that those who live near waterways such as this would be at a higher risk of health issues, as the area where I reside is actually nicknamed the “Cancer Corridor” due to the large number of chemical plants that line the Mississippi nearby. Personally, I would be interested in seeing what the data says about the Great Lakes of Michigan, as those small communities that dot the “fresh coast” are some of the healthiest and most well-rounded I’ve ever seen.

CAN YOU RELATE

This week’s newsletter is a bittersweet one for me, personally, as it’s the final newsletter for my editor, Karen Roman. Karen is one of those people who you are forever grateful that God put in your life. There is no one more understanding, compassionate, or caring than she is in the field. From adopting troubled dogs to lending a helping hand to drum up some ideas for an article in Modern Optometry, she was always there.

I’ll never forget when she and her team approached me at ModLive a few years back and mentioned that they would like me to write a newsletter. I remember looking at them, stunned and honestly quite confused. I immediately asked, “Why in the world would anyone want to know what I’m thinking???” They assured me that being an extremely high-volume optometrist who practiced in one of the county’s preeminent practices would draw readers in. Karen never put any guardrails on my writing and only had to correct a few of the especially dumb things that I had written, which undoubtedly resulted in far fewer angry emails (the key word choice there being fewer). I still get quite a few, though, because she always lets me call out the hypocrisy that I see within the field.

Thank you, Karen, for everything. Good luck with your future; I have zero doubts that you’ll flourish, and your gain will be the eye care field’s significant loss. For now, goodbye; for tomorrow, good luck; and for forever, my eternal thanks!