New research from the New York Eye and Ear Infirmary of Mount Sinai shows that people with a certain type of age-related macular degeneration (AMD), which is the leading cause of blindness in the US, are at a high risk for heart disease and stroke.

The first study to show a connection between the diseases was published in the July issue of Retina.

Researchers have hypothesized a link between AMD and cardiovascular disease for the past three decades, but until now there hasn’t been any concrete evidence to support this. 

“Our retinal team answered this important question,” says lead author R. Theodore Smith, “by focusing on two different varieties of AMD that can be seen with advanced retinal imaging.”

And they found “that only one form of AMD, that with subretinal drusenoid deposits, is tightly connected to high-risk vascular diseases, and the other form, known as drusen, is not.”

“If ophthalmologists diagnose or treat someone with the specific subretinal drusenoid deposits form of AMD, but who otherwise seems well,” the researcher highlights, “that patient may have significant undetected heart disease, or possibly carotid artery stenosis that could result in a stroke. We foresee that in the future, as an improved standard of care, such patients will be considered for early referral to a cardiologist for evaluation and possibly treatment.”

Damage to the macula, the center region of the retina that is crucial for reading and driving vision, makes AMD the most common cause of vision loss and blindness in adults over 65.

Drusen is a common type of early AMD in which a layer beneath the retina develops tiny, yellow cholesterol deposits.

They may rob the retina of blood and oxygen, which could result in blindness. The production of drusen can be slowed down with the right vitamin intake.

Subretinal drusenoid deposits (SDD), a less well-known primary form of early AMD, are difficult to identify without sophisticated retinal imaging.

These deposits, which are similarly formed of fatty lipids and other substances, develop in a layer beneath the retina’s light-sensitive cells, where they are also linked to vision loss. At the moment, there is no known way to treat SDD.

Using optical coherence tomography (OCT), a cutting-edge imaging technique that produces high-resolution cross-sectional scans of the retina, Mount Sinai researchers examined 126 patients with AMD. Patients also filled out health history questionnaires that asked about things like heart disease and stroke.

Among the study participants, 62 had SDD and 64 had drusen; 51 of the 126 patients overall (or 40%) disclosed having cardiovascular disease or a history of stroke, and the majority (66%) of those individuals had SDD. Comparatively few (19%) of the 75 individuals without a history of heart disease or stroke had SDD.

According to statistics, SDD was three times more likely to occur in patients with cardiovascular illness or stroke than in those without.

The researchers hypothesized that the underlying cardiac and vascular disease probably impairs blood flow in the eye, resulting in SDDs beneath the retina and eventually causing vision loss and blindness.

They “believe poor ocular circulation that causes SDDs is a manifestation of underlying vascular disease,” adds author Jagat Narula. 

This has important effects on public health and can make it easier to screen the population and find diseases.

According to authors, such patients should be encouraged to see a cardiologist if they are observed at an eye clinic. SDDs, on the other hand, may become a risk factor for underlying vascular disease in asymptomatic individuals in general care or a cardiology clinic if clinically supported in prospective investigations. In the prospective studies that are currently being done, it will also be important to find out how SDDs and macrovascular diseases relate to each other in terms of time.

Blood samples were also gathered from patients, and analysis suggests that genetic risk factors, in addition to vascular reasons, may play a role in SDD cases. In particular, they discovered that in certain cases, the ARMS2 gene caused SDD without the involvement of vascular disease.

According to Richard B. Rosen, MD, Chief of the Retina Service for the Mount Sinai Health System, “this study further demonstrates that AMD is not a single condition or an isolated disease, but is often a signal of systemic malfunction which could benefit from targeted medical evaluation in addition to localized eye care.”

It advances our understanding of this terrible condition, which deprives so many people of the enjoyment of good vision in their senior years, he concludes.

Image Credit: Getty

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