People who have a specific type of glaucoma, called normal-tension glaucoma, have a higher risk of developing Alzheimer’s disease, according to a large, nationwide study from Taiwan that will be presented at this year’s 126th annual meeting of the American Academy of Ophthalmology.
Glaucoma is a group of eye diseases that can lead to vision loss and blindness caused by damage to a nerve in the back of the eye, known as the optic nerve. Normal-tension glaucoma (also known as low-tension glaucoma) is a condition where the optic nerve is also damaged, but eye pressure stays within a normal range (between 12 to 21 mm Hg).
“The findings from our study have both clinical and public health implications,” Yu-Yen Chen, MD, PhD, lead researcher and ophthalmologist at Taichung Veterans General Hospital, told Seasons. “Clinically, when treating patients with NTG, ophthalmologists need to focus not only on the medial aspects of NTG but also on changes in cognitive function or memory.”
Chen added that patients with NTG who are at a higher risk for AD – including older patients, female patients and patients with stroke – should be referred to a neurologist or psychiatrist if early signs of AD become apparent.
Furthermore, she said “policy makers are encouraged to enforce screening for AD risk in patients with NTG and to provide more substantial and integrated care.”
Chen and her colleagues analyzed data collected over 12 years from Taiwan’s National Health Insurance Research Database and compared the incidence of Alzheimer’s in 15,317 patients with NTG and 61,268 patients without glaucoma.
They found that people with NTG were 52% more likely to develop Alzheimer’s, and patients who were older, female or had a history of stroke had the highest incidence. Furthermore, the team found that certain treatments – like the use of eye drops – did not protect against Alzheimer’s or increase the incidence of the disease in patients.
Even though not everyone with glaucoma will develop AD, Chen said the findings from the study reveal how they may be related and why early screening and other preventive measures should be taken.
“Glaucoma is a multifactorial disease. Early diagnosis is the most important,” she said. “Policymakers are also encouraged to enforce screening for AD risk in patients with NTG and to provide a referral to neurologists.”
Connection between normal-tension glaucoma and Alzheimer’s
Rohit Adyanthaya, MD, a board-certified ophthalmologist, said patients with NTG may be at a higher risk of AD because they experience slow damage to the optic nerve.
“The optic nerve is connected to the brain and part of the same nerve tissue, and since the optic nerve slowly degenerates, the same mechanism probably causes degenerative changes in the brain tissue leading to Alzheimer’s disease,” he said.
Chen added that both diseases are chronic, progressive neurodegenerative diseases with an age-related and female-predominant incidence. In structural and pathological studies, for example, patients with AD exhibit retinal ganglion cell loss and retinal nerve fiber layer thinning—similar to patients with NTG.
“Glaucoma and AD share similar pathophysiological and underlying mechanisms,” Chen said, which could be potential reasons why patients with NTG are at higher risk of developing AD.
However, other experts say more research is needed to better understand the association.
“Further work is necessary to confirm if the relationship is co-incidental or if other confounding variables might account for the association,” said Andrew Lee, MD, clinical spokesperson for the American Academy of Ophthalmology and neuro-ophthalmologist at Houston Methodist.
Lee said from a neuro-ophthalmic standpoint, “we would not advocate for any additional screening or change in evaluation for NTG in regards to AD.”
Symptoms of glaucoma
Many people with glaucoma may not have any noticeable symptoms or signs in the earlier stages, which can make it easy to miss. However, some symptoms may occur suddenly. These include:
- Eye pain or pressure
- Red eyes
- Low vision or blurred vision
- Seeing rainbow-colored halos around lights
- Nausea and vomiting
What to do if a loved one is showing symptoms or already has a diagnosis of glaucoma
The first step, Adyanthaya said, is to should speak with a specialist to discuss your options.
“There are many treatments for glaucoma, including eye drops, lasers and surgery, which will definitely prevent or at least decrease vision loss from glaucoma,” he said. “However, these treatments are unlikely to decrease the incidence of Alzheimer’s disease.”
Daniel Laroche, MD, a glaucoma specialist in New York and a clinical assistant professor of ophthalmology at Mount Sinai Medical Center, told Seasons he recommends patients over 50 with traditional high-pressure glaucoma to consider certain surgical procedures to lower any pressure in the eye.
“Early cataract surgery and microinvasive glaucoma surgery works the best to lower intraocular pressure, reduce medication burden and preserve visual field,” he said. “Lowering eye pressure is currently the best treatment we have for glaucoma.”
Other ways to prevent glaucoma and other forms of eye diseases
Experts say there are a few things you can do to help an older adult prevent and detect glaucoma during its early stages:
- Get regular eye exams – Laroche said people 60 and older should have their eyes checked every year or two to check for cataracts, glaucoma, macular degeneration and retinopathy. There are other recommendations based on your age.
- Know your family’s eye health history and your risk factors – People with a family history of glaucoma, as well as African Americans over 40 and Hispanics over 60 have an increased risk of developing glaucoma. Adyanthaya said other risk factors can include medications that increase pressure in the eyes, chronic eye inflammation, myopia and diabetes.
- Wear eye protection – Wearing eye protection like sunglasses or goggles can protect your eyes from the sun, during sports or when working with chemicals or power tools.
Caregivers and older adults who have questions about other preventive measures, including the use of eye drops or other treatments, should consult with their health care provider.