Glaucoma Detection Starts with an Eye Exam

A comprehensive eye exam does much more than update your prescription for glasses or contact lenses. Regular eye exams are also the best way to detect early signs of glaucoma, a group of diseases that develop when excessive pressure from fluid accumulating in the eye damages the optic nerve. If left untreated, glaucoma can cause vision loss and even blindness.

“The reason why glaucoma is scary is because there are no symptoms until the disease is most advanced,” says Vicente Diaz, MD, a Yale Medicine ophthalmologist and chief of ophthalmology at Bridgeport Hospital. “It progresses very gradually. First, you lose your far peripheral vision, and then slowly over time the vision loss moves toward the center of the eye. If you're not getting eye exams, it can be very difficult to know this is happening.”

While glaucoma is a leading cause of blindness in people over 60, half of the people who have the condition don’t realize it. A study published in JAMA Ophthalmology estimated that, in 2022, more than 4 million people in the United States were living with glaucoma. For about 1.5 million of those people, it was already affecting their vision—glaucoma can cause cloudy vision, night glare, and other symptoms eventually leading to loss of vision.

Glaucoma can’t be prevented or cured, but if it’s detected early, vision loss can be averted, often with prescription eye drops. If eye drops don’t work—or, as happens in some cases, lose effectiveness—there are minimally invasive glaucoma surgeries, including one that can be performed at the same time as cataract surgery, as well as laser treatments.

Dr. Diaz spoke with us about the key facts that patients need to know about glaucoma.

The optic nerve, which is found in each eye, contains more than a million nerve fibers that transmit visual messages to the brain. When you look at an object—whether it’s a paper clip, a boat, or a soccer ball—light passes through the eye’s lens to the retina, a light-sensitive layer lining the back of the eye. The retina converts that light into electrical signals that are sent through the optic nerve to the brain, which interprets them as visual images.

For a thorough eye exam, dilating drops are administered to make your eyes sensitive to light. This enables the doctor, using a special lamp, to identify changes to the optic nerve that can interfere with the visual information that’s sent to the brain.

Open-angle glaucoma, the most common type, disrupts this process when the naturally occurring fluid pressure in the eye, known as intraocular pressure (IOP), becomes excessive, potentially damaging the optic nerve. The IOP is measured in millimeters of mercury, or mmHg—a normal result is generally between 10 and 21 mmHg, while eye pressure above 21 mmHG is considered a risk factor and reason to monitor for glaucoma.

“Every eye is filled with fluid that nourishes and protects the eyes. Our eyes are making new fluid and draining the old fluid all the time,” Dr. Diaz says. Experts don’t always know how the process is disrupted to the point of causing excessive IOP, but they know that too much of it can damage the optic nerve. “If the drainage is not keeping up with fluid production, the eye gets too full,” he says.

It’s important to know that not every case of elevated eye pressure will lead to glaucoma. At the same time, not everyone who develops glaucoma has increased IOP. Glaucoma is diagnosed only if the optic nerve becomes damaged.

There are different types of glaucoma, including:

• Open-angle glaucoma: Fluid in the eyes normally drains via trabecular meshwork, a mesh-like tissue through which the fluid flows into the eye’s drainage system and ultimately into the bloodstream. A clogged drainage system can cause open-angle glaucoma. There are often no early symptoms, but the condition can gradually cause loss of peripheral vision, trouble seeing in low light, blind spots, and tunnel vision. If allowed to develop over a period of years, it can cause blindness.

• Closed-angle glaucoma: This is a less common type that develops when the iris, the colored part of the eye that surrounds the pupil, bulges, blocking fluid drainage. There are two kinds, and one of them, acute closed-angle glaucoma, is a medical emergency that warrants immediate attention because it can cause blindness in a matter of hours or days if it’s not treated. Initial symptoms come on suddenly, and include severe pain in one eye, blurred or hazy vision, and rainbow-colored circles around bright lights, which may be accompanied by nausea and vomiting. The second is chronic closed-angle glaucoma, which causes slow vision loss and may lead to blurry vision and headaches, among other symptoms.

There are many other, much less common types of glaucoma. Congenital glaucoma, for instance, is usually diagnosed when a baby is a few months old, and it’s often treated early with surgery. Secondary glaucoma may be caused by medicines such as prednisone or other corticosteroids, an injury, or a condition such as diabetes. In these cases, the underlying cause is addressed as part of the treatment.

If your ophthalmologist categorizes you as a “glaucoma suspect," it means you have one or more risk factors for glaucoma. Most glaucoma suspects never develop the condition. But you should monitor the situation by having regular eye exams and tests, Dr. Diaz says.

“If you are developing glaucoma, we want to catch it as soon as possible and start treatment as early as possible to prevent extensive, permanent vision loss,” Dr. Diaz says.

While anyone can develop glaucoma, risk factors include:

• Age over 60, especially in Hispanic or Latino people, or over 40 for Black people
• Family history, especially if a parent or sibling has glaucoma
• Conditions such as diabetes or high blood pressure
• Extreme nearsightedness (myopia) or extreme farsightedness (hyperopia)
• Certain medications, including corticosteroid medications such as prednisone

People who are considered glaucoma suspects should have a comprehensive dilated eye exam and other testing administered by an ophthalmologist every one to two years, Dr. Diaz says. “The testing revolves around looking at the structures in the eyes and the function of the optic nerve,” he adds.

During a comprehensive dilated eye exam, an ophthalmologist administers eye drops to dilate the pupils before using a slit lamp, a type of microscope with a bright light that allows the doctor to get a close look at the internal structures including the back of the eyes. This can identify potential signs of glaucoma, Dr. Diaz says. “There's a part of the nerve called the cup (a depression in the middle of the optic nerve),” he explains. “If the cup is very large, that increases your risk. If we see asymmetry in the cup—in one eye compared to the other—that’s suspicious as well.”

A variety of tests are available for monitoring glaucoma suspects, including three especially common ones. “Air puff tonometry” sends a brief puff of air into the eye—pressure is measured by the time it takes for the air to flatten the cornea, the eye’s outermost layer. A visual field test assesses your peripheral vision as you stare into a machine and press a button each time you see a small light appear in a different area. Optic nerve photography helps track changes over the course of years.

Treatment by an ophthalmologist is highly effective in slowing or stopping glaucoma’s progression, says Dr. Diaz. Most treatments are aimed at lowering IOP, and each person is different as far as what works best.

The first-line treatment for open-angle glaucoma is eye drop medication, and there are about 20 different kinds that may be prescribed alone or in combinations, he says. Different types of eye drops do different things, such as decrease the buildup or reduce production of fluid in the eye; other drops increase the flow of fluid out of the eye.

The success of treatment with eye drops depends on whether you follow directions consistently, so missed doses can be a serious issue, Dr. Diaz says. If an individual isn’t experiencing symptoms, treatment may not be top of mind, he says. Or they may find it difficult to administer drops that need to be given multiple times a day, he adds. For that reason, Dr. Diaz tries to keep patients on once-a-day drops for as long as possible—unless the medication is not working well for them, and they need to try a kind that requires more frequent doses.

If glaucoma progresses even with prescription eye drops, there are oral medications that can reduce IOP, but they can be less effective, Dr. Diaz says. “We use those only in rare circumstances and in addition to the eye drops, never instead of them,” he says. “For instance, if a patient who has already tried four types of eye drops still wants to take steps to avoid surgery to treat the condition, they may try a pill,” he says.

Surgical procedures can be used to reshape tissue to normalize the flow of fluid in the eye. The biggest advancement in glaucoma surgery is minimally invasive glaucoma surgery (MIGS), which can usually be performed in an ophthalmologist’s office. There are several kinds.

An increasingly popular MIGS combines glaucoma surgery with cataract surgery. It involves placing a small stent (or tube) that bypasses the area where there is drainage resistance so the fluid can flow properly. “Placing the stent only adds a couple of minutes to the surgery, and the patient comes out of the surgery like anybody else who had cataract surgery,” Dr. Diaz says.

For some patients, different outpatient laser treatments may be used to help drain fluid in the eye and lessen eye pressure in both open-angle and closed-angle glaucoma. One such treatment that is helpful for some people is a laser trabeculoplasty, a short, usually painless procedure that involves projecting a strong beam of light through a special lens into the eye to stretch drainage holes.

Traditional surgery performed in a hospital or surgery center may be necessary for some patients with advanced glaucoma. This includes procedures such as a trabeculectomy, which creates a new pathway in the eye through which fluid can drain; another option is glaucoma tube implant surgery, in which a plastic or acrylic tube is implanted and connected to a shunt that carries the fluid out of the eye. While these surgeries are proven to be highly effective, they have higher risks of complications such as scarring and infection.

You can’t prevent glaucoma, but you can detect it early. “It is critical to get your eyes examined, even if you feel fine, because there are eye conditions that may be totally asymptomatic, and for glaucoma early diagnosis and treatment can prevent permanent vision loss later,” Dr. Diaz says.

Experts recommend that everyone should have a complete eye exam by age 40—or sooner if they are at high risk for glaucoma—and ask the doctor for guidance on the frequency of follow-up exams. Medicare covers glaucoma screenings once a year for people with certain risk factors, including diabetes or a family history of glaucoma, or being Black and age 50 or older, or Hispanic and age 60 or older. If you have other health insurance, check with your provider for details on coverage of eye exams.

If you have glaucoma, remember that it’s also critical to consistently follow your treatment plan—even if you are not experiencing symptoms, Dr. Diaz adds.