Diagnosing Glaucoma

Glaucoma is a progressive and degenerative disease of the optic nerve. Left untreated, it can cause vision loss. The optic nerve is responsible for transmitting images received by the eye’s retina, a light-sensitive layer of tissue, to your brain. As the nerve degenerates, it can lead to vision loss, mainly of peripheral, or side, vision, but also possibly in central areas of your vision. Central vision allows you to see directly ahead. 

There is no cure for glaucoma, but if it's detected early, NYU Langone specialists can help you manage the condition and preserve your eyesight.

When pressure in your eye, known as intraocular pressure, is too high, it can lead to glaucoma. However, some people can develop glaucoma with a normal pressure in the eye. 

The front part of the eye is filled with a clear fluid called aqueous humor. Normally, this fluid flows in and out of the eye through a drainage system located at an angle where the iris—the colored part of the eye—meets the cornea, the transparent, dome-like structure on the front of the eye.

Proper drainage keeps eye pressure at a normal level. If the drainage system doesn’t work properly, the fluid can’t filter out of the eye at a normal rate, causing a buildup. This increased buildup and pressure against the optic nerve can ultimately damage it, causing glaucoma.

Types of Glaucoma

There are two main forms of glaucoma: open angle and angle closure.

Open Angle Glaucoma

Open angle glaucoma is a chronic form of the condition—and the most common one. In this type, the angle at which the drainage occurs in the eye is working properly, but the fluid is draining too slowly. 

Most people with open angle glaucoma don't experience any symptoms until irreversible vision loss occurs, which is why regular eye exams are very important. Once diagnosed, open angle glaucoma requires long-term treatment. 

Angle Closure Glaucoma

In angle closure glaucoma, the less-common type, the iris is pulled or pushed up against the angle formed by the cornea and the iris, blocking the drainage system of the eye and causing fluid and pressure to build. This usually occurs in people with smaller eyes, where there is not enough room for fluid to circulate. 

Angle closure glaucoma can be acute or chronic. In the acute form, symptoms come on suddenly and may include blurry vision, halos around lights, intense eye pain, or all three. This type of the condition is considered a medical emergency and requires immediate treatment.

In the chronic form, the pressure may build very slowly, which is less painful but can be more difficult to detect. 

Glaucoma Risk Factors

The cause of glaucoma is not known, but there are numerous risk factors associated with the disease. Genetics play a role, because glaucoma runs in families, and people over age 60 are at higher risk of developing eye diseases in general. Certain ethnic groups—including African Americans, Hispanics, and Asians—are statistically at a greater risk for glaucoma than the rest of the population. 

People who have trouble controlling their blood pressure could be at risk, because high blood pressure and low blood pressure can affect how much blood enters the eye. Also, some eye medications can affect blood pressure, and some blood pressure medications can affect eye pressure. Our doctors recommend that people with high or low blood pressure have an annual eye exam to check for glaucoma.

Myopia, or nearsightedness, puts you at higher risk for open angle glaucoma because the shape of the eye may put additional stress on the optic nerve. People with type 1 and type 2 diabetes should be watchful because diabetes can be associated with cataracts, glaucoma, and diabetic retinal disease. People with diabetes should have an annual eye examination.

Autoimmune diseases, such as sarcoidosis, multiple sclerosis, and systemic lupus erythrematosis, can also be associated with a variety of eye problems. That’s because the medications used to treat these conditions, including steroids, can cause cataracts and glaucoma. Others with inflammatory eye diseases, including uveitis, should have their eyes monitored eyes carefully for signs of glaucoma.

Screening for Glaucoma

Although you can’t prevent glaucoma, early detection and treatment can slow or even stop progression of the disease and prevent potential complications. After age 60, when the chances of developing glaucoma increase, doctors recommend having an eye exam every year. 

If you belong to a high-risk group for glaucoma—which includes African Americans, Hispanics, people with a family history of glaucoma, and those who have diabetes—your doctor may want to begin screening before age 60 to ensure early detection. 

Diagnostic Tests

To diagnose glaucoma, NYU Langone ophthalmologists assess the state of the optic nerve. Although intraocular pressure is an important factor in diagnosing and treating glaucoma, having high pressure alone is not enough to confirm the disease. 

Many people who have high eye pressure never develop glaucoma, and half of those diagnosed with glaucoma do not have markedly high eye pressure. 

When performing diagnostic tests, your doctor examines the pressure in your eye, assesses the structure of the optic nerve, and evaluates your vision and whether it has been affected. 

Tonometry

During a tonometry exam, also known as intraocular pressure measurement, doctors use eye drops to numb the eye, then use a device called a tonometer to measure the pressure inside the eye. 

This device gently presses against the eye to estimate the pressure—just as you might gently squeeze a soccer ball to determine whether it needs more air.

Slit-Lamp Exam and Fundoscopy

In a slit-lamp exam and fundoscopy, you place your chin on a soft pad and hold your head steady while your ophthalmologist shines a thin light beam into your eye. The doctor uses this microscope, called a slit-lamp, to gain a close-up look at the cornea, iris, and lens of your eye. 

To examine the back of the eye, or retina, your ophthalmologist dilates your pupils with eye drops. With the pupil dilated, the doctor looks for any abnormalities in the shape or color of the optic nerve—a sign that it may be damaged—and the retina, including the macula. The macula is responsible for central vision. 

An exam called gonioscopy is performed with the slit-lamp, during which the ophthalmologist uses a lens placed on the eye to view the angle between the iris and the cornea to determine if you have glaucoma. 

Visual Field Testing 

During this test, doctors ask you to sit at a machine and look straight ahead and indicate when you can see a moving light in your peripheral, or side, vision. This helps the doctor draw a map of your vision and assess whether any nerve tissue has been damaged.

Optical Coherence Tomography 

Optical coherence tomography is widely used to detect and monitor glaucoma. During this painless test, which is similar to an ultrasound exam but uses light instead of sound waves, your eyes may be dilated. You put your head on a chin rest and hold still while the machine scans your eye with a light beam and takes high-resolution pictures. 

Doctors may perform optical coherence tomography one to six times per year to monitor any changes in the optic nerve or macula over time.

When to Treat Glaucoma

If you are diagnosed with open angle glaucoma, doctors recommend treatment on a case-by-case basis. Before developing a treatment plan, your doctor takes into account several factors. These include the risk of disease progression and potential loss of vision based on the condition of your optic nerve, your age, ethnicity, family history, and other factors and medical conditions you may have.

For mild or borderline glaucoma—meaning an optic nerve that looks somewhat suspicious but still functions—your doctor may want to monitor you indefinitely, until the condition changes or worsens, and then begin treatment. Doctors use the term “glaucoma suspect” to describe people with borderline findings.

Your doctor may also consider treatment if you have family members who have developed a progressive form of the disease. In most people, glaucoma progresses slowly, so doctors may prefer to wait and make sure you are a candidate for treatment before prescribing therapy. 

If glaucoma is moderate to severe, your doctor may want to begin treatment right away to prevent a loss of vision.