What Ophthalmologists Look for When Diagnosing Glaucoma

Baptist Eye Surgeons • December 11, 2017

Glaucoma is an eye disorder that can occur when the pressure inside your eye rises above normal ( ocular hypertension) and damages your optic nerve. If left untreated, glaucoma can cause you to lose your peripheral vision and even go blind. Read more about what causes glaucoma and how it affects your eyes.

In fact, glaucoma is the second leading cause of blindness in the United States and affects more than 2.7 million people ages 40 and older. Because glaucoma presents with very few (if any) initial symptoms, nearly half of those who have glaucoma don’t even know it ( American Academy of Ophthalmology). This is one of the many important reasons to schedule an ophthalmologist appointment every year, especially if you’re over 40, are diabetic, and/or have a family history of glaucoma.

When conducting a comprehensive glaucoma exam, your doctor will test different parts of your eyes to look for any abnormalities in your inner eye pressure, the shape and color of your optic nerve, your complete field of vision, the angle in the eye where the iris meets the cornea, and the thickness of the cornea itself.

Gauging Your Inner Eye Pressure

A man is getting his eyes examined by an ophthalmologist During tonometry, your ophthalmologist will measure the pressure within your eye with a tonometer. After applying numbing eye drops, he will then administer a small amount of pressure to your eye with a tiny device.

Normal eye pressure typically ranges from 12-21 mm Hg (a scale used to record eye pressure). Most glaucoma cases are diagnosed if the levels exceed 22 mm Hg, but because eye pressure is unique to each person, even those whose levels are as low as 12 mm Hg may be diagnosed with glaucoma as well.

Examining Your Optic Nerve

An illustration of a person 's brain and optic nerve Your ophthalmologist will used a procedure called ophthalmoscopy to inspect your optic nerve for signs of damage caused by glaucoma. After dilating your pupils with eye drops, he will use special lenses to magnify your optic nerve and examine its shape and color.

A normal optic nerve is round and has a pink color around the rim. There is usually a central depression that is more yellow. An optic nerve that looks suspicious for glaucoma has a larger central depression (also known as the “cup”).

If your eye pressure is high and your optic nerve looks abnormal, your ophthalmologist may recommend one or more of the following diagnostic tests.

Mapping Your Complete Field of Vision

A diagram of a person 's vision shows the standard line of sight Perimetry is a visual field test that helps your ophthalmologist determine whether glaucoma has impacted your vision. During the exam, your ophthalmologist will ask you to look straight ahead and indicate when you see a light in your peripheral vision. Your ophthalmologist will then be able to draw a map of your complete field of vision using your responses. You may be asked to repeat the test to verify the results before your ophthalmologist makes a positive diagnosis.

If you are diagnosed with glaucoma, this test will be performed once or twice a year in addition to your regular eye exam to check for any changes in your vision.

Assessing Your Angle

A drawing of a person looking through a telescope A gonioscopy is a fancy name for an exam that ophthalmologists use to measure the angle where the iris and the cornea meet. This angle will be described as open and wide or narrow and closed. After applying numbing eye drops, your ophthalmologist will gently place a special hand-held contact lens on your eye. The mirror on this contact lens will show your ophthalmologist whether the angle between the iris and the cornea is narrow and closed (signifying angle-closure, acute glaucoma) or open and wide (signifying open-angle, chronic glaucoma).

Measuring Your Thickness

A person is holding a device that says ' peach pen ' on it The thickness of your cornea can influence eye pressure readings, so your ophthalmologist may measure it using a pachymetry test. He can do this by simply placing a probe on the front part of your eye (the cornea) that will measure its thickness in under a minute—quick and painless. After knowing the thickness of your cornea, your ophthalmologist can better understand your intraocular pressure (IOP) readings and develop a treatment plan that’s right for you.

If you’re over 40, are diabetic, and/or have a family history of glaucoma and have not had a comprehensive eye exam this year, our ophthalmologists would be happy to see you. Just fill out this online form or call 865-579-3920 to schedule an appoint at our Knoxville or Morristown location.

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Night Vision Problems: Causes and When to See an Eye Doctor

June 30, 2026

Night vision problems can make everyday activities like driving at dusk, walking in poorly lit places, or adjusting to indoor lighting harder and sometimes unsafe. Trouble seeing in low light, called nyctalopia, is not a disease itself but a sign that something else may be affecting your eyes. Learning what causes night vision problems and when to get help is important for keeping your vision healthy. What Are Night Vision Problems? Night vision problems mean it is hard to see clearly in low light or darkness. Some people notice their eyes take longer to adjust when going from bright to dim places. Others may have trouble with glare from headlights, seeing less contrast, or things just looking dimmer at night. Mild changes in night vision can happen as you get older, but if your symptoms keep getting worse or do not go away, you should pay attention to them. Common Causes of Night Vision Difficulties There are several potential causes of night vision problems. Night vision problems can have many causes, from getting older to certain eye conditions, such as lens problems, leading to blurred vision and increased sensitivity to glare. They are one of the most common causes of poor night vision, especially in older adults. 1. Cataracts Cataracts cause clouding of the eye’s natural lens, leading to blurred vision and increased sensitivity to glare. They are one of the most common causes of poor night vision, especially in older adults. 2. Vitamin A Deficiency Vitamin A is important for keeping your retina healthy. If you do not get enough vitamin A, your eyes may have trouble adjusting to darkness, which can lead to night blindness. 3. Glaucoma Some types of glaucoma can affect your side vision and make it harder to see differences between light and dark. As the optic nerve gets damaged, seeing in low light can become more difficult. 4. Retinitis Pigmentosa This inherited eye condition slowly affects your ability to see at night and to the sides. Early signs often include trouble seeing in the dark. 5. Diabetes-Related Eye Disease Diabetic retinopathy can harm the blood vessels in your retina, which may cause blurry vision and make it harder to see at night. 6. Aging and Pupil Changes As people get older, their pupils do not react to light changes as quickly, and the retina becomes less sensitive. This naturally makes night vision worse over time. Symptoms to Watch For Night vision problems often develop slowly. Some common signs are: Difficulty seeing in low light or darkness Trouble driving at night due to glare from headlights Longer adjustment time when moving between light and dark environments Reduced contrast or clarity in dim settings Frequent squinting or eye strain in low light If these symptoms start to affect your daily life, it is a good idea to get a full eye check-up. When to See an Eye Doctor You should see an eye doctor if you notice new night vision problems, if they are getting worse, or if you have other changes in your vision. The doctor can run tests to find out what is causing the problem and suggest the right treatment. A full eye exam might include checking your retina, testing your field of vision, and taking images to look at your eye health. Finding problems early is very important for conditions like glaucoma, diabetic eye disease, and retinal disorders, because early treatment can help protect your vision. Protecting Your Night Vision Not all causes of night vision loss can be prevented, but taking care of your eyes can lower your risk and help you see better. Some helpful steps are: Scheduling regular eye exams Handling chronic health conditions like diabetes Eating a diet rich in vitamin A and antioxidants Wearing proper corrective lenses if prescribed Avoiding driving with untreated vision changes Prioritizing Your Eye Health Night vision problems can be an early sign of eye disease. Since many eye problems develop slowly, having regular eye exams is one of the best ways to catch changes early and keep your vision healthy for the long term. If you have trouble seeing at night or notice any changes in your vision, making an appointment for an eye exam can help keep your eyes healthy and your vision clear in all types of light.

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