What an Eye Exam Can Find: Diabetes, High Blood Pressure — Even a Brain Tumor

An eye exam can find signs of diabetes, high blood pressure, high cholesterol, and some autoimmune and nerve conditions. Rarely, it can even find swelling caused by a problem inside the head, such as a brain tumor. The retina is the thin layer of tissue lining the back of your eye. It is the only place in the body where a doctor can see blood vessels and nerve tissue directly, without cutting or scanning.

Why can an eye doctor see so much?

Picture the retina as the movie screen at the back of your eye. Tiny arteries and veins run across it, and the optic nerve, which is the cable that carries what you see to your brain, enters right there too.

Everywhere else in the body, those structures are hidden under skin and bone. In the eye, we can see them through the clear front of the eye with a bright light and a magnifying lens. With retinal imaging, we can also take a photo and compare it year to year. OCT is a scan that uses light to show the layers of the retina and optic nerve. It shows changes too small to see any other way.

When those vessels or nerves change, the eye is often one of the first places to show it.

Can an eye exam detect diabetes?

Yes. Diabetes damages small blood vessels, and the ones in the retina are some of the smallest in the body. When they weaken, they can leak fluid or blood or form tiny bulges. This is called diabetic retinopathy.

Early on, diabetic retinopathy usually has no symptoms. Your vision can be 20/20 while changes are happening in the back of your eye. According to the National Eye Institute, diabetic retinopathy is the most common cause of vision loss in people with diabetes, and finding it early gives you the best chance of protecting your sight.

Sometimes we see these changes in a patient who doesn't know they have diabetes yet. When that happens, we ask them to see their primary care doctor so they can get tested. If you already have diabetes, a yearly dilated or imaging-based eye exam is a must. Our diabetic eye care page explains more.

What about high blood pressure and cholesterol?

High blood pressure can narrow and stiffen the arteries in the retina. We may see arteries that look thin, places where an artery presses on a vein, or small bleeds. This is called hypertensive retinopathy. In severe cases, the optic nerve can swell, which is an urgent finding.

High cholesterol can leave clues, too. Sometimes we see a tiny bright cholesterol fleck lodged in a retinal artery. That can mean a piece broke loose from a larger artery, such as the one in the neck. It is linked to a higher risk of stroke, so see your medical doctor promptly. A white or gray ring around the edge of the cornea, the clear front of the eye, can also be a sign of high cholesterol in younger adults.

Can an eye exam find autoimmune or nerve conditions?

It can show signs that lead to the right diagnosis. A few examples:

• Inflammation inside the eye (uveitis) can be tied to conditions such as juvenile arthritis, sarcoidosis or certain types of spinal arthritis.
• Severe dry eye can be part of autoimmune conditions like Sjögren's syndrome.
• Optic neuritis, an inflamed optic nerve, often causes blurry vision and pain when moving the eye. It is sometimes the first sign of multiple sclerosis (MS).

An eye exam does not diagnose these diseases on its own. What it does is notice the clue, so we can send you to the right specialist sooner.

Can an eye exam really find a brain tumor?

It can, but I want to be clear: this is rare. Most of the headaches and blurry vision we see have simple causes.

Still, two findings get our full attention:

• Swollen optic nerves (papilledema). When pressure inside the skull rises, it can push on both optic nerves and make them swell. A tumor is one possible cause. There are others, including a condition where fluid pressure rises without a tumor.
• A specific pattern of side vision loss. A visual field test maps your side vision. Certain patterns, such as losing the same side of vision in both eyes, can point to a problem along the vision pathway in the brain.

When we see either one, we don't guess. We make sure you get the next step quickly, such as brain imaging, and sometimes that means going to the emergency room the same day. The point is not to scare you. A careful look at your eyes can simply lead to answers faster.

Why do dilation, retinal imaging and OCT matter?

A quick vision screening only tells us how well you read letters. It does not look at the health of the back of the eye. To catch the problems in this post, we need a full view of the retina and optic nerve.

• Dilation widens the pupil so we can see more of the retina.
• Retinal imaging gives us a photo to compare over time, which helps us spot slow changes.
• OCT shows the layers of the retina and optic nerve, which is how we find early swelling, fluid or thinning. Learn more on our technology in eye care page.

When should you see an eye doctor?

Call us right away or go to the emergency room if you notice:

• Sudden loss of vision in one or both eyes
• A curtain or shadow moving over part of your vision
• New flashes of light with a shower of new floaters
• Severe eye pain with nausea, headache or halos around lights
• Sudden double vision, or a bad headache with vision changes
• Any chemical splash in the eye

Book a regular exam soon if you have diabetes, high blood pressure or a family history of eye disease, or if it has been more than a year since your last visit. See How Often Should You Get an Eye Exam? for more.

How we do it at Bolt Eye Group

At every Bolt Eye Group office, our comprehensive exams include a full eye-health check, not just a glasses prescription. Every patient also gets retinal photos and corneal topography for a $39 imaging fee. The photos let your doctor confirm that your retina and optic nerve are healthy, and show you what they see. With an in-office telehealth visit, the same $39 also covers two OCT glaucoma scans, one of the optic nerve and one of the macula. You take all your images home free on the I-Scan Platinum Lifetime Baseline, a credit-card-size USB drive. In-office telehealth is available at every office. If something needs attention, we explain what we saw in plain words and help connect you with your primary care doctor or a specialist.

We see patients at five offices: Canton, East Cobb/Marietta, Lawrenceville and Riverdale in Georgia, and Johnson City, Tennessee. We accept VSP, EyeMed, Davis Vision, Spectera, Medicare and major medical plans, including Blue Cross Blue Shield, Aetna, UnitedHealthcare, Cigna and Humana. Visit our eye exam specialist page to see what a full exam includes.

Frequently asked questions

Can an eye exam tell if I have diabetes?

An eye exam can show changes in the retina that are common with diabetes, sometimes before a person knows they have it. It cannot diagnose diabetes by itself. If we see signs, we will recommend you see your primary care doctor for blood testing.

Is a vision screening at school or the DMV the same as an eye exam?

No. A screening checks how well you see letters on a chart. A comprehensive eye exam also checks the health of your eyes, including the retina and optic nerve, which is where many silent problems show up.

Should I worry that my headaches mean a brain tumor?

Most headaches are not caused by a tumor. Eye strain, an outdated prescription, dry eye, sinus trouble and tension are far more common. If you have headaches with vision changes, an eye exam is a good first step, and a sudden severe headache with vision loss needs emergency care.

How often should I get my eyes checked if I have diabetes or high blood pressure?

Most people with diabetes should have an eye exam at least once a year, and some need it more often. If you have high blood pressure, yearly exams help us watch for changes. Your eye doctor will set the right schedule for you.

Book an exam at your nearest Bolt Eye Group office

Your eyes can tell us a lot about your health. Book an exam at your nearest Bolt Eye Group office in Canton, East Cobb/Marietta, Lawrenceville, Riverdale or Johnson City, TN. Find hours and directions on our locations page.