“If someone has had an episode of really high blood pressure, there might be some bleeding in the eye,” says Liesl Forward, optometrist and manager at the Australian College of Optometry’s Eye Health Victoria. “But with even chronic low-grade blood pressure, we can see some structural changes to the blood vessels in the retina.

“We might see that they’re narrowed or becoming thickened, or even the more subtle start of that, which alerts us to the fact that the blood pressure is probably higher than it should be.”

2. Stroke

While the eyes can reveal early changes linked to stroke risk, the sudden acute onset of double vision, blurry vision or total loss of vision in one or both eyes can be the first warning sign of an actual stroke. Symptoms may last a few seconds, hours, or longer depending on the area of the brain affected.

“Sudden changes in vision, especially loss of part of your peripheral vision, can indicate that a stroke has occurred,” says Koh. “Because the eyes connect directly to the brain, they can be one of the first places where these issues appear.”

3. High cholesterol

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While there’s some overlap between high cholesterol and high blood pressure in terms of changes to the blood vessels at the back of the eye, you may also notice some changes in the mirror.

“Some people with high cholesterol will see a light coloured ring around the coloured part of their eye. This can happen naturally with age, but sometimes it can indicate that cholesterol is a bit high as well,” says Forward. “It’s on the cornea, which is the clear window, but at a glance it will look as if it’s part of the coloured ring.”

The ring is actually a deposit of fat and, while common in older people, it is more of a cause for concern if you are under 40.

4. Diabetes

An eye exam can pick up early signs of diabetes before you even realise something’s wrong. Optometrists are sometimes the first health practitioner to pick up diabetes, even before the GP does.

“High blood sugar can damage the tiny blood vessels in the retina,” says Koh. “An optometrist can detect this during a routine eye examination just by taking a few seconds to look into your eye with a high-powered microscope, and taking a photo to show you. You may not notice any symptoms at all, but these signs at the back of your eye, such as tiny leaks or blisters in your blood vessels can be a warning sign.”

When diabetes is left untreated, it can lead to diabetic retinopathy, resulting in impaired vision or even loss of sight. Catching these early means you can manage your blood sugar and protect your vision before any long-term damage occurs.

5. Thyroid issues

If you have an overactive thyroid, an optometrist may well spot side effects in your eyes, such as a thickening to the fatty tissue around the eyes, and a thickening of the eye muscles that control eye position. Enlarged, bulging eyes might be a sign of a condition called Grave’s disease, a type of hyperthyroidism that affects the thyroid gland, the eyeball and the eye socket.

“If the eye is more exposed, it can be prone to dryness and irritation,” says Forward. “In extreme cases it can look quite dramatic. If the muscle and fat around the eye is especially congested, it can push on the optic nerve and cause problems with your vision.”

6. Rheumatoid arthritis

Rheumatoid arthritis can affect more than your joints; it can show up in your eyes, too. Optometrists often spot inflammation within the eye that suggests the immune system is attacking more than just the body’s tissues.

“Sometimes these eye changes appear before people realise they have rheumatoid arthritis,” says Koh. “A quick check can help point someone toward the correct diagnosis and treatment sooner, which makes a huge difference.”

7. Other autoimmune diseases

Autoimmune conditions often leave visible clues in the eyes. With multiple sclerosis, for example, one of the earliest signs can be optic neuritis, an inflammation of the optic nerve at the back of your eye that causes blurred vision or pain when moving your eyes.

“This can be the first symptom someone notices,” says Koh. “Lupus and similar conditions can also inflame different parts of the eye. An optometrist can see signs of this inflammation using a microscope during a routine eye exam and help guide someone to further testing if needed.

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8. Migraine

The most common cause of flashing lights in your vision (apart from flashing lights) is migraine. Before the headache part settles in, many people experience visual disturbances known as aura. But if you’re not convinced it’s a migraine, you should get it checked out ASAP.

“The main thing we’d be wanting to rule out with flashing light is retinal detachment because if that happens, it can cause a lot of vision loss quite quickly,” says Forward. “That’s one of our true eye emergencies.”

Retinal detachment can be a result of eye trauma, but more often than not is caused by an overstretched retina that suffers a tiny tear that becomes worse over time.

“It’s more common for people who are short-sighted because their eyes are longer than average,” explains Forward. “If we see a retinal detachment, then we’re usually referring you off to have surgery within one or two days.”

9. Computer vision syndrome

If you experience blurry vision, headaches and/or sore eyes during or after screen time, you could be suffering from computer vision syndrome (CVS).

“CVS is something optometrists see quite a bit of these days, and it’s becoming more common in children and teenagers who are using screens at home and at school,” says Forward. “It can go undetected for a while because very young kids might not have much of a point of reference on what normal vision is like, and teens often don’t want to cause a fuss about these things.″⁣
The good news is, CVS rarely causes permanent damage. Your optician will likely discuss modifying your computer habits — taking breaks, repositioning your computer, and blinking more often.

10. Bowel cancer

Did you know some cancers can be picked up during a regular eye exam? Optometrists can spot unusual freckles or lesions inside the eye that you’d never see in the mirror. When optometrists detect these changes, it may suggest tumours elsewhere in your body.

“As an example, a distinctive-looking darkish lesion at the back of the eye is linked to polyps within your gastrointestinal system, which is linked to bowel cancer,” says Koh. “So optometrists play a critical role in detecting these atypical lesions early, so we can then refer you for gastrointestinal screening that will potentially add years to your life.”

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