How Diabetes, Blood Pressure, and Medications Affect Your Eyes

Your eyes are not separate from the rest of your body. Many common health conditions — and the medications used to treat them — have direct effects on your vision and eye health. Your optometrist can often detect signs of these conditions during a routine exam, sometimes before you notice any symptoms.

How does diabetes affect the eyes?

Diabetes is one of the most well-known causes of eye disease. High blood sugar damages the small blood vessels in the retina over time, leading to diabetic retinopathy — the leading cause of preventable vision loss in Canadian working-age adults.

We have a dedicated article on diabetes and eye health that covers this topic in detail, including OHIP coverage for diabetic eye exams. If you have diabetes, that article is essential reading.

What does high blood pressure do to the eyes?

High blood pressure (hypertension) affects the blood vessels throughout your body, including the delicate vessels in the retina. Over time, elevated blood pressure can cause hypertensive retinopathy — visible damage to retinal blood vessels that your optometrist can detect during a dilated exam.

Uncontrolled hypertension also increases your risk of retinal vein occlusion (a blocked blood vessel in the retina that causes sudden vision loss) and is a significant risk factor for glaucoma. These are conditions where early detection makes a real difference in outcomes.

Can high cholesterol affect my vision?

High cholesterol can cause a grey-white ring around the edge of the cornea called arcus senilis. While this ring itself does not affect vision, it can signal elevated cholesterol levels — particularly in patients under 60.

More seriously, cholesterol plaques can block the small arteries supplying the retina. A retinal artery occlusion causes sudden, painless vision loss in one eye and is a medical emergency. It also signals increased risk of stroke.

How do autoimmune conditions affect the eyes?

Several autoimmune conditions have significant eye involvement:

• Rheumatoid arthritis — can cause severe dry eye, scleritis (painful inflammation of the white of the eye), and corneal thinning
• Lupus — can affect blood vessels in the retina, causing retinal vasculitis
• Sjögren's syndrome — one of the most common causes of severe, chronic dry eye
• Multiple sclerosis — optic neuritis (inflammation of the optic nerve) is sometimes the first sign

If you have any autoimmune condition, regular eye exams help catch complications before they cause permanent damage.

What about thyroid disease?

Graves' disease, the most common cause of hyperthyroidism, can cause the muscles and tissues around the eyes to swell — a condition called thyroid eye disease. Symptoms include bulging eyes, double vision, dryness, light sensitivity, and in severe cases, pressure on the optic nerve.

Thyroid eye disease can progress even after thyroid levels are controlled. If you have Graves' disease, let your optometrist know so they can monitor for early changes.

Which medications affect the eyes?

Many commonly prescribed medications have known effects on the eyes:

Corticosteroids (prednisone, dexamethasone) — long-term use raises intraocular pressure and accelerates cataract formation. Even steroid eye drops, inhalers, and skin creams carry some risk.

Hydroxychloroquine (Plaquenil) — widely used for lupus and rheumatoid arthritis, but can cause irreversible retinal toxicity. The Canadian Ophthalmological Society recommends baseline screening and annual retinal exams after five years of use.

Tamoxifen — used in breast cancer treatment, can cause crystalline deposits in the retina and macular changes.

Blood thinners (warfarin, apixaban, rivarelbain) — increase the risk of retinal and subconjunctival hemorrhages.

Dry eye triggers — antihistamines, certain antidepressants (SSRIs, tricyclics), and some blood pressure medications (beta-blockers, diuretics) can all reduce tear production and worsen dry eye symptoms.

Why should I tell my optometrist about all my medications?

Your optometrist cannot monitor for medication side effects they do not know about. Bring a complete, up-to-date list of all your medications — including over-the-counter drugs and supplements — to every eye exam.

Some medication-related eye changes develop slowly and without symptoms. Without the right context, your optometrist may not know to look for them. A complete health history is one of the most important things you can bring to your appointment.