Vision Changes: Causes and When to Worry

Types of vision changes

Gradual vision changes

Refractive errors and presbyopia

Refractive errors (nearsightedness, farsightedness and astigmatism) cause blurry vision at distance, near or both, and are corrected with glasses, contacts or laser surgery. After about age 40, the lens stiffens and close-up focus becomes harder (presbyopia).

Cataract

A cataract is clouding of the eye's lens. It causes gradual blurring, glare and halos, especially when driving at night, faded colors, and frequent changes in glasses prescription. Surgery replaces the cloudy lens and is highly successful.

Glaucoma

Glaucoma damages the optic nerve, usually from high eye pressure. The common type causes no symptoms until side vision is lost, which cannot be restored. Regular eye exams catch it early.

Macular degeneration

Age-related macular degeneration affects central vision, causing blurring, distorted straight lines and difficulty reading or recognizing faces. The wet form can progress quickly and is treated with injections into the eye.

Diabetic eye disease

Diabetic retinopathy damages retinal blood vessels. It is often silent until advanced. High blood sugar can also cause fluctuating blur by swelling the lens. People with diabetes need a dilated eye exam every year.

Other gradual causes

• dry eye, causing blur that clears with blinking
• medicines such as steroids (cataract, glaucoma), hydroxychloroquine (retinal damage) and antihistamines (dry eye)
• keratoconus, a thinning, cone-shaped cornea in younger people

Sudden vision changes

Retinal detachment

Retinal detachment causes a sudden increase in floaters, flashes of light, and a shadow or curtain moving across the vision. It needs surgery within hours to days to save sight.

Retinal vascular occlusions

A blocked artery to the retina causes sudden, painless, severe vision loss in one eye. It is an "eye stroke" and needs the same emergency assessment as a stroke. A blocked vein, such as a branch retinal vein occlusion, causes sudden blurred or patchy vision, usually less severe.

Optic neuritis

Optic neuritis is inflammation of the optic nerve, most often in adults aged 20 to 45. It causes blurred vision over hours to days, pain on moving the eye, and faded colors. It can be the first sign of multiple sclerosis.

Stroke and TIA

A stroke can cause loss of vision on the same side in both eyes, double vision, or sudden blindness in one eye. Brief, temporary loss of vision in one eye (amaurosis fugax) is a warning sign of stroke.

Acute angle-closure glaucoma

A sudden rise in eye pressure causes a red, painful eye, blurred vision, halos, headache, nausea and vomiting. It is an emergency.

Giant cell arteritis

In people over 50, inflamed arteries can cut off blood to the optic nerve, causing sudden permanent vision loss. Warning signs include headache, scalp tenderness and jaw pain when chewing.

Other sudden causes

• migraine aura: shimmering zigzag lines lasting 5 to 60 minutes, usually followed by headache
• very high blood pressure or preeclampsia
• low blood sugar
• eye infections and inflammation (keratitis, uveitis)
• head or eye injury

How eye doctors evaluate vision changes

An optometrist or ophthalmologist will check your vision on a chart, eye pressure, pupils, eye movements, and side vision, and look at the front and back of the eye after dilating drops. Additional tests may include:

• OCT (optical coherence tomography): a scan of the retina and optic nerve layers
• visual field testing for glaucoma, stroke or pituitary problems
• fluorescein angiography to show blood vessel problems
• blood tests for diabetes, inflammation (ESR, CRP) and cholesterol
• MRI of the brain for optic neuritis, stroke or unexplained double vision

Treatment

Treatment depends on the cause:

• glasses, contacts or refractive surgery
• cataract surgery
• pressure-lowering eye drops, laser or surgery for glaucoma
• anti-VEGF injections for wet macular degeneration, macular edema and some vein occlusions
• laser or surgery for retinal tears and detachment
• steroids for optic neuritis and giant cell arteritis
• treatment of diabetes, blood pressure and cholesterol to protect the retina

Protecting your vision

• Have a comprehensive eye exam every 1 to 2 years after 40, or as advised. More often with diabetes, high eye pressure or a family history of glaucoma.
• Wear UV-blocking sunglasses and protective eyewear for sports and DIY.
• Stop smoking, which raises the risk of cataract and macular degeneration.
• Keep blood sugar, blood pressure and cholesterol under control.

Frequently asked questions

When should I worry about vision changes?

Seek emergency care for sudden vision loss, a curtain or shadow over your vision, a burst of new floaters and flashes, sudden double vision, or vision changes with severe headache, eye pain, or stroke symptoms. Gradual changes should be checked at a routine eye exam.

What causes sudden blurred vision?

Sudden blurred vision can come from retinal problems, optic neuritis, acute glaucoma, stroke, migraine, very high blood pressure, low blood sugar or an eye infection. Some causes threaten sight, so sudden blurring needs same-day assessment.

Can stress or tiredness cause vision changes?

Tiredness and long screen use can cause eye strain, dry eyes and temporary blurring that improves with rest and blinking. Stress can trigger migraine aura. Persistent or sudden changes should not be blamed on stress until an eye exam has been done.

Can high blood sugar cause blurry vision?

Yes. High blood sugar can swell the eye's lens and cause blurring that comes and goes. Over years, diabetes damages the retina (diabetic retinopathy), which can cause permanent vision loss. Annual dilated eye exams catch it early.

Can vision changes be a sign of a stroke?

Yes. Sudden loss of vision in one eye, loss of the same side of vision in both eyes, or sudden double vision can be signs of a stroke or TIA. Call 911 or your local emergency number, especially if there is face droop, arm weakness or slurred speech.