Diminished Vision: Why Your Eyesight Is Getting Worse

What diminished vision feels like

People describe it as:

• blurred or fuzzy vision, at distance, near, or both
• needing to hold things further away to read
• glare and haloes around lights, especially when driving at night
• colors looking faded or yellowed
• a smudge, gray patch or distortion in the center of vision
• bumping into things or missing steps from side vision loss
• needing brighter light for close work

Doctors measure sharpness as visual acuity on a letter chart. "20/20" means you see at 20 feet what a typical person sees at 20 feet. 20/40 means you need to be at 20 feet to read what a typical person reads at 40 feet. In most US states, 20/40 in the better eye with glasses is the minimum for an unrestricted driver's license.

Common causes of gradually diminished vision

Refractive errors

The most common cause of blurred vision at any age is needing glasses:

• Myopia (nearsightedness): blurry distance vision.
• Hyperopia (farsightedness): difficulty focusing up close, and sometimes distance blur and eyestrain.
• Astigmatism: blurred or stretched vision at all distances.
• Presbyopia: difficulty reading close print, starting around age 40 to 45 as the lens stiffens.

The clue is that vision clears when you look through a pinhole or use the right glasses.

Cataract

A cataract is clouding of the lens inside the eye. It causes slowly worsening blur, glare from headlights, faded colors and frequent prescription changes. It is the leading cause of reversible vision loss worldwide. Surgery replaces the cloudy lens with a clear artificial one and is very successful.

Age-related macular degeneration

Age-related macular degeneration (AMD) damages the macula, the part of the retina used for detailed central vision. It causes blurred or distorted central vision, difficulty reading and recognizing faces, while side vision stays normal. The "dry" form progresses slowly. The "wet" form can worsen quickly and is treated with injections into the eye.

Glaucoma

Glaucoma damages the optic nerve, usually with raised eye pressure. The common open-angle type is painless and steals side vision first, so most people notice nothing until it is advanced. Regular eye exams are the only way to catch it early. Vision lost to glaucoma cannot be restored, but treatment stops further loss.

Diabetic eye disease

Diabetic retinopathy damages retinal blood vessels. Swelling of the macula (diabetic macular edema) blurs central vision. Bleeding inside the eye causes sudden floaters or loss. Annual dilated eye exams are recommended for everyone with diabetes.

Other causes

• Dry eye: fluctuating blur that improves with blinking.
• Medicines: steroids (cataract, glaucoma), hydroxychloroquine (retina), some antihistamines and antidepressants (near focus).
• Changing blood sugar: high blood sugar temporarily changes the lens and blurs vision.
• Corneal conditions: keratoconus and Fuchs' dystrophy.
• Brain and optic nerve conditions: pituitary tumors, multiple sclerosis (optic neuritis) and raised pressure in the skull.

Gradual vs sudden vision loss

For sudden or severe loss of sight, see vision loss.

How eye doctors find the cause

An optometrist or ophthalmologist will:

1. measure visual acuity in each eye, with and without glasses, and with a pinhole
2. check your glasses prescription (refraction)
3. test side vision (visual fields)
4. measure eye pressure
5. examine the front of the eye and lens with a slit lamp
6. dilate the pupils to examine the retina and optic nerve
7. order imaging such as optical coherence tomography (OCT), a scan of the retina's layers, when macular or optic nerve disease is suspected

Checking each eye separately matters. One eye can lose vision for a long time without you noticing, because the other compensates. Cover one eye at a time at home to check.

Treatment

• Glasses or contact lenses for refractive errors, and reading glasses for presbyopia. Laser refractive surgery is an option for some.
• Cataract surgery when cataracts interfere with daily life.
• Anti-VEGF injections for wet AMD and diabetic macular edema. AREDS2 vitamin supplements slow intermediate dry AMD.
• Eye drops, laser or surgery for glaucoma.
• Blood sugar, blood pressure and cholesterol control to protect the retina in diabetes.
• Low-vision aids such as magnifiers, bright task lighting, large print, screen readers and phone accessibility features for vision that cannot be fully restored.

Protecting your vision

• Have a full eye exam every 1 to 2 years after 40, or as advised. People with diabetes need one at least yearly.
• Do not smoke. Smoking raises the risk of cataract and AMD.
• Wear UV-blocking sunglasses outdoors.
• Use protective eyewear for sports and DIY.
• Know your family history of glaucoma and AMD.

Frequently asked questions

Why is my vision getting worse?

The most common reasons are needing glasses or a stronger prescription, age-related reading difficulty (presbyopia), and cataracts. Macular degeneration, glaucoma and diabetic eye disease are other important causes. An eye exam can tell which is responsible.

Can diminished vision be reversed?

Often yes. Glasses, contact lenses and cataract surgery restore vision in many people. Treatment for wet macular degeneration and diabetic macular edema can stabilize and sometimes improve vision. Vision already lost from glaucoma or advanced retinal damage usually cannot be restored.

Is blurry vision a sign of diabetes?

It can be. High blood sugar can blur vision by changing the shape of the lens, and long-standing diabetes can damage the retina. If you have new blurry vision with thirst, frequent urination or weight loss, ask for a blood sugar test.

How often should I have my eyes checked?

Adults without symptoms should have a baseline eye exam by age 40 and then every 1 to 2 years, or as advised. People with diabetes, glaucoma risk factors or existing eye conditions need more frequent checks.

When is diminished vision an emergency?

Go to the ER for sudden vision loss, a shadow or curtain over your vision, a shower of new floaters or flashes, or a painful red eye with blurred vision. Call 911 if vision loss comes with stroke symptoms.