Glaucoma vs Cataracts: Symptoms, Vision Loss and Treatment

Cataracts and glaucoma affect different parts of the eye. A cataract is a cloudy area in the lens, the clear part of the eye that helps focus light, and it can make vision cloudy or blurry and colors look faded. Glaucoma is a group of eye diseases that damage the optic nerve in the back of the eye; it usually has no symptoms at first, then slowly takes side vision. The bigger difference is what happens to lost vision. Surgery can replace a cloudy lens, and 9 out of 10 people see better afterward. Glaucoma treatment can often stop the damage, but it won't undo damage that's already done.

Key takeaways

A cataract clouds the eye's lens and can blur vision, while glaucoma damages the optic nerve at the back of the eye and slowly takes side vision.
Cataract surgery replaces the cloudy lens and 9 out of 10 people see better afterward, but vision already lost to glaucoma can't be restored.
Half of people with glaucoma don't know they have it, and early treatment, usually prescription eye drops, can often stop the damage.
Sudden severe eye pain, especially with a red eye, blurry vision, headache, nausea or halos, means calling immediately for a same-day exam, or an emergency room when we're closed.

What is the difference between glaucoma and cataracts?

A cataract clouds the clear lens inside your eye. Glaucoma damages a nerve in the back of your eye called the optic nerve.

Question	Cataracts	Glaucoma
What it affects	The lens, the clear part of the eye that helps focus light	The optic nerve, in the back of the eye
Early symptoms	None	Often none
Later symptoms	Blurry vision, faded colors, sensitivity to light, trouble seeing at night, double vision	Loss of side (peripheral) vision, blind spots, blindness
How it's found	Dilated eye exam	Dilated eye exam with visual field testing
Treatment	Surgery	Medicine (usually eye drops), laser treatment, surgery
Lost vision	9 out of 10 people see better after surgery	Can't be restored

Table sources: the National Eye Institute on cataracts and glaucoma, and the American Optometric Association on glaucoma.

How does each one change your vision?

A cataract affects how clearly you see. Its symptoms include cloudy or blurry vision, faded colors, poor night vision, glare from lamps, sunlight or headlights, halos around lights, double vision, and frequent changes to your glasses prescription. These usually develop slowly, and our cataracts guide covers them in detail.

Glaucoma affects how much you see, and at first you may not notice. It usually has no early symptoms, and half of people with glaucoma don't know they have it. Over time, vision loss usually starts with side (peripheral) vision, especially the part closest to your nose, and because it happens so slowly, many people can't tell their vision is changing at first.

As it gets worse, it may seem like you're looking through a tunnel. Without treatment, straight-ahead vision may decrease until no vision remains.

Can vision lost to cataracts or glaucoma come back?

With a cataract, usually yes. Surgery is the only way to get rid of one: the surgeon removes the cloudy lens and replaces it with an artificial lens called an intraocular lens, or IOL. Nine out of 10 people who have the surgery can see better afterward.

With glaucoma, no. There's no cure, and treatment won't undo damage that's already done, though early treatment can often stop the damage and protect your vision. The American Optometric Association says vision already lost to glaucoma cannot be restored.

Left untreated, both can take a great deal of sight. Untreated cataracts can cause severe or even permanent loss of vision, and without treatment, glaucoma can eventually cause blindness. The CDC reports that cataract causes more blindness worldwide than any other condition, and AOA ranks glaucoma second among causes of blindness in the U.S.

Who is at risk for glaucoma and cataracts?

Getting older raises the risk of both: cataract risk goes up as you get older, and glaucoma risk is higher over age 60. The National Eye Institute lists these risk factors for each:

Cataracts

Diabetes or certain other health problems
Smoking
Drinking too much alcohol
A family history of cataracts
A past eye injury, eye surgery, or radiation treatment on the upper body
A lot of time in the sun
Steroid medicines

Glaucoma

Being over 60, especially if you're Hispanic or Latino
Being African American and over 40
A family history of glaucoma

Many people with glaucoma have high eye pressure, and AOA adds that some studies suggest high amounts of nearsightedness may also be a risk factor. If you've been told your pressure runs high, our page on ocular hypertension explains how we monitor it.

How are cataracts and glaucoma treated?

For cataracts, a new glasses prescription, brighter lights, anti-glare sunglasses and magnifying lenses can help at first. Surgery is the only way to get rid of a cataract, and your doctor might suggest it once cataracts start getting in the way of everyday activities like reading, driving or watching TV. We handle the care before and after the operation through cataract co-management.

For glaucoma, prescription eye drops are the most common treatment. To lower eye pressure, doctors can also use lasers to help fluid drain out of the eye, and if medicines and laser treatment don't work, your doctor might suggest surgery. Treatment should start right away.

Glaucoma has no cure, but it can usually be controlled, and MedlinePlus advises continuing treatment to prevent your vision from getting worse.

Can you have glaucoma and cataracts at the same time?

Yes, and one can lead to the other. Cataracts can form after surgery for another eye problem, like glaucoma. In the other direction, cataracts can cause glaucoma, though NEI says this isn't as common.

If you've been told your drainage angles are narrow, our narrow angles page explains how they're monitored and where cataract surgery fits in.

When is glaucoma an emergency?

When it comes on suddenly. Cataracts usually develop slowly, and so does open-angle glaucoma, the most common type. Angle-closure glaucoma, also called narrow-angle or acute glaucoma, is a medical emergency: the outer edge of the iris blocks fluid from draining out of the front of the eye, and if it's not treated, it can cause blindness in just a few days.

Its sudden symptoms include intense eye pain, an upset stomach (nausea), a red eye and blurry vision. AOA adds seeing halos or colored rings around lights.

If you suddenly have severe eye pain, especially with a red eye, blurry vision, headache, nausea or halos, call us immediately at 310-828-2010 for a same-day exam during office hours (Monday 10am to 5pm, Tuesday to Friday 8am to 5pm), or go to an emergency room when we're closed. Sudden loss of vision in one or both eyes, even if it comes back, is a 911 call at any hour.

How we check for glaucoma and cataracts at Cohenmehr Optometry

Every comprehensive eye exam here includes a glaucoma screening (eye pressure and an optic nerve evaluation, with OCT nerve-fiber analysis and visual fields when indicated) and a check of the lens, where we grade any cataract.

For glaucoma and glaucoma suspects, we monitor with eye pressure measurements, OCT imaging of the optic nerve, visual field testing and retinal photography, and when necessary, we work with glaucoma specialists for referral and advanced treatment; see our page on glaucoma testing and management. If your eye pressure runs high but your optic nerve is healthy (ocular hypertension), our OHTS glaucoma risk calculator shows how five measurements from a pressure work-up add up to an estimated five-year risk of developing glaucoma.

For cataracts, our Los Angeles eye doctors measure how much the cataract affects your vision and update your glasses while surgery can wait. When it can't, we refer you to a trusted cataract surgeon, and your follow-up visits after surgery happen here.

Questions patients ask

How often do you need a glaucoma test?

It depends on your risk. NEI advises a comprehensive dilated eye exam every 1 to 2 years if you're at higher risk: over 60 (especially if you're Hispanic or Latino), African American and over 40, or with a family history of glaucoma. MedlinePlus adds that people with high blood pressure or diabetes should get a dilated eye exam at least once a year. Every comprehensive eye exam here includes a glaucoma screening, and after 60 we recommend a comprehensive exam at least once a year.

Can steroid eye drops cause glaucoma or cataracts?

They can. The label for difluprednate (Durezol), a corticosteroid eye drop, warns that prolonged corticosteroid use may result in glaucoma and that corticosteroids may cause posterior subcapsular cataracts (cataracts at the back of the lens), and it calls for routine pressure checks when the drop is used for 10 days or longer. NEI lists steroids as a cataract risk factor, and AOA says prolonged use of corticosteroids such as prednisone appears to put some people at risk of secondary glaucoma. Don't stop a prescribed steroid on your own.

What is normal eye pressure?

There's no single number that's normal for everyone. NEI notes that normal eye pressure varies by person, so what's normal for one person could be high for another. Some people with high eye pressure don't get glaucoma, and one type of glaucoma happens in people with normal eye pressure. The amount of pressure your optic nerve can handle is different for each person, and regular dilated eye exams help your provider figure out what level is normal for you.

Does high blood pressure raise your risk of glaucoma?

It may. MedlinePlus says you're at higher risk for glaucoma if you have high blood pressure or diabetes. AOA notes that some studies indicate diabetes, high blood pressure and heart disease may increase the risk of developing glaucoma. One less common type, neovascular glaucoma, happens when the eye makes extra blood vessels that cover the part of the eye where fluid would normally drain; it's usually caused by another medical condition, like diabetes or high blood pressure.

Sources

Written by

Dr. Kevin Cohenmehr, OD

Medical eye care: glaucoma, diabetic eye exams, macular degeneration and eye infections, plus vision therapy for children. A graduate of UCLA and SUNY College of Optometry.

About Dr. Kevin →

Glaucoma vs. Cataracts: What's the Difference?