In short
Cataracts and glaucoma are both common causes of sight loss in older adults, and they are often mixed up — but they are very different. A cataract is a clouding of the eye's lens; it causes blurry, dim vision and is reversible, because surgery to replace the lens usually restores sight. Glaucoma is damage to the optic nerve, usually from raised pressure in the eye; it tends to take side (peripheral) vision first, often with no early symptoms, and the sight it takes cannot be brought back — though treatment can stop it getting worse. The key difference: cataract surgery restores lost vision, while glaucoma treatment protects the vision you still have. Regular eye tests detect both.
When eye symptoms need urgent help
In the UK, go to A&E or call 999 if you suddenly cannot see or develop sudden severe eye pain. Do not drive yourself. For new vision changes, a dark shadow, or a red or painful eye, seek an urgent GP appointment or NHS 111 advice. Elsewhere, use your local urgent care service.
NHS guidance on vision lossWhen to see a doctor
Have your eyes checked by an optometrist or GP if you notice:
- Cataract: gradually cloudy or blurry vision, glare and haloes around lights, faded colours
- Glaucoma (chronic): usually NO early symptoms — regular eye tests are the only reliable way to catch it
- Glaucoma: patchy loss of side (peripheral) vision
- URGENT (acute glaucoma): sudden severe eye pain, headache, nausea, redness and haloes — seek emergency eye care
- The single best protection against both is a regular eye test
Regular eye tests detect many sight-threatening conditions before you notice symptoms. For sudden vision loss or severe eye pain, seek urgent medical help.
Cataracts and glaucoma are two of the most common causes of sight loss, especially in older adults, and because both can blur or reduce vision they are frequently confused. Understanding how they differ matters, because the outlook and the treatment are very different — and in one case, acting early is the only way to protect sight.
In short: a cataract clouds the lens and is reversible with surgery, while glaucoma damages the optic nerve and causes permanent loss that treatment can only slow. This guide sets the two side by side so the difference is clear.
Cataracts vs glaucoma: the key differences
The simplest way to tell them apart is by what they affect and whether the sight loss can be reversed. Cataracts affect the eye's lens and are reversible; glaucoma affects the optic nerve and is not.
How cataracts and glaucoma compare
| Cataracts | Glaucoma | |
|---|---|---|
| What it affects | The eye's natural lens (it clouds over) | The optic nerve (usually from raised eye pressure) |
| Early symptoms | Cloudy/blurry vision, glare, faded colours | Usually none — it is often symptomless at first |
| Vision lost first | Overall clarity becomes dim and blurry | Side (peripheral) vision, often unnoticed |
| Can sight be restored? | Yes — surgery usually restores vision | No — lost sight is permanent, but treatment slows further loss |
| Main treatment | A short operation to replace the cloudy lens | Eye drops, laser, or surgery to lower eye pressure |
| If left untreated | Can cause blindness — but it is treatable | Can cause permanent, irreversible blindness |
Can you have both at the same time?
Yes. Both conditions become more common with age, so it is entirely possible to have cataracts and glaucoma together. They are managed separately — cataract surgery to restore the clouded lens, and ongoing treatment to control glaucoma — and an eye specialist will plan care for both. Having one does not cause the other, although they can occasionally be linked through certain treatments or eye conditions.
Help someone reach eye care
About £200 is our planning estimate for one cataract operation. Any amount contributes to the Gift of Sight Appeal, and outcomes vary by condition.
Donate to eye careHow both are detected
Crucially, both cataracts and glaucoma are picked up by a routine eye test, often before they cause obvious problems. Because chronic glaucoma has no early warning signs, a regular eye examination is the single most important thing you can do to protect your sight — it can catch glaucoma early enough to prevent serious loss, and identify cataracts when surgery can restore clear vision.
In many parts of the world, that simple eye test and the treatment that follows are out of reach. World Aid Network funds sight-restoring eye care through locally-licensed surgeons for people who cannot afford it.
Key takeaways
- Cataracts cloud the lens and are reversible; glaucoma damages the optic nerve and causes permanent loss.
- Cataract surgery restores lost sight; glaucoma treatment protects the sight you still have.
- Cataracts blur overall vision; glaucoma usually takes side vision first, often with no early symptoms.
- You can have both conditions at once, and they are treated separately.
- A routine eye test detects both — it is the best protection, especially for symptomless glaucoma.
Help someone reach eye care
About £200 is our planning estimate for one cataract operation. Gifts go to the Gift of Sight Appeal’s wider eye-care fund. Outcomes vary by condition, and some care aims to preserve remaining vision rather than restore sight already lost.
Frequently asked questions
What is the main difference between cataracts and glaucoma?
A cataract is a clouding of the eye's lens that causes blurry, dim vision and is reversible — surgery to replace the lens usually restores sight. Glaucoma is damage to the optic nerve, usually from raised eye pressure, which takes side vision first and causes permanent loss that treatment can only slow. In short: cataract surgery restores vision, while glaucoma treatment protects remaining vision.
Which is worse, cataracts or glaucoma?
In terms of long-term risk, glaucoma is generally more serious because the sight it takes cannot be restored — only further loss can be slowed. Cataracts, although they can cause blindness if untreated, are usually reversible with a routine operation. This is why catching glaucoma early, through regular eye tests, is so important.
Can cataracts turn into glaucoma?
No — they are separate conditions affecting different parts of the eye (the lens versus the optic nerve), and one does not turn into the other. However, both are common with age, so many people have both at once, and in some specific situations a very advanced cataract can raise eye pressure. An eye specialist can assess and manage both.
Can you have cataracts and glaucoma together?
Yes. Because both become more common with age, having them together is common. They are managed separately — cataract surgery to restore the clouded lens, and drops, laser or surgery to control glaucoma — and your eye care team will plan treatment for both.
How are cataracts and glaucoma diagnosed?
Both are usually detected during a routine eye test, frequently before you notice symptoms. The test checks vision, eye pressure and the health of the optic nerve and lens. Because chronic glaucoma has no early symptoms, regular eye examinations are the only reliable way to catch it in time.
About this information
Published by World Aid Network with editorial oversight by Kaiser Khan. This is a summary of published information, not a diagnosis. A named clinician has not signed off this version. Discuss your sight with an optometrist, GP or eye specialist.
What are the sources for this guide?
Follow the original guidance for its evidence, dates and limitations. General background references are not a clinical review of this page.