Cataracts can increase eye pressure, but it depends on the type and stage
Most cataracts do not raise eye pressure at all. A typical age-related cataract—where the lens gradually becomes cloudy—sits in place and causes no change to the fluid pressure inside your eye. However, certain types of cataracts and specific stages of cataract development can increase pressure enough to damage the optic nerve, a condition called secondary glaucoma. The risk is real but not automatic, and it depends on which kind of cataract you have and how advanced it is.
The mechanism is straightforward: when a cataract becomes very dense and swollen, it can physically block the flow of fluid (called aqueous humor) inside the eye. That fluid normally drains through a tiny channel called the trabecular meshwork. If the cataract gets in the way, pressure builds. In rare cases, a cataract can also cause inflammation that damages the drainage system itself, raising pressure further.
Key Takeaways
- Most age-related cataracts do not raise eye pressure, but dense, swollen cataracts can block fluid drainage and cause secondary glaucoma.
- Phacomorphic glaucoma occurs when a mature or overmature cataract swells and physically obstructs the eye's drainage channel.
- Phacolytic glaucoma happens when proteins leak from a very old cataract and clog the drainage system, raising pressure weeks or months later.
- Regular eye pressure checks during cataract monitoring can catch pressure increases early, before they damage your optic nerve.
- Cataract surgery removes the pressure risk entirely by taking out the clouded lens.
Phacomorphic glaucoma: when a swollen cataract blocks drainage
The most common way a cataract raises eye pressure is called phacomorphic glaucoma. This happens when a cataract becomes very dense and swollen—usually a mature or overmature cataract that has been developing for years. The swollen lens physically pushes forward and blocks the drainage channel, trapping fluid inside the eye.
Phacomorphic glaucoma typically develops suddenly. You might notice a sharp rise in pressure over hours or days, often with pain, redness, blurred vision, or halos around lights. The pressure can climb high enough to damage the optic nerve if not treated quickly. The treatment is usually cataract surgery to remove the swollen lens and restore normal fluid drainage. Once the cataract is out, the pressure usually returns to normal within days.
This type of pressure increase is most common in people who have delayed cataract surgery for a long time. If your eye doctor has recommended surgery and you have been waiting, a sudden increase in pressure or pain is a reason to move up your surgery date.
Phacolytic glaucoma: when a cataract leaks protein
Phacolytic glaucoma is a different mechanism and usually develops more slowly. It occurs when a very old or overmature cataract begins to break down and leak proteins into the eye. These proteins are too large to drain through the normal channels, so they accumulate and clog the trabecular meshwork—the eye's drainage system. Pressure rises gradually over weeks or months.
Unlike phacomorphic glaucoma, phacolytic glaucoma does not happen suddenly. You may not notice symptoms until your eye doctor measures your pressure at a routine visit. The treatment is also cataract surgery, which removes the source of the leaking proteins. After surgery, the clogged drainage system usually clears on its own, and pressure normalizes.
Phacolytic glaucoma is less common than phacomorphic glaucoma but can occur even in eyes where the cataract is not particularly swollen or visibly advanced. This is one reason why regular eye pressure checks matter, even if your cataract seems stable.
Why some cataracts raise pressure and others do not
The key difference is density and size. A soft, early-stage cataract takes up little space and does not swell significantly, so it does not obstruct the drainage channel. The lens stays in its normal position, and fluid flows freely. Pressure stays normal.
A dense, mature cataract is much larger and heavier. It swells as it develops, and the swelling can push it forward into the space where fluid needs to drain. The more advanced the cataract, the greater the risk. This is why cataracts that have been present for many years—especially if surgery has been postponed—carry a higher risk of raising pressure.
Inflammation also plays a role. Some cataracts trigger more inflammation than others, and inflammation can damage the drainage system directly, raising pressure independent of the cataract's physical size. This is why your eye doctor may prescribe anti-inflammatory drops if pressure rises alongside a cataract.
How eye doctors monitor for pressure changes
If you have a cataract that your doctor is monitoring rather than operating on immediately, your eye pressure will be checked at each visit. This is a standard part of cataract care. The measurement takes seconds and is painless—your doctor uses a tonometer, a small instrument that gently measures the pressure inside your eye.
Normal eye pressure ranges from about 10 to 21 millimeters of mercury (mmHg), though this varies slightly from person to person. If your pressure is consistently above 21 mmHg or if it rises suddenly, your doctor will investigate whether the cataract is the cause. They may also check your optic nerve with imaging or visual field testing to see whether the pressure has caused any damage.
If pressure does rise, your doctor may recommend surgery sooner than originally planned, or they may prescribe pressure-lowering drops to manage it while you wait. The choice depends on how high the pressure is, how fast it is rising, and whether your optic nerve shows signs of damage.
What happens to pressure after cataract surgery
Cataract surgery removes the source of the pressure problem entirely. Once the clouded lens is out, the drainage channel is clear again, and fluid can flow normally. In phacomorphic glaucoma, pressure typically returns to normal within a few days of surgery. In phacolytic glaucoma, it may take a bit longer—sometimes one to two weeks—as the drainage system clears the accumulated protein.
If your pressure was elevated before surgery, your eye doctor will continue to monitor it for several weeks afterward to confirm it has normalized. In most cases it does. If pressure remains high after surgery, your doctor will investigate other causes of glaucoma, since the cataract is no longer present to explain it.
This is one of several reasons why cataract surgery can be beneficial even if your vision is not severely affected: it eliminates the risk of cataract-related pressure increases and the optic nerve damage that can follow.
When to contact your eye doctor about a cataract and pressure
Contact your eye doctor right away if you have a known cataract and experience sudden eye pain, a sharp drop in vision, redness, or halos around lights. These can be signs of acute pressure increase. Do not wait for a scheduled appointment.
If you have a cataract and have not had your eye pressure checked in the past year, schedule an appointment. Even if you have no symptoms, a pressure check is important, especially if your cataract has been stable for a long time or if your doctor previously recommended surgery that you have delayed.
If your eye doctor has told you that your cataract is raising your pressure, follow their recommendation about surgery timing. Waiting longer increases the risk of optic nerve damage, which is permanent.
Frequently Asked Questions
Can a cataract cause glaucoma?
A cataract can cause secondary glaucoma by raising eye pressure, but only under specific conditions—usually when the cataract is very dense and swollen, or when it leaks protein. Most cataracts do not cause glaucoma. If your cataract does raise pressure, removing it with surgery stops the pressure increase.
Will my eye pressure go back to normal after cataract surgery?
In most cases, yes. If the cataract was causing the pressure increase, surgery removes the problem and pressure normalizes within days to weeks. Your eye doctor will monitor your pressure after surgery to confirm it has returned to normal.
How often should I have my eye pressure checked if I have a cataract?
If your cataract is being monitored rather than operated on, your pressure should be checked at every eye exam. This is typically once a year for stable cataracts, or more often if your doctor recommends it. If your pressure is already elevated, checks may be more frequent.
What is the difference between phacomorphic and phacolytic glaucoma?
Phacomorphic glaucoma happens when a swollen cataract physically blocks the drainage channel, usually causing sudden pressure increase and pain. Phacolytic glaucoma occurs when an old cataract leaks protein that clogs the drainage system, usually developing gradually over weeks or months. Both are treated with cataract surgery.
If I delay cataract surgery, am I more likely to develop high eye pressure?
Yes. The longer a cataract develops, the denser and more swollen it becomes, raising the risk that it will obstruct drainage or leak protein. This is one reason why your eye doctor may recommend surgery even if your vision is not severely affected.