Cataract Surgery · Patient & Surgeon Series
The ache the night
after surgery is often
pressure, not pain.
A short-lived rise in eye pressure is one of the most common events in the first day after cataract surgery. Most of the time it is mild and settles on its own. In an eye with glaucoma, or when the spike is high, it matters. Here is why it happens, who is at risk, what it feels like, and how surgeons prevent and treat it.
of the early peak
normal range
response shows up
Section 01 — What Is Happening
The drain is fine.
Something is
sitting in it.
The front of the eye is filled with aqueous humour, a clear fluid that is made continuously behind the iris and drains out through the trabecular meshwork, a fine filter in the angle where the iris meets the cornea. Eye pressure (intraocular pressure, or IOP) is the balance between how fast fluid is made and how easily it drains.
Cataract surgery changes that balance for a few hours. Material left in the eye at the end of the operation — mostly traces of the viscoelastic gel (OVD) used to protect the cornea and hold the chamber open, plus inflammatory cells, protein, pigment and tiny lens fragments — flows towards the meshwork and partly blocks it. Fluid production carries on, drainage slows, and pressure climbs. As the debris washes through and the inflammation settles, the pressure comes back down, usually within a day.
A raised eye pressure after cataract surgery is usually a temporary outflow problem, not a new disease. Retained viscoelastic, inflammatory debris and pigment partly clog the trabecular meshwork for the first several hours, so pressure rises and typically peaks around 4 to 6 hours after surgery before settling within 24 hours. A healthy optic nerve tolerates a short, moderate spike well. Eyes with glaucoma, pseudoexfoliation, a high myopic disc or a recent vascular event tolerate it poorly, which is why surgeons check pressure early in those patients and often give a pressure-lowering drop or intracameral miotic at the end of the case. A later rise, weeks after surgery, is a different problem: usually a reaction to steroid drops.
Section 02 — Interactive
Leave more gel behind,
and watch the angle fill.
Move the slider to change how much viscoelastic is left in the anterior chamber at the end of surgery. Particles drift towards the drainage angle, and the readout shows where an illustrative pressure would land relative to the thresholds clinicians commonly use.
The relationship in real eyes is not linear and not the same for every gel. Long-chain, high-molecular-weight cohesive OVDs tend to leave the eye as a single mass when aspirated properly, but any fragment left behind is very effective at blocking outflow. Dispersive OVDs coat tissue and are harder to remove completely, so small amounts are more often left behind, although each fragment is less obstructive. Comparative studies of different viscoelastics since the late 1980s have repeatedly found that the size of the early spike depends on both the agent and how thoroughly it is removed.
Section 03 — Timing
Hours, weeks, or
months: the clock
tells you the cause.
When the pressure rises is the single most useful clue to why. Surgeons sort post-operative pressure rises by timing first, because the treatment for each is different.
| When | Most likely cause | Usual course |
|---|---|---|
| First 24 hours | Retained OVD, inflammatory debris, pigment | Peaks at roughly 4–6 hours, settles within a day; treated with drops or chamber release if high |
| Day 1–7 | Persistent inflammation, blood in the chamber (hyphaema), retained lens fragment, pupillary block | Needs examination to identify the cause; a retained fragment may need removal |
| Week 2–6 | Steroid response to anti-inflammatory drops | Reverses after switching to a lower-potency steroid or an NSAID, or stopping |
| Months later | Underlying glaucoma progression, pigment dispersion from a misplaced IOL, chronic inflammation | Managed as glaucoma; an IOL rubbing the iris may need repositioning |
The steroid response deserves its own mention because it catches patients off guard: the eye felt fine at the one-day visit, and the pressure is found high at the two- or four-week check. Classic studies in the 1960s by Armaly and Becker showed that people vary widely in how their pressure reacts to topical corticosteroids — roughly a third of the general population show a moderate rise, and a small minority a marked one, with higher rates in people who already have glaucoma or a family history of it. This is one reason the follow-up visits after cataract surgery are worth keeping even when vision is already good.
Section 04 — Who Is at Risk
The same spike
means different things
in different eyes.
A healthy optic nerve can absorb a few hours at a moderately raised pressure without harm. A nerve that has already lost fibres to glaucoma has less reserve, and a high spike can cause further damage or, rarely, a vascular event. Risk sits partly in the eye and partly in the surgery.
Section 05 — Symptoms
What a pressure spike
feels like.
Normal recovery after cataract surgery involves a gritty or scratchy feeling, watering and blurry vision that improves over the first days. A pressure spike tends to feel different, and the difference is worth knowing.
A high pressure usually causes a deep, dull ache in or around the eye, often spreading to the brow or temple, that comes on several hours after surgery — frequently in the evening or overnight. Vision may become foggier rather than clearer, and lights can show coloured haloes because a high pressure pushes fluid into the cornea and makes it hazy. Very high pressures can cause nausea or vomiting. Mild rises often cause no symptoms at all, which is why surgeons measure rather than wait for complaints in higher-risk eyes.
Section 06 — Prevention & Treatment
Prevent it in theatre,
treat it by cause.
Most of the work happens before the patient leaves the operating room. Thorough OVD removal is the foundation. In higher-risk eyes surgeons add a pressure-lowering step at the end of the case.
At the end of surgery. Intracameral miotics such as carbachol and acetylcholine constrict the pupil, and carbachol in particular has been shown in randomised studies to blunt the early post-operative pressure rise, with an effect lasting through the first day. Many surgeons also instil a topical pressure-lowering drop — an alpha-agonist such as brimonidine or apraclonidine, or a beta-blocker such as timolol — and some prescribe oral acetazolamide for patients with advanced glaucoma.
If the pressure is high at review. Topical drops are the first step. When the pressure is very high, the surgeon can release a small amount of aqueous through the side-port incision at the slit lamp (often called “burping” the wound), which lowers pressure within seconds and is followed by drops. Steroid-related rises are handled by switching the anti-inflammatory regimen. Mechanical causes — a retained fragment, pupillary block, blood — are treated directly, sometimes with a laser iridotomy or a short return to theatre.
| Approach | How it works | Typical use |
|---|---|---|
| Complete OVD aspiration | Removes the main source of outflow obstruction | Every case |
| Intracameral carbachol | Miosis plus increased outflow; reduces the early spike | End of case, especially glaucoma or PXF eyes |
| Topical alpha-agonist / beta-blocker | Reduces aqueous production; some increase outflow | End of case or at review if pressure is raised |
| Oral carbonic anhydrase inhibitor | Systemic reduction in aqueous production | Selected high-risk or very high pressure; not suitable for everyone |
| Side-port release (“burping”) | Lets a little aqueous out to drop pressure at once | Very high early pressure with a well-formed chamber |
Section 07 — The Agaaz Range
The consumables that
sit on both sides
of this problem.
Agaaz Ophthalmics supplies viscoelastics and intracameral solutions for cataract surgery. The pressure story above runs straight through two of them: the OVD that has to be removed well, and the miotic used to blunt the spike when it is not enough. No consumable eliminates post-operative pressure rise; technique and patient selection matter as much as the product.
For the rheology behind OVD removal, see the cohesive vs dispersive OVD guide. View the complete portfolio →
Section 08 — FAQ
Frequently asked questions
about pressure after cataract surgery.
A mild, temporary rise in eye pressure in the first day after cataract surgery is common and usually settles on its own within about 24 hours. It is mainly caused by traces of viscoelastic gel, inflammatory debris and pigment partly blocking the eye's drainage meshwork. A healthy optic nerve tolerates a short, moderate rise well. A high spike, or any rise in an eye with glaucoma, is treated promptly.
The early rise typically peaks around 4 to 6 hours after surgery, which is why symptoms often appear in the evening or overnight, and it usually returns towards normal within a day. A separate, delayed rise can appear two to six weeks later in people whose pressure reacts to steroid eye drops.
A significant rise usually causes a deep, dull ache in or around the eye that may spread to the brow or temple, foggier rather than clearer vision, and sometimes coloured haloes around lights. Very high pressure can cause nausea or vomiting. Mild rises often cause no symptoms, so surgeons measure pressure in higher-risk eyes rather than waiting for complaints.
Yes. Some people are steroid responders, meaning their eye pressure rises when they use corticosteroid drops, usually two to six weeks into treatment. It is more common in people with glaucoma, a family history of glaucoma or high myopia. The rise reverses when the surgeon switches to a lower-potency steroid or a non-steroidal drop, or stops the steroid.
Treatment depends on the cause. Most early rises respond to pressure-lowering eye drops such as an alpha-agonist or beta-blocker, sometimes with an oral medicine. A very high early pressure can be lowered at once by releasing a small amount of fluid through the side-port incision at the slit lamp. Steroid-related rises are managed by changing the drops, and mechanical causes such as a retained lens fragment are treated directly.
In a healthy eye a short, moderate spike rarely causes lasting harm. In an eye with advanced glaucoma, where the optic nerve has little reserve, a high spike can cause further nerve damage, and very high pressures carry a small risk of vascular events. That is why patients with glaucoma or pseudoexfoliation often have their pressure checked within hours of surgery and are given preventive drops.
The foundation is thorough removal of the viscoelastic gel at the end of the operation, including the gel trapped behind the lens implant. In higher-risk eyes surgeons commonly add an intracameral miotic such as carbachol, which has been shown to reduce the early pressure rise, and a topical pressure-lowering drop at the end of the case.
References & Evidence Base
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