Cataract surgery: what happens before, during and after the operation?

"The doctor told me I have a cataract. Do I need the operation now? And what exactly will happen in the operating room?" This is one of the questions we hear most often. Cataract surgery is one of the most common and most successful operations in the world, but its success does not make it a "simple operation" that needs no decision or preparation. In this article we take you through the whole journey: when surgery is appropriate, how we prepare for it, what happens on the day, and what you can honestly expect afterwards.

What is a cataract?

Inside the eye, just behind the pupil, there is a clear natural lens that focuses light onto the retina, like the lens of a camera. With age, or with some conditions such as diabetes, this lens gradually loses its clarity and becomes cloudy. This clouding is a cataract.

It is like looking through a window pane that is gradually misting up: vision becomes hazy, colors look faded, and glare from car headlights at night gets worse. Some patients also notice their glasses prescription changing again and again.

There is still no medicine or eye drop proven to treat cataract. The only effective treatment is surgery: the cloudy lens is removed and a clear artificial lens is implanted in its place, where it stays permanently.

When is surgery appropriate?

There is no single number on the eye chart that sets the right time for everyone. The official British guideline clearly recommends not basing the decision on visual acuity alone (National Institute for Health and Care Excellence, 2017).

The decision depends mainly on how much the cataract affects your life: reading, driving (especially at night), work, and moving around safely. Sometimes there is an additional medical reason, such as the doctor needing a clear view of the retina to follow another disease like diabetic retinopathy.

A common belief is that a cataract must "ripen" before surgery. This is not true. Timing depends on its effect on your life and the state of your eye, not on "ripeness" (National Institute for Health and Care Excellence, 2017). That is why the decision is shared: the doctor explains the condition, the patient describes how it affects daily life, and they decide together (European Society of Cataract and Refractive Surgeons, 2024).

Before surgery: three important things

First: precise measurements to choose the lens power

We measure the length of the eye and the curvature of the cornea with precise instruments to calculate the right lens power. If you have ever had LASIK or any other vision-correction surgery, tell your doctor, because it changes how the calculation is done (National Institute for Health and Care Excellence, 2017).

Second: examining the retina and the rest of the eye

Cataract is not always the only reason for poor vision. If there is another eye disease, such as diabetic retinopathy, a membrane on the macula, or glaucoma, vision may improve less than expected after surgery. In a large British database, about 95% of patients with no other eye disease reached a good level of vision after surgery, while results were lower in those with other eye conditions (Day et al., 2015).

That is why the retina needs a careful examination before surgery, so that expectations are realistic from the start.

Third: choosing the type of lens

There are different types of implanted lens. A monofocal lens is the most widely used; it gives clear vision at one distance (usually far), and the patient usually needs reading glasses afterwards. Multifocal lenses reduce dependence on reading glasses for many patients, but they increase the chance of seeing halos and glare around lights (de Silva et al., 2016), and they may not suit some retinal diseases. If the patient has significant corneal astigmatism, a toric lens improves vision without glasses, without increasing complications (Kessel et al., 2016). We compare the lens types in detail in our article on choosing an intraocular lens.

The choice is a shared discussion between you and your doctor about your lifestyle, your need for glasses, and the health of your retina (National Institute for Health and Care Excellence, 2017; European Society of Cataract and Refractive Surgeons, 2024).

The day of surgery

The operation is usually done under local anesthesia, with drops or an injection next to the eye; the patient is awake but feels no pain. A very small opening is made at the edge of the cornea, the capsule surrounding the lens is opened, and the cloudy lens is broken up with ultrasound and removed. This is phacoemulsification ("phaco"). The artificial lens is then implanted inside the same capsule.

In many centers the operation ends with an antibiotic placed inside the eye. This practice is recommended by the European Society of Cataract and Refractive Surgeons (European Society of Cataract and Refractive Surgeons, 2024), because a large European study found that the risk of infection was about five times higher when it was not used (ESCRS Endophthalmitis Study Group, 2007).

What about "laser cataract surgery" (femtosecond)?

Many patients ask about it, assuming that newer means better. But scientific reviews and large trials did not find clearly better results than conventional phaco, either in vision or in complications, while the cost is higher (Schweitzer et al., 2020; Narayan et al., 2023).

After surgery

Drops: you will use anti-inflammatory drops for several weeks as your doctor instructs. Guidelines recommend them to prevent inflammation and to prevent swelling of the macula after surgery (National Institute for Health and Care Excellence, 2017). In a European trial, combining two types of anti-inflammatory drops was best at reducing this swelling in patients without diabetes (Wielders et al., 2018a).

Vision: usually improves over days to weeks, and you may need new glasses once the eye has settled.

The second eye: its timing is decided by the same criteria as the first eye, that is, according to how much the cataract affects you (National Institute for Health and Care Excellence, 2017).

The risks: frankly, and at their real size

Cataract surgery is among the most successful and safest operations, but it is still surgery, and it has risks that patients should know:

A tear in the back of the lens capsule during surgery (posterior capsule rupture): this happened in about 1–2% of operations in large European and British registries (Day et al., 2015; Segers et al., 2022). When it happens, the risk of retinal detachment and infection after surgery increases (Day et al., 2015). Diabetic retinopathy was one of the factors most strongly linked to this tear in the European registry (Segers et al., 2022).

Swelling of the macula after surgery: this occurs in about 1 in 85 patients without risk factors, and is much more common in people with diabetes, retinopathy, a membrane on the macula, or a previous retinal vein occlusion (Chu et al., 2016). It usually responds to treatment.

Infection inside the eye: rare but serious, which is why sterility and the antibiotic matter so much, and why patients should know the warning signs (ESCRS Endophthalmitis Study Group, 2007).

Retinal detachment later on: in a large American registry, it happened within the first year in about 1 in 500 patients (Morano et al., 2023). So everyone who has had the operation should know the symptoms of retinal detachment: flashes, new floaters, and a shadow.

Clouding of the back of the capsule (posterior capsule opacification): months or years later, the capsule that holds the artificial lens may become cloudy and vision becomes hazy again. Some patients call this "the cataract coming back," but it is not. It is treated with a laser in the clinic in a few minutes, without another operation (Brézin et al., 2023).

These figures come from large external registries and studies, not from the results of any particular clinic.

If you have diabetes or a retinal disease

Here the operation needs extra planning. The chance of swelling of the macula after surgery is higher (Chu et al., 2016), and diabetic retinopathy itself may progress in the year after surgery (Lee et al., 2025). So it is better to stabilize the retina before surgery as far as possible and to plan close follow-up afterwards. The surgeon may use an additional anti-inflammatory treatment for some patients with diabetes: in a European trial, a steroid injection next to the eye reduced the thickness of the macula (Wielders et al., 2018b). We cover this in detail in our article on cataract surgery in diabetes.

A patient with a retinal problem benefits from having both parts, the cataract and the retina, assessed together, so that there is one coordinated treatment plan.

Questions patients often ask

Can a cataract be treated with drops?

There is no proven medical treatment. Surgery is the treatment.

Does a cataract have to "ripen" before surgery?

No. The timing depends on its effect on your life and the state of your eye (National Institute for Health and Care Excellence, 2017).

Will I need glasses after surgery?

That depends on the type of lens you choose. With a monofocal lens, most patients need reading glasses.

Can both eyes be operated on the same day?

This is done in some health systems under specific conditions (National Institute for Health and Care Excellence, 2017), and your doctor will discuss it with you according to your case. In our clinic, however, we do not favor this approach at all, except in rare exceptions.

Can the cataract come back after surgery?

The cloudy lens cannot come back because it has been removed. But the back of the capsule can become cloudy, and this is treated with a laser.

Summary

Cataract surgery is one of the most successful operations in medicine, but its best results come from a well-considered decision: the right timing for the patient's life, a careful examination of the retina before surgery, a clear choice of lens, and good follow-up afterwards. No single approach suits every patient, and we discuss with each patient the options that suit their case and what they can honestly expect.

This information is for health education and does not replace a medical examination.