What is a Cataract?

A cataract is a clouding of the natural lens of the eye. The natural lens is positioned just behind the pupil. In childhood and early adulthood it can change shape in order allow the focus to change from the distance to near, for instance to allow you to read.

However as one gets older it becomes more rigid and reading glasses may be required.

Eventually it may become cloudy. The most common reason for this is simply age. The lens grows slowly throughout life. Eventually it becomes too big to be kept healthy and starts to cloud over.

Other reasons that may result in cataract are diabetes, a family history of early cataract, ocular inflammation (“uveitis”) or injury.

How is a cataract treated?

Modern treatment of a cataract is to remove it through two small incisions in the eye. These incisions are approximately 2.5mm in length or smaller. This allows the operation to be performed without the need for any stitches.

When the cataract has been removed it needs to be replaced with a plastic lens, referred to as an intraocular lens or “IOL”. This is rolled up and inserted through the small incision which then unrolls inside the eye. It is a bit like putting a “Ship in a Bottle”.

You can see a video of this at https://www.youtube.com/watch?v=T2TuT1wM9h8

Most operations are done under local anaesthetic. In practice this just requires drops and works very well. However it is possible to give sedation or even a general anaesthetic if required.

What kind of lens do I need?

Essentially every patient needs to have a lens inserted. There are three types of lens.

Monofocal Lens

This is the standard lens used in the large majority of patients. Before your operation a test will be done to determine how strong the lens needs to be.

As a general rule most patients decide to be focussed in the distance when not wearing their glasses (e.g. when watching television, driving, walking about). But some patients who have always been short sighted may elect to remain able to read without glasses, and these patients are happy to wear them for distance. It is a personal choice.

On rare occasions there may be an issue with balance between the glasses requirement of the two eyes, and this can make the choice of lens difficult.  If so this will be discussed with you.

Toric Lens

Some patients have astigmatism. This means that the eye is a bit rugby ball shaped and that the patient has to wear glasses that correct for this, as well as correcting for any long or short sight. Mild astigmatism will have little effect on the vision but if there is a lot of astigmatism present then the patient should consider a Toric lens. Toric lenses are more expensive than monofocal because each has to be manufactured to order for each patient. But they do allow patients with significant astigmatism to see a lot better without glasses then they would with just a monofocal lens.

Multifocal lens

These are lens that are designed to allow the patient to both read and see in the distance without glasses.

These lenses indubitably allow more people to see at both near and distance without glasses than monofocal lenses do. However it should be borne in mind that these lenses can result in some loss of contrast (e.g. things are not quite so black and white as they might have been) and these lenses produce more problems with glare, such as when driving at night.

What problems could arise with my Cataract Surgery?

Serious complications of cataract surgery are now very rare, but instances still occur.

There could be a problem during the operation. For example, natural lens capsule could become ruptured. This event increases the risk of infection or retinal detachment and which can result in visual loss. In addition if posterior capsule rupture (PCR) happens it may not be possible to insert a lens and a second operation may be required.

As with any operation there could be complications, infection is regarded as the most important. However infection rates have come down a lot in recent years from about 2 per thousand operations at the beginning of the century to well under 1 per thousand now. Infections can be treated but it is possible for an infection to result in loss of sight.

Lesser problems


Most eyes settle down quickly within a few days of the operation. But sometimes the eye is uncomfortable for a bit longer but it still settles down.

Cystoid oedema (CMO)

This is a swelling of the central retina following the operation. The central vision may become blurred for a period, usually a few weeks but sometimes several months. The exact mechanism that causes CMO is not well understood but as a rule it essentially always resolves and good eyesight results.

The sight without glasses is not as good as expected but is fine with glasses

The main reason for this is that the IOL is not the right strength. The test for the choice of implant (IOL) is generally very accurate but nevertheless this is not a perfect science. So the surgery might leave you slightly more long or short sighted than intended.

How long will I be in the hospital for my operation?

Patients are free to return home shortly after the operation. At most you will be in the hospital for a few hours. However the operation itself is very short, generally less than 10 minutes from the start to finish of the procedure.

Patients who are having a local anaesthetic (including those having oral sedation) can eat and drink normally. Before the operation dilating drops will be put in your eye. After the operation you will receive an explanation from the surgeon and nurses of what to expect during the recovery period.

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