Cataract – before the operation

It is important to make sure that all your questions about cataract surgery are answered before you come in for the operation, so that on the day you are in a relaxed and confident frame of mind. This section discusses some of the points which are useful to know about cataract surgery. There are some important medical points that can influence the success of a cataract operation and these are mentioned below.

Medications

Any medication which thins the blood can lead to more bruising around the eye after surgery. This is why it is important to check the blood levels of warfarin before an operation. Other medications can also increase the risk of bruising or bleeding include aspirin, ibuprofen, brufen, indomethacin, clopidrogrel. Some over the counter supplements such as ginkgo biloba can also lead to an increased risk of bruising or bleeding. It may be necessary to stop these medications before surgery and Mr McLean will discuss this with you.

Muscle relaxants, such as tamulosin, alfuzosin, doxazosin and indoramin, which are used to treat benign prostatic hyperplasia, can make cataract surgery more complicated. The iris, the coloured part of the eye, normally remains still during cataract surgery, but after using tamulosin (or similar alpha blocker drugs) the iris can behave in a very erratic way, becoming mobile and unpredictable. This can lead to an increased risk of complications during surgery. Knowing a patient is on tamulosin before surgery helps to prepare for unexpected iris movement during surgery.

Previous eye treatments or conditions

It is becoming more common to have refractive laser surgery, to try to reduce the need for glasses. This becomes a very important factor in cataract surgery, as the calculations used to predict the strength of the new implant lens needed for any one person can be severely affected by previous laser treatment. Without adjusting the formula used to predict the best lens strength, to take into account previous laser refractive surgery, then the wrong lens might be used. As a consequence, it is very import to mention any previous refractive treatments before undergoing cataract surgery, even if the treatments were many years ago.

There are several eye conditions that can influence cataract surgery, either by making the operation harder and more prone to complications, or which can affect the final level of vision achieved after surgery. If you have any of these conditions, Mr McLean will discuss the implications with you.

Eye measurements before the operation

An important step before cataract surgery is the measurement of the eyes. Once the length of an eye is measured and the curvature of the cornea then it is possible to calculate the strength of the new lens that is to be used during cataract surgery. There are different machines available to perform these measurements, but the IOL Master is the one most frequently used as it produces highly accurate, reproducible results. The measurements take a few minutes to capture and involve no discomfort.

IOL Master Biometry

The IOL Master biometry machine taking measurements

Contact lenses

If you normally wear contact lenses then it is important to leave them out before measuring the eye with the IOL Master. This is because the contact lenses can change the curvature of the cornea, and as this plays a vital role in the implant lens calculations, any inaccuracies can affect the final outcome of the cataract surgery. Therefore, contact lenses should be removed for between 1-3 weeks before calculations are made, depending on the type of contact lens used. Mr McLean will discuss this with you to advise you how long to leave the lenses out for. Usually, soft contact lenses are left out for one week and rigid gas permeable or standard hard lenses are left out for three weeks before the measurements are made.

Choice of intraocular lens

Recently there have been significant advances in the design of intraocular lenses used in cataract surgery. This means that there is more choice and so it is important to be aware of the options available. The lens manufacturers have divided lenses into groups ‘standard’ and ‘premium’.

The standard lens is an extremely high quality lens which is monofocal. This means that the light coming through the lens will be focused onto one point. Most patients are keen to have good distance vision after cataract surgery and so this means that near objects will be blurry without glasses. Rarely, patients who have been very short sighted and spend a lot of time reading without glasses, want to be able to read without glasses after their cataract operation. This means that after surgery they will need to use glasses for distance vision. In summary, the standard lens is a high quality lens which the vast majority of patients opt for, and requires the use of glasses afterwards, usually for reading. As many patients already wear glasses, this is not a problem.

Premium intraocular lenses are more expensive as they are designed to do more than a standard, monofocal lens. There are three categories of premium lens which overlap. There are toric lenses, which correct astigmatism. If there is a lot of astigmatism, a standard monofocal lens will not give sharp vision alone, and so either glasses are necessary (for distance and close vision) or the need for distance glasses can be reduced with a toric intraocular lens.

Next there are lenses which help to improve both the distance and near vision. These fall into two categories, multifocal and accommodating lenses. The multifocal lenses (such as the Restor lens) are a combination of lenses within one lens which can give both near and distant vision at the same time. The brain requires a little time to adjust to this, but after a few weeks it is possible to see close and distant objects in focus. The accommodating lenses (such as the Crystalens AO) are able to flex and change shape, thereby altering the focusing power of the lens. They can provide near and distance vision as long as the lens is able to flex within the eye. Lastly, there are lenses which combine toric correction with a multifocal lens.

It is important to remember that with any lens implant, although the calculations predicting which lens is best for a patient are very accurate, there are other factors within the eye which can affect the positioning of the lens, and hence the focusing of the eye after surgery. In some cases, this can mean that if the focusing is unexpectedly blurry after surgery, further treatment may be necessary to try to reduce the dependence on glasses and this can include replacing the lens for one of a different strength or laser surgery.

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Surrey Eye Surgeons

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