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Cataract, Cataract Surgery & Refractive Lens Exchange including PRELEX (PREsbyopic Lens EXchange).

Within the eye there is a lens. This is normally transparent like window glass. When it becomes hazy like bathroom window glass, it is called a cataract. When the vision is affected to such an extent that normal daily activities are difficult, or when the visual disturbance impacts on quality of life, then surgery should be considered. It is no longer necessary to wait for the cataract to become "ripe" (a term from the 1950s) or for all vision to be lost before undertaking the cataract operation.

Cataract surgery is generally so successful that it has become the commonest operation performed in virtually all developed countries. However, many studies have shown that the very low complication rates are lowest when an experienced surgeon carries out the procedure.

The cataract operation aims to improve your vision by removing the misty lens and replacing it with an implant or intraocular lens (IOL). This is done using an ultrasonic probe through a small incision in the cornea or clear window of the eye. The operation aims to leave behind the bag, or capsule, of the cataract to act as a support for the intraocular lens. The intraocular lens does not require cleaning or indeed wear out, and the modern foldable intraocular lenses enable the operation to be performed through a much smaller wound, meaning few restrictions for you after the operation. Most patients can resume normal activities the next day.

The IOL can be one of two classes: Monofocal or Multifocal. Monofocal IOLs have a single focal point, i.e. are in focus on objects at only one distance from the eye. Surgery with monofocal IOLs is usually targeted on good vision for distance without glasses, meaning spectacles for reading and near-vision tasks will be required.

Multifocal IOLs come in three versions: bifocal, trifocal and extended depth of vision (EDOF). These IOLs have the big advantage of reducing the need for spectacles and indeed many patients are spectacle-independent. Although it needs to be discussed with you in detail, bifocal IOLs are good for reading and distance, but not so good for intermediate, and trifocals are good at intermediate too, but both these IOL classes work by producing "simultaneous vision" meaning that some patients are aware of a ghost image, especially at night. Almost all patients learn to ignore the ghost image over a 6 month period by a process called "neuro-adaptation". In contrast, the EDOF lenses are less likely to cause ghost images and are good for distance and intermediate, but perhaps not quite as good for near especially very small tasks such as sewing when spectacles are likely to be required. However, there is no doubt that for most people who dislike spectacles, multifocal IOLs have a lot to offer.

After surgery, vision may still be slightly blurry in the first few days after the operation - the eye will be inflamed and need time to settle before the full vision is returned. A change in glasses may be needed after the operation, before the full benefits are realised. Old glasses may be worn after the operation if this helps the sight; they will not do the eye any harm. Sunglasses may be useful if lights are found to be very dazzling - do what keeps comfortable and allows you to see best. Drugs given as eye drops will be needed after the operation, usually for 4 weeks. These are important to minimise the risk of infection and to help the eye inflammation settle quickly - please use them regularly as instructed. In some cases they may need to be continued longer, but the consultant will provide instructions to this effect. The eye should not be painful after the operation - a scratchy feeling or a mild ache is quite usual and should settle with painkillers such as paracetamol. Should the eye become very painful, and especially if the vision from the eye worsens then you should contact the practice immediately.

There are very few restrictions required after this type of operation because the wound is so small. Please do NOT rub the eye as this will be painful and may do damage although this is highly unlikely. Try to avoid anything too strenuous for about a fortnight after the operation and avoid swimming whilst using the drops. Reading and television are not a problem and neither is bending, but please avoid spring-cleaning and heavy gardening for about a month. If you have a particular worry about a special activity, please ask your consultant.

The world will be a brighter place after the operation but may still be a bit fuzzy until new glasses are prescribed if needed. In a proportion of patients the bag that held the cataract can thicken in the year or eighteen months following the surgery. This can require a laser procedure to divide the thickened bag; this is performed as an outpatient. There are other complications of cataract surgery - these are rare and the operation carries a 95+% success rate. Should you have questions or worries please ask your consultant.

Spectacles After Cataract Surgery & Refractive Lens Exchange / PRELEX

A refractive lens exchange is essentially a cataract operation done for patients who dislike spectacles. In general, patients who are over 45 years of age may be suitable. The IOL implanted is usually targeted on good vision for distance without glasses, meaning spectacles for reading and near-vision tasks will be required unless a type of multifocal IOL is used. Surgery using multifocal IOLs for refractive lens exchange was first described by Professor Claoué at ESCRS in 1997, and has become the "gold standard" for lens-based presbyopia surgery. Now that toric multifocal IOLs are available, most eyes are suitable for this surgery. However, a consultation is essential to determine suitability, and to make sure that your expectations are likely to be met.

Refractive Errors & Their Surgical Treatment

There are four sorts of refractive error (problems with focusing.) Some of these can be combined. The four sorts of refractive error are myopia or short sight; hyperopia (hypermetropia) or long sight; astigmatism and presbyopia. Astigmatism and presbyopia treatment can be combined with either myopia or hyperopia.

Normal Focusing

In the perfect eye distant objects are naturally in focus on the retina at the back of the eye and are seen clearly; this is called emmetropia. In youth, as the object comes closer, the eye is able to change its focus by a process called accommodation, which keeps the object in focus. This is sometimes called "Eumetropia".

Myopia or Short Sight

If an eye is short sighted, it is able to see things in focus at short distances. Objects in the distance are blurred because the focusing power of the eye is incorrect for the length of the eyeball. The eye is too long for the focusing power of the front of the eye. Whilst eyes that are short sighted can achieve clear vision with spectacles or contact lenses in many cases this can also be treated by a variety of laser and other surgical techniques. Up to the age of 40, Femto-LASIK is the preferred technique for myopia up to a maximum of 10 dioptres if the cornea is not too thin, but between 40 and 45 satisfaction rates fall, and it is not recommended after 45 years of age. Lens-based surgery is also possible.

Hyperopia or Long Sight

With a long-sighted eye, it is usually possible to see things in focus that are a long distance away but close work is either difficult and tiring or impossible. This condition exists because of a disparity between the focusing power of the front of the eye and the length of the eyeball. In this condition the eyeball is too short for the focusing power of the eye but to some extent the natural process of accommodation is able to compensate and many such patients are able to maintain good vision whilst young adults. However, the ability to accommodate decreases with age and many of these patients become spectacle dependent in mid-life. Whilst hyperopia can be treated with contact lenses or spectacles, surgical techniques now exist to treat many cases, and hypermetropic individuals tend to be the most grateful group after lens-based surgery. Femto-LASIK can correct hypermetropia up to about +3.5 dioptres.


Almost all eyes have a small amount of astigmatism. It is not a disease, but an optical state of the eye where the front of the eye, instead of being equally curved in all directions (such as the side of an orange or a football) is more curved in one direction than the other (such as the side of a lemon or a rugby ball). If significant astigmatism exists, then objects will appear blurred at all distances unless the astigmatism is corrected by spectacles, contact lenses or surgery. Surgery for astigmatism is usually combined with surgery for either myopia or hyperopia.


It is well known that people who have enjoyed good vision for distance will require reading glasses sometime after the age of 45. This is due to presbyopia, which is a normal phenomenon. It is caused by the progressive loss of the ability of accommodate i.e. change the focus of the eye, and is a normal developmental phenomenon. Whilst presbyopia has been treated with spectacles or special contact lenses, we now have surgical techniques available which will treat presbyopia in certain selected cases. See PRELEX above.

Cataract Cataract Surgery