This procedure can be used to correct both short sight (myopia) and long sight (hyperopia) that is too large to be safely and/or effectively corrected using laser surgery.

It is best suited to those patients aged over 50 years. This is because when the natural lens of the eye is removed all ability to adjust the focus of the eye is lost. This natural focus-ability of the eye is called "accommodation". It is slowly lost with ageing. This is why, for those who have good distance vision, near spectacles are usually required after mid 40's. When "Lens Exchange" is performed on those patients aged over 50 the loss of accommodation is of little consequence as it has already been lost through the ageing process anyway. The procedure may still be performed on younger persons but near vision spectacles will be a new requirement for such patients.

Lens Exchange involves removing the natural lens from the eye and replacing it with a tiny artificial plastic lens. This is called the intra-ocular lens implant, or IOL. The aim of the operation is to change the focus of the eye. The optical power of the lens implant is chosen so as to provide the desired post-operative focus for the eye.

The operation is usually performed under a local anaesthetic using a tiny incision in the eye, about 3 mms in length, and employs a technique called phacoemulsification. Lens Exchange surgery is technically very similar to modern cataract surgery and therefore involves tried and tested techniques.

Most eye surgeons will only operate on one eye at a time. This is the safest thing to do. If Lens Exchange is performed on both eyes at the same time there is a small risk that a complication could occur affecting both eyes; e.g. an infection. This could then lead to profound loss of vision in both eyes.

No. The natural lens of the eye must be physically removed and this can only be done surgically. The intra ocular lens implant is then inserted into the eye to replace the natural lens and to alter the focus of the eye. Sometimes following Lens Exchange (and cataract) surgery a membrane within the eye can be come opaque. This is called "posterior capsule opacification". Where necessary a laser can be used to treat this.

Nowadays most Lens Exchange operations are done using only a local anaesthetic and without an overnight stay in hospital. This simplifies the procedure and minimises the risk to the patient's general health. There are a number of different techniques for administering the local anaesthetic. The precise technique used will depend upon surgeon and patient preference.

The surgery should be pain free. The surgeon is as keen as the patient to achieve this because a relaxed patient is the key to good operating conditions. There are though some sensations. Some eye drops sting briefly as may the local anaesthetic injection if one is used. Some patients may be aware of a stretching sensation from the clip that holds the eyelids open during the operation. There may be an awareness of a light pressure from the fluids and instruments in the eye and the touch of the surgeon's hands around the eye.

A common practice is for a member of staff to hold the patient's hand during the operation. By squeezing this hand the patient can draw attention if any pain or distress occur. Any problems can then be addressed. The patient should avoid speaking during the operation unless given the OK to do so by the surgeon. This is because when speaking, the head and the eye may move and at the wrong moment this might upset the surgery

It is best to check will your eye unit about this. The pre-operative assessment is a good time to do this. Arrangements may vary from one eye unit to another and from one anaesthetist to another so it is not possible to give all encompassing advice. Some medication (e.g. regular blood pressure tablets) should be taken as usual, some medication (e.g. anticoagulants like Warfarin) may need to be stopped several days before surgery, and special arrangements may apply to some medication (e.g. those for diabetes).

No. If a local anaesthetic injection is used this will put the sight (vision) to sleep as well as removing feeling and paralysing eye movement. Even if only anaesthetic eye drops are used the bright light of the operating microscope will tend to bleach vision and the surgical manoeuvres are so close to the eye that there is little if any visual appreciation of what is happening. The other eye will be covered.

The aim of Lens Exchange surgery is to alter the focus of the eye. Special measurements of the eye are taken before the operation. Formulae are then used to calculate what power of intra-ocular lens implant to use in order to achieve the desired focus for the eye. In the large majority of patients the achieved new focus for the eye is close to that intended. The current consensus amongst eye specialists in the UK is that at least 85% of eyes should be within 1 dioptre of the intended focus. This does mean that for a minority of patients the focus of the eye after surgery is not quite as intended (though still usually much improved). For these patients spectacles, contact lenses or some additional surgical procedure may be required to get the focus "spot on".

One reason for missing the intended focus in some cases is that although the formulae used to calculate the intra-ocular lens power are well tried they are not perfect. This is because of biological variability. For example two eyes may appear the same and give identical measurements. However even if the same implant power is used the two eyes may not achieve the same focus after the operation.

There is a small risk in having any operation including Lens Exchange surgery. In the hands of an experienced surgeon, the risk of ending up with worse vision as a result of the surgery is very small; perhaps of the order of 1% or less. The risk of losing all vision or of requiring removal of the eye after the operation (e.g. because of an infection) is extremely remote; but it is not zero. The types of risk involved in having Lens Exchange surgery include:

Infection within the eye: Bleeding within the eye: Disturbance to the retina, e.g. a retinal detachment or a swelling of the centre of the retina called cystoid macular oedema.

Permanent clouding of the cornea: A long term increased pressure within the eye: A drooping of the upper eyelid.

These complications are rare. If they occur further surgery to the eye may be required. It should be emphasised that in the vast majority of cases Lens Exchange surgery is uneventful with excellent results. However this cannot be guaranteed.

In a small minority of cases technical difficulties can occur during Lens Exchange surgery. The delicate structures around the natural lens within the eye sometimes break. This can make it more difficult to remove the natural lens and/or safely insert the lens implant. For example the very thin membrane behind the natural lens may rip. This is called "posterior capsule rupture". This membrane separates the natural lens from the vitreous jelly which fills the main cavity of the eye. If this membrane breaks the vitreous jelly can move forward into the front part of the eye. Additional surgical steps are then necessary to remove this misplaced vitreous.

If these events are correctly dealt with the visual outcome is still favourable in most cases. Occasionally it is safer not to insert a lens implant when these complications occur, although this may be possible at a later date. Very rarely the natural lens may fall to the back of the eye during surgery. Referral to a vitreoretinal surgeon in order to remove it will then be necessary. Again it should be emphasised that in the vast majority of Lens Exchange surgery is uneventful with excellent results. However this cannot be guaranteed.

The intra ocular lens implant (referred to as the IOL by eye surgeons) is a clear plastic artificial lens inserted into the eye once the natural lens has been removed. The intra ocular lens implant replaces the natural lens of the eye; hence the term "Lens Exchange". Without a lens the eye would remain wildly out of focus and thick very strong spectacles or a contact lens would be needed to refocus the eye. Once inserted the intra ocular lens implant can be forgotten about by the patient. There are different types of lens implants and they can be made from a range of plastic materials.

A lifetime. The plastics from which the lenses are made have been subject to accelerated ageing tests. It is estimated that in the eye the lens materials will last in excess of 150 years before showing signs of significant degradation. There have been some rare reports of certain lens designs becoming prematurely opaque within the eye. These lenses have been withdrawn from the market.

If the surgery was routine and without complications it is extremely unlikely that the lens implant will move out of position.

In most cases no. The vast majority of Lens Exchange surgery is done on a day case basis. Occasionally it may be necessary to stay in hospital overnight following surgery, for example if a general anaesthetic is given towards the end of the day.

This is not essential but it can be helpful. If you wish to you may make arrangements directly yourself for a consultation with an eye specialist who performs Lens Exchange surgery. However your GP may be able to provide important background and medical information to the specialist. Also your GP may be able to help you decide which eye specialist you would like to see and advise you on how to go about doing this.

You should avoid any situation where you might be hit in the eye and you should not rub the eye. Usually the surgery is performed through a very small incision, often only 3mms in length. This means that the eye is very robust after the operation. The wound is extremely unlikely to give way.

It is OK to bend and do light physical activities almost immediately after the operation. If such activities cause the eye to throb then it is wise to stop and rest. Normal activities and past times can usually be fully resumed after about three weeks. However if a larger sutured incision has been used it may be 2 or 3 months before this can be done; always check with your surgeon if you are in doubt.

This depends. If you have driving standard vision and a normal field of vision in the fellow (non operated) eye then you may legally drive a private car on the day following the operation (applies to UK). However if you have been used to driving using two eyes it is wise not to drive until you have regained good and balanced vision in both eyes, or you have adapted and are confident to drive with only one eye.

The time taken for the eye to regain driving standard vision after the operation varies from one patient to another. Sometimes driving standard vision may be regained within days of the surgery but this cannot be guaranteed in advance. Sometimes new spectacles will be required in order to obtain driving standard vision. It is best to ask your surgeon and not to drive until he or she has stated that your vision has reached the required standard. Do not drive until the effects of the anaesthetic or any sedation have worn off.

This will vary from patient to patient. It depends on the nature of your work and the speed of recovery of the eye. Your own ophthalmic team will advise you.

There are though some general principles. Usually the surgery is performed through a very small incision without the need for sutures. With this surgery the eye usually takes about three weeks to fully settle. For sedentary occupations it may be acceptable to return to work after about a week. For work involving physical exertions 2 to 3 weeks may be preferable. If the job requires good quality well focused vision then the patient should wait until this is achieved which in some cases will not be until new spectacles have been obtained. If the surgery has involved a larger incision with sutures then the eye may take 2 to 3 months to fully settle. In these cases the return to work may be delayed somewhat.

When returning to work (and at other times too) avoid situations where you might be hit in the eye. Dry or dusty atmospheres may cause some irritation to the eye but are not directly harmful.

This will vary from patient to patient. Your ophthalmic team will be able to advise you.The type of surgery will affect how soon these activities can be resumed. Usually the surgery is performed using a small incision without the need for sutures. With this form of surgery the eye usually takes about three weeks to fully settle. If the surgery has involved a larger incision with sutures then the eye may take 2 to 3 months to fully settle. It may be wise to wait until the eye has fully healed before returning to swimming and sports although opinions do vary somewhat between surgeons. Contact sports and small ball games (e.g. tennis, squash, badminton) represent the greatest threat to the eye as they carry a risk of a direct blow to the eye.

The chlorine in swimming pools and the salt in the sea may irritate the eye a little more than normal in the first weeks after surgery but are unlikely to be directly harmful.

In most cases for 2 to 3 weeks, though occasionally it may need to be for longer than this.

There are no restrictions on flying after Lens Exchange surgery. It is quite safe to do so. The air conditioning within an aircraft may make the eye feel a little dry and irritable but this is not harmful. However do not fly away from post-operative supervision until your ophthalmic team are happy that the eye has sufficiently recovered from surgery.

The only situation where flying may be dangerous after eye surgery is when a bubble of gas has been placed within the eye. This is not done during Lens Exchange surgery. It is sometimes done for operations on the retina. Gas within the eye will expand at altitude.

Yes, most eye surgeons do require patients to wear an eye patch and/or a plastic shield over the eye after Lens Exchange surgery.

If a local anaesthetic has been used the patient may not be able to properly close the eye for a few hours following the surgery. A soft eye patch/pad is then used to keep the eyelids gently closed over the eye until the ability to blink has fully returned.

A plastic shield is also used to protect the eye from accidental pressure. This is usually kept in place over the eye until the day after surgery (i.e. through the night). If a small incision without sutures has been used many surgeons then dispense with the shield though some recommend continuing with it during sleep for several days. If a larger incision was used with sutures the wound is more vulnerable and it may be wise to continue to wear the shield during sleep/at night for a week or so.

Yes, probably to some degree. The usual aim with Lens Exchange is to alter the focus of the eye and reduce dependence on spectacles or contact lenses. However these may still be required after the operation in order to put the eye into optimal focus. For example if after the operation the eye is in focus for distance vision then reading spectacles may be needed.

After a Lens Exchange operation a thin membrane remains within the eye that separates the fluid filled space at the front of the eye from the jelly filled main cavity towards the back of the eye. This membrane is called the "posterior capsule". It is in fact the back layer of the natural lens of the eye which is purposely preserved (whenever possible) during surgery. It helps preserve the compartmentalisation of the eye and provides some support for the intra ocular lens implant. At the end of surgery this membrane is transparent. In some patients it may become hazy or opaque during the following months and years. This is called "posterior capsular opacification".

If this happens and this impairs vision the membrane can be treated using a laser. This is a quick simple painless outpatient procedure taking just a few minutes to perform. This treatment is called a "YAG laser posterior capsulotomy".

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