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Refractive surgery of the Lens and correction of presbyopia

People with refractive errors (see children section for refractive errors) can have surgery to correct this. The most common procedure for this involves reshaping the cornea using a laser and is known as LASIK or LASEK. This type of surgery is better covered elsewhere.

Refractive errors can also be treated by removing the lens of the eye and replacing it with an appropriately powered implant that corrects the original refractive error. This is most commonly done as part of an operation for cataract.

Short-sighted eyes are optically too strong. The lens is replaced with an implant of reduced power. The eye ends up less powerful and therefore less short-sighted.
 A longsighted eye is optically too weak. Replacing the lens with an optically more powerful implant increases the power of the eye and improves the long sight. Implants can also correct for astigmatism. This is usually done using traditional implants that have a fixed (none changing) focus, monofocal implants.

Additionally there are implants that can change focus. They are used for people whose lenses have lost the ability to change focus and require reading glasses (see presbyopia).

A multifocal implant

A multifocal implant

There are two type of implant that can do this. Multifocal implants are optically stronger in their centre. When you look close up, your pupil naturally becomes smaller. With a multifocal implant in the eye when looking close up you use the central stronger focusing area of the implant as your pupil constricts. In this way you can read without glasses.
Accommodating implants work differently. They respond to the internal muscles of the eye used when looking close up. In effect they change shape and become stronger, a bit like how the natural lens works in younger people.

Either implant has advantages and disadvantages. Multifocal implants inevitably produce glare because of the optical etchings used to make the central part of the implant stronger. Most people adapt to the glare (also described as haloes and/or starburst). Not everyone can adapt to this, for example people who drive long An accommodating implantdistances especially at night can have problems with these implants. Accommodating implants do not produce glare and would seem the better option. However they do not have as great an effect in increasing the power of the eye in close up, so people with these implants are more reliant on reading glasses.
For the best effect both eyes would need to have some form of presbyopia correcting implant. Most surgeons recommend using the same type of implant in both eyes, though other surgeons do mix and match. Each patient has to be carefully counselled.

Another type of implant can be used to treat astigmatism but these are usually used in operations for cataract surgery. Those without cataracts would normally have corneal surgery to correct this.

An accommodating implant

One other option is to use monofocal implants and induce a state known as monovision. Here one eye is rendered short-sighted allowing clear near vision, whilst the other is made neutral allowing clear vision in the distance. One eye therefore is used for the distance with the other being used for reading. This gets round the problems associated with the presbyopia correcting implants. Unfortunately not everyone can cope with monovision. Before committing to this most surgeons would temporarily induce this state with contact lenses to ensure that person was comfortable with it. Indeed most people requesting monovision have been contact lens wearers anyway and used monovision for many years.

The above options are available to people about to undergo cataract surgery.
It is possible to replace a clear healthy lens with these implants to treat refractive errors and/or presbyopia. This is called clear lens extraction. It’s basically a cataract operation on an eye that does not have a cataract. In most cases both eyes will require surgery.  Like cataract surgery there is a small risk of serious complications that can blind the eye. Potentially an eye that, using glasses, could see perfectly normally is being put at an albeit small risk of blindness.

The decision to go ahead with clear lens extraction to treat refractive errors or presbyopia clearly needs a great deal of thought beforehand.
Laser surgery on the cornea can also treat presbyopia but has the same disadvantages regarding glare and haloes that multifocal implants have.

Refractive surgery either in the form of  corneal laser surgery or clear lens extraction is not available on the NHS.

General eye problems

Adult Squint
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AMD
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Presbyopia and normal ageing of the eye
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Cataract
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Cataract FAQ's
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Refractive surgery of the lens and correction of presbyopia
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Dry eye
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Glaucoma
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Retinal Vein Occlusion

 

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 Roger Holden Eye Surgeon
 
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