Understanding Refractive Lens Exchange Surgery

What is refractive lens exchange?
How does refractive lens exchange correct your sight?
When should you have refractive lens exchange surgery?

 

What is refractive lens exchange?

Refractive lens exchange, also known as clear lens extraction or PRELEX, is the correction of short-sight, long-sight, astigmatism or presbyopia by removing the eye’s natural lens and replacing it with a plastic implant lens.

It is helpful to know a little about the eye and how it works in order to understand how refractive lens exchange can be used to treat these conditions.

Anatomy of a normal eye

The cornea forms the clear window into the eye. The iris, which is the coloured part of the eye with the black pupil in the middle, is behind the cornea. The lens lies behind the iris.

In a healthy eye the lens is clear and able to focus light on to the retina, the light-sensitive nerve layer that lines the inside of the eye.

The wall of the eye is formed by three layers, the retina, the choroid and the sclera.

The choroid is the underlying vascular (blood vessel) layer of the eye, from which the retina receives oxygen and nutrients. The sclera or “white of the eye” forms a tough protective coat.

The retina sends signals via the optic nerve to the brain where sight is interpreted. This process can be likened to the lens in a camera focusing light on to photographic film, from which images can be developed.

The focusing of light by the eye depends on three main factors; the power of the cornea, the power of the lens inside the eye and the length of the eye. The cornea and lens work together to create a focused image on the retina, the length of the eye being fixed.

In short-sight (myopia) the eye is “too big” and the clear image falls in front of the retina.

 

In long-sight (hyperopia or hypermetropia) the eye is “too small” and the clear image would fall behind the retina.

In a normally-sighted eye, a healthy young lens has the ability to adjust the eye’s focus, letting us see things clearly both near and far away. Many people begin to lose this ability when they reach middle age, finding for the first time that they need a spectacle correction for reading; this is called presbyopia.

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How does refractive lens exchange correct your sight?

Refractive lens exchange alters the focus of the eye and provides clear vision by changing the optical power of the lens. This allows the image to be focused on the retina, rather than in front or behind. A multifocal or accommodating lens may then provide near as well as distance focusing.

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When should you have refractive lens exchange surgery?

There is no specific level of vision at which surgery is indicated, but if you find spectacle and contact lens dependency interferes with your daily life, the procedure could be of benefit to you.

Refractive lens exchange surgery is technically very similar to modern cataract surgery. It can now be readily performed due to major developments in the surgical technique itself, the very low risk of complications and the visual benefit of modern implant lenses.

Surgery involves removing your own lens and replacing it with a clear, plastic lens implant which you cannot feel and which remains permanently in your eye.

If you require refractive lens exchange surgery to both eyes, we will decide together which eye should be dealt with first. Surgery will be carried out on only one eye at a time, usually with an interval of one or two weeks between the two procedures.

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