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Intraocular lens

There have been tremendous technological advances in intraocular lens design over the past few years. The Vision Practice ensures that our patients benefit from these new technologies by offering a full range of intraocular lenses. Different lens types can be chosen to deliver the best possible vision following surgery. In the past, cataract surgery and refractive lens exchange procedures have been performed using only single focus lens implants. While this choice is still suitable for many, other types of recently developed implants can offer significant advantages. Intraocular lenses are commonly made of rigid or foldable materials although rigid materials are not suitable for use in small incision surgery. The Vision Practice uses lenses manufactured from hydrophobic acrylic which is a foldable material with a very long track record of safety. Your consultant will help you choose the best lens option for you, a process which will involve matching the lens design to your requirements, taking into account the biometry data. Four different designs of lens are offered by The Vision Practice:

AcrySof Single Focus lens
My current preferred single focus lens is the AcrySof lens. It has an excellent track record of safety and has excellent optical properties. This lens will usually allow you to achieve very good distance vision without spectacles, or if glasses are required, they are likely to be low power. You will almost certainly need reading spectacles or bifocals/varifocals if you prefer to use a distance correction. I use the latest version of this lens which incorporates aspheric optics to improve definition.

AcrySof IQ Single Focus lens with yellow filter
Manufacturers have introduced lenses containing yellow filters, which selectively reduce transmission of high energy blue light. I currently offer the AcrySof IQ which is a single focus lens with a yellow filter of this type. The lens also has aspheric properties which can improve image definition. The lens is designed to closely simulate the light filtering properties of the natural lens of the eye. All lenses contain a filter to remove harmful ultraviolet rays. It has been proposed that lenses containing yellow filters reduce the amount of harmful high energy blue light reaching the retina, which may have a theoretical benefit in reducing the progression of macular degeneration. These theoretical benefits have not been proven, although it is certain that lenses containing yellow filters do more closely match the light absorption properties of the natural human lens.

AcrySof Toric lens
This lens offers the ability to correct astigmatism reliably and predictably. Before the development of this lens, astigmatic correction required additional incisions on the eye which had less predictable and more unreliable outcomes. Astigmatism is caused by the curvatures of the eye (most commonly the front clear window of the eye or cornea) not being equal in all directions (or axes). It can also be contributed to by astigmatism within the natural lens. If corneal astigmatism is present, curvatures to counteract these variations can be incorporated into glasses or contact lenses. In your glasses prescription, astigmatism is expressed at ‘Cyl’, an abbreviation for cylinder, as in this example showing astigmatism of 2.75 diopters.

The Toric lens has the ability to correct not only long and short sight but also astigmatism and is now available to correct very high astigmatic values. When used in combination with techniques of planned incision placement, degrees of astigmatism up to approximately 3.0 diopters can be corrected. This should give you good distance vision without glasses, but you will still need reading glasses. The lens is made from the same AcrySof material as the other Alcon lenses with the same track record of safety. It does contain the yellow filters found in the AcrySof IQ. As with toric (or astigmatic) glasses or contact lenses, the lens requires very accurate rotational alignment. This requires an additional step of marking the astigmatic axes whilst you are sitting up, before commencing surgery. After this, surgery is identical although the lens must be carefully lined up in the correct axis once placed in the eye, using axis marks on the lens placed by the manufacturer. Once correctly placed in the eye, significant rotational movement of the lens in the eye is very rare.

AcrySof PanOptix and Toric PanOptix
The AcrySof PanOptix trifocal is an exciting new multifocal intraocular lens. It offers the chance of achieving spectacle independence for clear distance, intermediate and reading vision, without glasses. The lens is also equipped with aspheric optics incorporated to improve image definition.

The lens is designed to achieve comfortable near and intermediate vision as well as distance vision and achieves this using trifocal technology. One of the early drawbacks with multifocal lenses was that intermediate vision without spectacle correction was not as strong as distance or near vision. The PanOptix is designed to address this, offering a good quality of vision at a full range of distances.

Multifocal lenses are not suitable for everybody. Multifocal lenses can cause a slight loss of contrast. This is usually insignificant but you may find you need proper illumination to read in a dimly lit room. Glare around point sources of light such as car headlights is also sometimes reported but this is rarely troublesome. This lens usually delivers very good distance, intermediate and reading vision. On occasion spectacles can be required for very detailed near work. The symptoms of glare and halo effect around headlights are usually mild and the lenses have been used successfully with varied visual requirements.

The PanOptix lens does incorporate a yellow filter. The lens is most suitable for those planning surgery on both eyes, although surgery on one eye can be performed in special circumstances. Toric PanOptix lenses are available with astigmatic correction, allowing their use in cases where mild to moderate astigmatism is present. PanOptix lenses do cost significantly more than standard monofocal lenses.

The Symfony and Toric Symfony by Johnson & Johnson Vision
The Symfony is a popular lens offering an extended range of vision. It is not a true multifocal implant but instead delivers an extended range of vision, dramatically reducing spectacle dependence. The lens typically delivers good distance vision and intermediate vision. By carefully planning the refractive outcome of each eye it is usually possible to deliver distance vision, intermediate vision and some reading vision, although you should expect that reading glasses will be required for small typefaces, or prolonged reading.

Whilst some glare and halo effect is experienced this is usually limited and is certainly less than earlier models of multifocal implants. The Tecnis Symfony delivers an extended range of vision in all lighting conditions and is less dependent on good light than earlier multifocal designs. The Symfony does have the strength of offering quite a natural visual experience. Reports of glare, whilst present, are certainly less than the symptoms reported with other multifocal designs. The intermediate vision is typically quite strong, often permitting the use of a computer without spectacle correction.

The Symfony typically offers a high degree of spectacle independence, although spectacles may be required for small print. A Toric (astigmatic) model of the Symfony is available allowing the use of this lens in cases where mild to moderate degrees of astigmatism are present. The Symfony lens is also particularly suitable when there is a very high pre-existing spectacle prescription. In these circumstances it can be very difficult to guarantee achieving zero spectacle prescription following surgery, and the Symfony lens does deliver good vision without spectacles, even when there is a small residual spectacle prescription.

 
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  Specialist cataract surgery & refractive lens exchange procedures | John Greenwood Consultant ophthalmic surgeon | © 2018 The Vision Practice. All Rights Reserved.