Multifocal Lens Implants in Cataract Surgery

The following information has been given to you to assist you in making an informed decision about having cataract surgery with multifocal lens implants. Please take as much time as you wish to make your decision and please ensure you ask Professor O'Brart any questions you may have regarding your surgery and both the pros and cons of multifocal lens implants.

Background

Presbyopia (the need to require glasses for reading as you get older)

By virtue of their older ages, most patients who undergo cataract surgery also have presbyopia. Presbyopia is the process by which the lens, which lies inside the eye behind the coloured iris and its hole in the middle (the pupil), becomes harder and stiffer with age. This stiffening means it can no longer change its shape to allow the eye to focus (also called accommodation) on close/near objects. This is the reason that most people will require reading or bifocal/varifocal glasses after the age of 50, even if they have excellent unaided distance vision.

Mono-focal Lens Implants

Until recently, most of the artificial intraocular lens (IOL) implants required to replace the cloudy lens needing removal in cataract surgery, were monofocal. These monofocal lenses have only one power, or length of focus. This means that they can in most, but not all patients, be selected to correct for either distance or near/close vision but not both. The choice of whether distance or near vision is selected to be corrected, is based on each patient's individual preference, their current need for glasses and the degree of cataract in the other eye. Although it is possible with such lenses to often reduce an individual's dependence on glasses, they will still require them for some situations (typically for reading as, in most patients, the power of the monofocal lens is selected to correct for distance vision).

Multi-focal Lens Implants

Over the past decade newer lens designs have been developed to restore some of the focusing (accommodating) ability of the eye. Such lenses have the potential to allow patients to see both well in the distance while retaining near vision. Depending upon the optical features of the lenses, they are described as "accommodating", "apodized diffractive" or "presbyopia correcting". All of these lenses are "multifocal", which means they refocus some of the light for distance to allow some degree of unaided near/intermediate vision. Whilst such lenses are still relatively new, in terms of their development and usage, results have generally been very encouraging in the majority of patients.

Professor O'Brart has personally been involved with clinical research trials investigating the efficacy of some of these lenses, including the "Tetraflex" (accommodative) lens and the HumanOptic "Diffractiva" (diffractive) lens. He also has several years' experience with other multifocal lens designs, including the Alcon "Restor" (apodized diffractive) lens, the Oculolentis M Plus (presbyopia correcting) lens, the Zeiss AT LISA Trifocal (diffractive) lens, PhysIOL Finevision Trifocal lens and the AMO Symfony (diffractive, achromatic) lens. Based on the scientific literature and in his experience with such lens designs, 90% of individuals do not require spectacles either for distance, intermediate or near vision with bilateral lens implantation.

However, whilst the results with these lenses are very positive in the vast majority of patients in which they have been used, it must be understood that as yet there are no multifocal lens implants which are as good as the natural healthy human lens in a young person with its full range of accommodation. There are some compromises and differences in the quality of vision that need to be understood. These include:

It may take some time (occasionally several months) to adapt and become accustomed to seeing through the new implants
While a multifocal IOL can reduce the dependency on glasses, in some people it might result in generally less sharp vision, which may become worse in dim light or fog
Not all patients are completely free of spectacles. About 10% of patients will still require glasses for either distance, intermediate or near vision or a combination of these
Reading vision is usually very good but does depend on good lighting. Reading may not be as good in dim light
The reading distance is typically at a fairly fixed distance from your eyes so you will need to get used to moving reading material to that position or adjusting your head
Intermediate vision (computer, music) can be a little more out of focus than distance or near vision and glasses may be required for the tasks, although in most people this gets better with time. If this is a problem with the first eye, then the focal length of the second eye implant can be adjusted to try to overcome this. This is called "Custom Match" or "Mix and Match"
Visual side-effects such as circles or halos around lights, particularly at night, are not uncommon. In the vast majority of cases these phenomena, although present, are regarded as insignificant. However, in a few individuals they may cause severe problems and driving can be affected. In about 2% of cases the visual disturbances are so severe that patients may wish to have the lens removed. Lens removal requires a second operation with its associated rare risks of potentially blinding complications. If you do a lot of night driving, monofocal lenses may be a better choice for you
While the selection of the correct power of the lens implant is based upon very sophisticated equipment and computer formulae, it is not an exact science. Occasionally the focal length of the lens can settle too far in the distance or too close. This occurs because of small uncontrollable variables in the shape of the human eye and the position in which the lens finally sits in the eye after wound healing. With multifocal lens implants, even a small change in focal length can make seeing at certain distances more difficult. Usually this is correctable by changing the focal length of the implant used for the second eye. In about 5-10% of cases, however, patients may benefit from correction of any residual refractive error with "top-up" laser refractive surgery or implanting a second "piggy-back" intraocular lens into the eye
Astigmatism (a difference in the curvature of the cornea in different meridians) can be corrected during surgery by using astigmatic incisions or multifocal lenses with a toric (astigmatic) "in-built" correction. Residual astigmatism after surgery can be problematic and limit visual performance. If a residual astigmatic error remains after the surgery it can be corrected with spectacles, laser refractive surgery, lens repositioning or replacement of the lens itself
Vision typically is far better with the lens implants in both eyes rather than in just one. The improvement in vision after the second eye surgery can be dramatic
Dry eyes and oily tear films (blepharitis) can also affect the vision so it is important that these are treated to give the best result from the operation

It is important to note that whilst cataract surgery is one of the commonest, safest and sophisticated surgeries undertaken in modern medicine, no surgical procedure is 100% safe or predictable. Complications can occur due to unforeseen events during the surgery or even in the presence of totally uncomplicated surgery. Even in routine cataract surgery, approximately 1 in 100 patients may have worse vision, even with spectacles, than before the surgery, about 1 in 100 patients will require further eye surgery to treat complications and there is an approximate 1 in 1000 risk of a potentially blinding complication

Information contained on this website is intended as a guide only. Always seek professional advice before ANY treatment.
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