MULTIFOCAL IMPLANTS FOR REFRACTIVE LENS EXCHANGE/CATARACT SURGERY.
1/ Same risks as for cataract surgery.
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, 1 in 100 cases may have worse vision even with spectacles than before the surgery, 1 in 100 cases will require further eye surgery to treat complications and there is a 1 in 1000 risk of a potentially blinding complication.
2/ We aim to try and get patients spectacle independent 80% of the time. In low light conditions and at the computer, glasses may be needed.
3/ Most patients have good newspaper vision– 85%. Not all patients are complete free of spectacles. About 10% of will still require glasses for either distance, intermediate or near vision or a combination of these.
4/ Some double vision is common initially. There are two images in the eye, one for far and one for near. When looking at an object at a distance, near focus is blurry, and the brain has to learn to get rid of the near focus. It is the other way around when reading. It is important that patients understand this concept.
It must be understood that as yet there are no Multi-focal 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.
- 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.
- Visual side-effects such as circles or haloes around lights particularly at night are not uncommon. It 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 Mono-focal 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 Multi-focal lens implants, even a small change in focal length can make seeing at certain distances more difficult. In about 5-10% of cases, however, patients may benefit from correction of any residual refractive error with “top-up” laser refractive surgery, incisional surgery or a 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 Multi-focal lenses with a toric (astigmatic) “in-built” correction. Residual astigmatism after surgery can be problematic and limit visual performance. If residual astigmatic error remains after the surgery it can be corrected with spectacles, laser refractive surgery, or 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.