Intraocular Lens Selection
Ok, so you have had your consultation and it has decided that a cataract or clear lens surgery is your best option to improve your quality of vision. The next decision to make is what sort of implant lens you would like to have. Implantable lenses have been routinely used for many years, and now there are many choices available. Virtually no modern cataract surgery is done without placement of an implant lens at the end of the surgery. They are made of a soft flexible plastic to allow implantation through a tiny 2mm incision, and are properly called Intra-Ocular Lenses, or IOLs for short.
To make your decision easier we only offer the best and most reliable IOLs currently available. This includes using a toric IOL if there is any significant astigmatism. We have no commercial arrangements with any device or drug companies. This information sheet is meant for people with healthy eyes who are interested in reducing or eliminating their need for glasses after cataract or clear lens surgery. If you have other problems with your eyes such as macular degeneration, glaucoma, corneal transplant etc then some of these IOLs won’t be appropriate for you.
Choice of IOL comes down to what is important to you with your vision afterwards. It depends on your age, occupation, hobbies and personality. Of course everyone would like to have the perfect vision of a 20 year old after surgery. This is unfortunately not possible, but with modern IOLs we can get pretty close!
There are 3 main choices:
- Both eyes distance vision
- Monovision or blended vision
- Multifocal IOL
1: Both Eyes Distance Vision
This is the traditional method of implanting IOLs. It will give you excellent distance vision but usually minimal close vision without reading glasses. All IOLs have some range over which they will see clearly, but younger people (<70) with larger pupils will usually have a limited depth of clear focus. This option may be best for people with other problems with their eyes such as macular degeneration or glaucoma to maximise their visual quality. For people with healthy eyes though it can be somewhat limiting as reading glasses or multi-focal glasses will be needed for most tasks such as using a computer, reading your watch or phone or even eating food off a plate. For those who are happy to wear glasses this is the simplest and safest option and does give the clearest distance and night vision possible.
2: Monovision or Blended Vision
This means having one eye (strongest or dominant eye) set for distance and your other eye set for close. This may sound a bit strange but for many people will give them the best of both worlds. Most people’s brains are quite good at picking and choosing between the vision in each eye and will focus on the sharpest eye for each task. For example, if your right eye were set for distance and you were driving you would use your right eye to look down the road and your left eye when you look at the speedometer. This happens automatically without you thinking about it. If the near point is set too close then reading will be excellent, but overall distance vision can be compromised. Because of this the near point is usually set at mid arm’s length. This results in minimal compromise in distance vision, and good intermediate vision for things like computer use. With good light most people can read quite small print such as newspapers or magazines, but very fine print or reading in dim light may require occasional reading glass use. Another advantage of monovision is that for occasional highly demanding visual tasks, such as driving at night in the rain, you can wear corrective spectacles over the top to restore perfect binocular vision. Most people will never need to do this, but it can be reassuring to know you can if you have to. Monovision is also great for activities that need perfect vision in one eye at a time such as using a camera, a rifle sight or telescopes and microscopes.
Monovision can be easily tested before deciding by wearing a contact lens in each eye for a few hours or a few days to simulate the effect. This gives a good indication of expected vision after surgery, but there can be some time to adapt, so things get easier and better for a few months afterwards. If you like monovision after a day you will love it after 3 months. Some people though will never adapt to the difference between the 2 eyes, which is why trialling first is a good idea. There will often be some reduction in depth perception and peripheral vision, though with time this usually becomes difficult to notice.
A slight variation is mini-monovision. This simply means that your reading eye is set a bit further away, so reading glasses use is more frequent, but distance vision is excellent. This suits people who need very good distance vision, depth perception and peripheral vision but want some independence from glasses. With this option the reading eye will often see 20/20 on the distance chart, and the distance eye even better.
3: Multifocal Intra-Ocular Lens
Multifocal IOLs have been available for many years, but until recently the visual compromises have been significant. Early multifocal lenses were bifocal, that is they had two focal points. The near point was usually very close, and intermediate tasks such as computer use could be poor. Some people experienced significant loss of sharpness, referred to as “waxy vision”. The latest multifocal lenses are dramatically better, with much better quality and range of vision. The most commonly used multifocal IOLs now are trifocal, so have three focal points. This allows both eyes to see and work together for distance, intermediate and near. This allows better peripheral vision and depth perception than with mono-vision, and is better suited for people who struggle to adapt to the difference in focus with mono-vision. It also allows better close vision than with mono-vision, and is usually excellent for near tasks like reading, sewing and wood working. Multi-focal IOLs work all the time while looking in any direction. They are very different to multifocal glasses which require you to look through different parts of the spectacle lens depending on what you are trying to focus on.
Trifocal IOLs have a diffractive design, which means there are multiple circles etched on the surface of the lens. These will manifest as halos around lights at nighttime, such as car headlights and street lamps. They can also cause a sparkly appearance around bright reflected lights during the day. Most people find these phenomena to be minor, but occasionally they may be noticeable enough to influence night time driving.
The newest type of multifocal IOL are the extended depth of focus IOLs. The 2 main ones used are called Symfony and Oculentis. Extended depth of focus IOLs generally have less effect on night time vision and driving than trifocal lenses but near vision is reduced, so reading glasses may still be required. Intermediate vision is generally very good.
Unfortunately there is no way to find out before hand how significant the visual symptoms from multifocal IOLs will be. Some people will experience a noticeable loss of sharpness in their vision with multifocal IOLs, which is not correctable with glasses. Most people though will find sharpness to be excellent. Many people find their reading vision easier with better light. There can be an adaptation period of several months where the halos reduce in intensity, but many people find their vision excellent straight away. Unfortunately there is a small minority of people who may never fully adapt to their vision with multifocal IOLs and in very rare cases this will be significant enough to warrant removal of the IOLs and replacement with traditional single focus lenses.
Many people will be very happy with their vision no matter which option they choose. For people who need excellent distance vision and don’t mind wearing reading glasses, bilateral distance or mini-monovision is usually best. For people who are very happy with their monovision contact lens trial monovision will give a very predictable safe result. If there are some circumstances such as close reading or perhaps difficult night driving where vision is inadequate, a pair of glasses will allow perfect vision. Multifocal IOLs are the latest technology available and allow both eyes to work together, giving very good distance, intermediate and close vision as well as peripheral vision and normal depth perception. The halos, sparkles and occasionally loss of sharpness may bother some people though and glasses can not correct this. Multifocal IOLs are best suited for people with healthy normal eyes. They may degrade image quality in the presence of other eye problems such as macular degeneration or diabetic eye disease. People who work in dark environments with multiple light sources, including extensive nighttime driving may be more symptomatic. Photographers, artists, pilots and professional drivers may prefer the purity of single focus implant lenses, but many others will find the convenience and range of vision allowed by modern multifocal IOLs is worth much more than the downside of halos and sparkles.
You should feel free to ask us any questions about these options. It is important to try and make the right decision before surgery as replacing IOLs is much riskier and more difficult than putting them in in the first place! Those who expect perfect distance, intermediate and close vision with no compromises may be better off waiting 20 years for the technology to catch up. For those who are prepared to accept the above minor compromises current IOL technology allows potential for great vision and either no glasses or greatly reduced need for glasses.