Achieving spectacle independence or reducing spectacle dependence is a goal for many of our patients undergoing cataract surgery and it is almost always the goal with refractive lens exchange.
Refractive Lens Exchange (RLE) is sometimes also referred to as “clear lens extraction” or “lifestyle lenses” these terms all refer to the same procedure. RLE surgery involves the same steps as a cataract procedure, it involves removing the contents of the lens before a cataract has developed. The technology of IOLs has improved to the point where multifocal IOLs are so sophisticated in their design that now people are electing to have RLE to achieve reduced spectacle dependence in the absence of a cataract.
At Fendalton Eye Clinic we have been offering RLE since the late 1990s. There is no intraocular lens (IOL) that can perform like a 20-year-old natural human lens and with every option there are some compromises or side effects.
Each person is different in what they would like to achieve, and what compromises are acceptable in suiting each individual’s lifestyle needs. In making the right decision for the best IOL option for you a careful examination of the health of your eyes is necessary plus a discussion as to what you are prepared to compromise on. It is important that you advise us of specific tasks that are important to you in your life in making the right decision on the IOL that will best suit your needs.
Fendalton Eye Clinic offers three types of IOLs for reducing dependence on near vision spectacles after cataract surgery or refractive lens exchange with intraocular lenses (IOLs). These are:
1. Trifocal IOLs
2. Extended-depth-of-focus (EDoF) IOLs
3. Monofocal IOLs – to achieve Monovision or “blended vision” one eye is focused for distance and one eye for near vision.
Note: All types of IOLs are available as a toric version. Toric means that the IOL has a different curvature in different axes and hence can correct astigmatism. A toric version of any intraocular lens is more expensive due to the increased complexity of the design.
Diffractive Trifocal IOLs
This type of lens provides the most spectacle independence.
Trifocal IOLs are designed to give vision at distance, intermediate and near. All trifocal IOLs split light rays to the three focal points using diffraction grating technology. The design has asymmetrical light distribution of far 50%, intermediate 20% and near 30% foci.
Trifocal IOLs are best suited to people who want the maximum possible freedom from spectacles but are prepared to tolerate night vision disturbances including halos around lights and starburst (a light looks like a large star).
Feedback from our patients and published studies reinforce findings that about 95% of those with a trifocal IOL are independent from spectacles and 97% are happy or satisfied. About three percent will not be as satisfied or be dissatisfied. The main reasons include:
1. Halos, starburst and glare particularly evident at night-time
2. Some people simply take longer to adapt to trifocal IOLs but in most cases will do so with time
Extended-Depth-of-Focus (EDoF) IOLs
The aim of an EDoF IOL’s is to give good unaided distance vision and useful intermediate range vision (arm’s length vision eg. a computer screen, car dashboard) but without the optical side effects common with Trifocal IOLs. However spectacles are required for reading.
The EDoF intraocular lens that Dr Kent uses are the Alcon Vivity, the design works on a change in the geometry of the centre of the optical part of the IOL, centrally in the lens there is a slightly elevated plateau that stretches and shifts the wavefront to provide a continuous range of focus. With a very low incidence of adverse night time visual side effects. Expected results are good unaided distance and useful intermediate (arm’s length) vision. Reading spectacles are likely to be required to read small print.
Monovision with monofocal IOLs
Monovision is where one eye can see clearly in the distance and the other eye is intentionally made short-sighted so that it has either near reading vision (full monovision) or intermediate (arms-length) distance vision (limited monovision). With both eyes open the eyes work together to “blend” the vision providing good distance through to close range vision. It is a good option for those who have successfully practiced monovision with contact lenses and are happy with it.
We only use monovision with monofocal IOLs in patients who have practiced monovision with either contact lenses or following laser refractive surgery or have had it naturally and want to continue with the same.
Monovision pros and cons
Monovision does focus your two eyes at difference distances, and this may affect binocularity or the ability to judge depth or distances.
Monovision is a compromise because the distance eye does not read without glasses and the near eye cannot see in the distance. There may still be times when top-up glasses will be required such as:
• Driving a car in poor light conditions, particularly when it is raining.
• Prolonged reading, as it can be tiring to read with only one eye.
Published studies have shown about a quarter of patients given monovision with monofocal IOLs are spectacle independent.
The main advantages of monovision are that using modern aspheric monofocal IOLs usually gives good optical quality without halos, ghosting or glare. With monovision you can still wear glasses that correct both eyes for distance or both eyes for near vision and achieve good optical quality.
If you have to meet specific visual standards to conduct your work you must check with the authorised governing body if they have any policy relating to specifications or recommendations around intraocular surgery.
There is no intraocular lens that can perform like a 20-year-old natural human lens and with every option there are some compromises or side effects. Each person is different in what they would like to achieve and which compromises might suit their individual lifestyle.
If you would like further information on the IOL choices outlined above please contact us for further specific advice. Alternatively you can book a free assessment with a member of our technical team to find out more regarding your suitability for a refractive lens exchange procedure.