The long and the short of it: How multifocal contact lenses are changing the view for presbyopic patients
Professor James Wolffsohn is associate Pro-Vice Chancellor at Aston University in the UK. His main area of study is in presbyopia research. Professor Wolfssohn will be addressing the NCLF event on 27th April to discuss the science behind the development of optical designs in multifocal contact lenses.
What are multifocal contact lenses and how do they help correct near-sightedness and presbyopia at the same time?
James Wolfssohn: Soft multifocal contact lenses are a natural progression in the development of solutions that correct both myopia and presbyopia.
With spectacles, the idea is that if you need a different refractive power at different distances, you can achieve that by simply looking through a different part of the lens. And bifocal glasses have allowed people to do that effectively for many years.
These progressed into varifocals where the optics transitioned seamlessly in one lens. But these can still produce distortions if you look off to the side - so you have to move your head in the direction you want to see.
Initially, trying the recreate the varifocals principle in contact lenses was difficult, because they are fixed to the eye. It was possible to put different optics into the lens, but you needed the lens to be able to move with the eye, which restricted you to rigid lenses. With soft multifocals we are able to split the light between distance and near, either by using aspheric design - where the power changes gradually from the centre to the outside of the lens - or a concentric design with rings of near and distance corrections moving alternately from the centre.
Because the brain is very good at ignoring blurred images, the lenses can correct both near and distance issues simultaneously.
When should multifocals be considered for a patient?
JW: We are at a stage now when most patients are suitable to at least have a conversation with their practitioner around the benefits of multifocal lenses. But every person is unique - and it is the combined near and distance aberrations in the eye determine the requirements of each patient.
Most people will use multifocal lenses in combination with spectacles, so the key is to decide whether the lens should be centred for near or distance based on a review of the patient’s lifestyle and their vision requirements. This might depend on the activities being undertaken whilst wearing the lenses - reading, sport, driving at night and so on. A practitioner can then pick a design that is best suited to individual patients.
But there are still many patients not being given the opportunity to enjoy the benefits of multifocals. Only a small percentage of presbyopic patients are in lenses of any kind, so that’s frustrating.
What are the main challenges in making multifocals more widely available?
JW: It is largely an education piece for practitioners, both in terms of getting them to buy into the idea of multifocals, and then presenting them as an option for their patients.
I use the analogy of a closet full of shoes: You wouldn’t use the same pair for all the different activities you undertake. You choose the most appropriate pair each time. With your vision, the principle is the same.
The idea you need one correction for everything you do in your life is very flawed. Different solutions are required for different occasions. Contact lenses are clearly much better options for outdoor activities: They are fixed in place, they don’t steam up and they give you more flexible movement; but glasses might be preferable for reading or other close-up, detail-focussed activities.
Some practitioners experienced issues with multifocals early in their development and have be reluctant to try them since. But technologies have moved on, and there are now no fitting or comfort difficulties. Giving a patient access to multifocals is as straightforward as putting them on any other lenses.
Equally, multifocals are a little more expensive than regular lenses - but we shouldn’t be making cost decisions for our patients - we should be providing them with all the relevant information and letting them make their own minds up.
Where do manufacturers need to focus their attention to produce even better products in the future?
JW: One of the issues we have at the moment is that, although there are several different multifocal options, they are all refractive, and therefore much of a muchness in terms of the principles the use. This means there are some patients for whom no multifocal option is available.
We have done a lot of work with interocular lenses (IOLs), which have much more range to optimise vision in any patient. IOLs are permanent lenses currently fitted to patients during cataract surgery.
The technology and level of innovation in IOLs is far ahead of contact lenses. There is more opportunity to play with the optics in each individual eye, with not only refractive solutions, but defractive, segmented, pinhole design and depth of focus options that could all be translated into contact lenses in the future.
But at the moment, the costs are too high, so manufacturers are reluctant to invest in the research.