The first ever intraocular lens (IOL) was successfully implanted in a patient at St Thomas’ Hospital in London by Sir Harold Ridley on 29th November 1949 and ever since surgeons have discussed and researched the best surgical lenses to use. A staggering 67 years later, and with huge advances in the technique of implanting an intraocular lens and the lenses themselves, the discussions continue. Now we are debating monovision IOL implants versus multifocal IOL implants for presbyopia.
An intraocular lens implant is mostly used in older adult patients who have developed cataracts or myopia. IOLs are implanted in the eyes and can be offered in a monovision or multifocal variation. Each type of lens has its own assets and flaws. The eye doctor/surgeon will always recommend what they think is the best and safest lens for you, as what is good for you may not be for someone else. In this article I will go through the differences between monovision and multifocal IOL implants.
Monovision IOL Implants
Monovision is one of the ways we can treat presbyopia, in which we implant a monofocal IOL in both eyes but not the same way. An IOL can be implanted so to give near, intermediate or distance vision. When we carry out a monovision implant procedure one eye is corrected for distance vision and the other eye is corrected for near or intermediate vision.
This might appear to be problematic at first but your brain is able to do something extraordinary when eyes are corrected with monovision implants. The eye that is corrected to give distance vision will give the distance image to the brain, while the other eye, which is corrected to give closer vision, will give that image to the brain and the brain is able to merge the two together to make a whole. This may take a little while to get used to and for the brain to adjust to the new monovision at first. The eye clinic can normally demonstrate this to you to see how you cope with this effect.
Due to the fact that the monofocal monovision implants do not split light entering the eye they are better for night driving as you do not get as much glare and halos from light as patients with multifocal implants. Also as you have a fixed focal point on each eye with monovision, they tend to perform better with intermediate vision, such as using a computer. The downside to monovision is that it is a compromise and some people will love the effect while others are unable to get along with it.
Multifocal IOL Implants
Unlike monovision IOL implants where each eye has one focal point, multifocal implants work like a progressive lens. On a multifocal implant the lens itself has many circles around it at different points to give distance, intermediate and near vision in both eyes the same. The circles on the multifocal implants splits light entering the eyes so you can focus on whichever distance you are looking at, whether that be close up or an object in the distance. The point of a multifocal implant is so you will not require the use of glasses or visual aids during your day-to-day activities. Just like the monovision implants, multifocal implants take a little time to get used to. The brain will need to relearn to find the correct point for near, middle and far distances.
What are the benefits?
Benefits of multifocal IOLs is that both eyes are focusing on the same distance which many patients prefer but due to the splitting of light you may suffer from glare and halos around lights. Many people who have cataracts suffer very much with halos and with multifocal implants the halos are often much less than this.
With both monovision and multifocal implants there is no guarantee of complete freedom from glasses, you may need them for reading very small print for example.
When having a consultation with an eye doctor or optometrist for IOLs, it is very important for you to consider what your expectations, goals and needs are. Your surgeon will only recommend what they think it safest and best for your eyes , that meets your requirements.