Monovision cataract surgery or multifocal intraocular lenses?
What is monovision cataract surgery?
Monovision cataract surgery is a technique to reduce the dependance on glasses and contact lenses. Usually the dominant eye is set for distance vision and the second eye set for nearer vision for reading. This is done when choosing the intraocular lens (IOL) due to be used during the cataract surgery. The aim is to increase spectacle independence with glasses free vision for distance and near. Another method of doing this is to have multifocal IOL placement whe having your procedure. You may still require glasses when reading for prolonged periods of time or when using intermediate vision such as watching TV and night driving.
It is classified as a type of refractive surgery. Monovision lenses used as a replacement of the eyes natural lens have the advantage of clear vision at different distances for each eye. Monofocal intraocular lenses are one of the surgical options for reduced dependance on glasses.
Monovision is used in laser vision correction lasik surgery and in contact lens correction. It is not just confined to cataract surgery. Monovision lasik has been around for many years. Pseudophakic monovision following cataract surgery is an established practice that is effective in the right patients. It is also used in refractive lens exchange where cataract surgery is performed before the cataracts develop to give reduced glasses dependance.
What is Mini Monovision?
Mini monovision is where the dominant eye is set for distance vision and the non dominant eye is set for slight near vision so that you can reduce the need of spectacles for looking in the distance, using the computer and general activities. You may still require glasses for reading and night driving.
How does monovision work?
With one eye set for distance and the other set for near, the two eyes have different focusing powers to give a blended vision that works at different distances.
When focusing on the distance:
The brain partially suppresses the image it receives from the eye set for near giving good distance vision
When focusing on the near
The brain partially suppresses the image it receives from he eye set for distance gibing good near vision.
How long does it take to get used to monovision after cataract surgery?
It can take about 6 weeks to get used to monovision after cataract surgery. For patients who have had monovision contact lenses before this can be quicker whilst in others it can take a few months.
How successful is monovision after cataract surgery?
About 90% of patients find much reduced spectacle dependance after monovision cataract surgery. Most are able to carry out their daily activities without glasses but require glasses for some visual functions. On the whole patient satisfaction can be high if there has been a clear discussion and explanation of expectations prior with your cataract surgeon before the operation.
Is monovision a good idea?
Monovision is a good idea for those who want extended vision and reduce the use of glasses. It is done with a type of intraocular lens known as a monofocal lens. Monofocal lenses differ from multifocal intraocular lenses in that they have less glare and halos and give higher contrast sensitivity. The depth of focus is lower with a monofocal IOL than a multifocal IOL.
Who is a good candidate for monovision?
You are a good candidate for monovision if:
You want to reduce your dependance on bifocals following surgery
You don't like or cannot wear contact lenses
You do activities which mean wearing glasses is very inconveient
You want to see without glasses for distance and near
You have used monovision contact lenses before
You are not a good candidate for monovision if:
You have a history of a lazy eye
You have double vision
You require extremely fine vision like a pilot
You have astigmatism that you are not wanting corrected
You have other medical conditions that affect the vision such as advanced glaucoma, diabetic retinopathy, or age-related macular degeneration.
You have a history of stroke that has affected your vision.
You have alway had cataract surgery to one eye wit a multifocal intraocular lens
Do you loose depth perception with monovision?
There is a slight decline in depth percetopion with monovision. With monovision one eye is set to see distant objects clearly and the other set at a strength similar to reading glasses. This means there is some reduction in stereo vision as whatever you are looking at will look blurred with one eye and sharp with the other. This affects the depth perception. You adapt may using visual clues to judge depth such as the size of the image and whether they are near things that are obviously far or near. The change in depth perception with monovision surgery is one of the sacrifices made to reduce spectacle dependence.
Does monovision affect driving?
Some patients feel that monovision does not affect their driving and are able to meet the legal requirement of reading a number plate at 20 metres and have good depth perception. Some who are happy to drive during the day are uncomfortable to do so at night. The greater the difference between the two eyes the greater the more likely it is to affect driving. Many people keep a pair of glasses in their care for a backup incase they need them to drive. If monovision does affect your ability to drive you will need to wear glasses.
Are multifocal lenses better than monovision?
Multifocal lenses are no better than monovision. They just serve a different purpose. In both cases patients should have a good visual acuity. Refractive surgeons may suggest monovision if you are not comfortable with the idea of progressive lenses such multifocal lenses. These can cause glare, halos and reduced contrast sensitivity in poor light due to the spherical aberration within the lens. Multifocal lenses aim to give glasses free vision for near, intermediate and distance vision. Monovision aims to give clear vision for distance and intermediate vision with each eye doing focusing something different to give a blended vision. Some studies report monovision is better at distance and intermediate vision whilst others report multifocal being superior. Ultimately it depends on you and what you want most out of the surgery.