During cataract surgery, the natural lens of the eye is removed and replaced with an artificial intraocular lens. Much like the natural human lens, the artificial intraocular lens also focuses light coming into your eye onto the retina, the light-sensitive tissue at the back of the eye.
Most intraocular lenses are made of flexible and foldable material, so that they can be inserted into the eye through a very small incision. Intraocular lenses can be broadly divided into three types: monofocal, multifocal and extended depth of focus or EDOF lenses.
A monofocal intraocular lens has a single focus point. If you don’t mind wearing glasses for certain activities, monofocal intraocular lenses offer excellent quality of vision with minimal or no glare and halos.
Most people with monofocal intraocular lenses target for clear distance vision. This means that you can read distant signs and watch a movie without glasses. However, you would likely require glasses for intermediate distance vision (eg. using a computer) or near vision (eg. reading a book).
Some people with monofocal intraocular lenses prefer to target for near vision, which means that they will still be short-sighted or myopic after the surgery. They would need to wear glasses when they drive or walk around, but they can remove their glasses to read.
For other people with monofocal lenses in both eyes, they may prefer to target one eye for distance vision and one eye for near vision. This is called monovision. Not everyone can get used to monovision, so if you are considering this, you need to undergo further tests to see whether this is suitable for you. Monovision may reduce 3-dimensional depth perception, because you are only using one eye at a time when viewing near or distant objects.
Multifocal intraocular lenses, as the name suggests, have multiple focus points. Trifocal lenses with three focus points allow a person to have good distance, intermediate and near vision without glasses. However, this is a trade-off as the quality of vision with multifocal lenses is not as good as that with monofocal lenses. Images may appear dimmer or less vibrant, and this is most noticeable in dim lighting conditions. A person with multifocal intraocular lenses would need bright light to read well.
Multifocal lenses are also associated with haloes around lights and increased glare. This may interfere with your ability to drive at night.
Extended depth of focus or EDOF intraocular lenses are the most recent option for people undergoing cataract surgery. Instead of having distinct focus points like a multifocal lens, EDOF lenses provide a continuous focusing range between different distances. EDOF lenses allow a person to have good distance and intermediate vision without glasses, but glasses are likely required to read fine print up close. They may cause less glare and halos at night and provide a better quality of vision compared with multifocal lenses.
Both multifocal and EDOF lenses are not suitable for people with eye diseases, eg. glaucoma or diseases involving the retina. They are also not recommended for individuals with severe dry eyes. For these people, monofocal lenses are still preferred as they offer the best quality of vision after cataract surgery.
It is important to have an in-depth discussion with your eye doctor before deciding on your intraocular lens. Your lifestyle, willingness to accept glasses and the health of your eye are all factors which will help your eye doctor to choose the best lens for you.