What are multifocal intraocular lenses?

As vision deteriorates, many people opt for multifocal intraocular lenses to improve their sight. Leading consultant ophthalmologist Mr Alexander Ionides discusses when they are required, benefits and the advantages.

What is a cataract?

A cataract is a cloudy lens. When we remove the cloudy lens at the time of cataract surgery, the cloudy lens is replaced with a clear, plastic (usually acrylic) lens implant that focuses light onto the retina to allow us to see clearly.

What are multifocal intraocular lenses and what are they used for?

Monofocal lenses focus for one distance only, usually for far distance, allowing people to see more clearly for driving, watching television and walking around. However, even with the use of such lenses, patients will also require glasses for reading and close work, including the use of desktop computers, books and mobile phones. 

Manufacturers are currently working on multifocal intraocular lenses (IOLs). These acrylic multifocal lenses cannot change their shape as the natural lens can before presbyopia sets in, so the manufacturers have 'etched' a reading 'add' on to the lens.

When are multifocal intraocular lenses required?

Multifocal intraocular lenses are usually required when people are struggling to read. Presbyopia occurs at the age at which the inability of the natural lens to focus gives rise to the need for reading glasses. The age at which this happens is usually about the mid-40s. 

There are different designs of reading adds that get 'etched' on to the lens and they embrace slightly different theories of optical physics to achieve this. The lens is designed to focus on distant vision, while the reading works to correct nearsightedness. The term "trifocal" denotes the lens's ability to focus on three distances: near, intermediate (such as a desktop computer), and far distance.

The more rings, the better the reading vision. However, when looking at point sources of light such as an oncoming headlight on a car, or lamplights in the night, as the light passes through the lens with these rings, or circles 'etched' on to the lens, the lights can appear to have rings or haloes around them.

During the day these symptoms are less intrusive but at night when point sources of light pass through the lens it can appear that lights have got halos and rings and around them. These symptoms can get less with time but in some people they persist. 

What are the advantages of multifocal lenses?

Multifocal lenses permit us to be much less reliant on reading glasses. In fact, in some cases, they allow us to be completely free of the need for reading glasses.

The advantages of the multifocal lenses are that we are much less reliant on reading glasses, in some cases almost completely free of the need for reading glasses. As we age and experience increasing physical limitations, this can significantly enhance our overall quality of life.

However, the rings and the halos can be debilitating for some people at night, such that it is not possible to drive. For this reason, manufacturers have designed a group of multifocal IOLs called extended depth of focus (EDOF) lenses that have fewer rings on them. Fewer rings result in fewer halo at night: However, unfortunately, this results in less reading, and therefore requires the need for reading glasses for small or close print.

The extended depth of focus (EDOF) lenses fall in between trifocal and monofocal lenses. Some lenses opt out of the ring design and instead incorporate a reading add on only one portion of the lens. It's important to note that a higher reading add can lead to a greater reduction in vision quality. While monofocal lenses still offer the best vision quality, ongoing advancements introduce new multifocal lens designs aiming to provide improved near vision with minimal compromise in visual quality.

Individuals without cataracts may choose refractive lens exchange, a form of cataract surgery performed without cataracts. This procedure involves implanting a multifocal lens to eliminate the constant reliance on glasses.

Who can benefit from multifocal lenses?

It is most beneficial to patients such as hyperopic people, those with a 'plus' prescription in their distance spectacles.

Hyperopic people require 'plus' glasses for distance and even stronger 'plus' glasses for near-sightedness.

The multifocal intraocular lens implant frees individuals from the need for distance and most near-vision glasses. While night-time halos often diminish over time for the majority, the benefits of the multifocal lens generally outweigh any drawbacks, resulting in satisfaction with improved vision. However, a minority may not experience improvement in halos, posing a significant challenge to their night vision.

If you would like to book a consultation with Mr Ionides, do not hesitate to do so by visiting his Top Doctors profile today.