The guide to intraocular lenses

In this article, consultant ophthalmologist Mr Hussameddin Muntasser explains the different kinds of intraocular lenses and their applications.

What are intraocular lenses?

During cataract surgery, a patient is usually offered a synthetic lens, called an intraocular lens (IOL), to replace the natural ones in the eyes. Cataracts form when the eye’s lens, behind the cornea, gradually turns cloudier as its proteins degrade. The lens’ purpose is to focus sight, and when they become dysfunctional, the vision will become blurry and indistinct. They typically occur in people aged 40 and upwards.

The procedure involves a small incision made on the surface of the eye, through which the surgeon can access to remove or destroy the defective lens and replace it with the IOL. They can be used to correct refractive errors like astigmatism and myopia in addition to cataracts. One of the major benefits of IOLs is because they’re synthetic, they cannot form cataracts again. There are a variety of different IOLs, and cataract surgery patients can select which kind they want based on their needs and lifestyles.

What are the types of intraocular lenses and how are they used?

Monofocal lenses

The basic lens used in NHS cataract patients is the mono-focal intraocular lens. These lenses aim to offer an excellent vision for distance, but their focal range doesn’t cover near or mid-distance, so if you feel you want to be able to see without glasses when using your mobile phone or looking at the PC screen or car dashboard, or even looking at the ball when playing golf, then there are other lenses that can help with that

Toric lenses

Many people who use glasses have astigmatism, this is related to the shape of the cornea where they have a complex glasses prescription – in this case, a Toric lens might be the only option to help them become less reliant on glasses for distance vision. As we get older, our ability to focus our eyes on close-up objects will deteriorate over time, because we can no longer change the shape of the natural lens inside our eyes.

Multifocal lenses

A mono-focal lens will not help us see near as well as distance, but we have other options now that help us become less reliant on glasses even for near vision. Multifocal lenses set different focal points for near, mid, and far distances.

The usual side effects that can come with multifocal lenses are reduced contrast sensitivity which would be more prominent at night – almost all patients who receive this implant can expect some light distortion such as halos, starburst and glare. This usually resolves after a few weeks, and all but a few people would not find them bothersome or even noticeable.

Extended depth of focus lenses

Extended depth of focus (EDOF) lenses provide focus for distance and mid-distance in a continuous range and are associated with fewer side effects than multifocal lenses. These lenses are used to correct presbyopia, which is when the eyes cannot focus on nearby objects. These lenses work by creating a single elongated focal point to extend the range of vision.

However, the technology is always improving, and now there are new sets of lenses available that offer the advantages of both multi-focal and EDOF lenses.

There are many different types of lenses, including the material they are made of and the technology they employ, and each patient needs to be assessed individually to choose the right lens for them. In terms of lens material, hydrophobic lenses are better, and in terms of technology I prefer extended depth of focus lenses – such as Vivity from Alcon – as they are associated with fewer side effects. New lenses – such as Ryaner’s Galaxy lenses – offer the best of both worlds with fewer side effects than those of multifocal lenses.

Even though all these designs, whether mono-focal, Toric, multifocal or extended depth of focus lenses, are designed to remain in the eye permanently and don’t need any changes over time, the shape of the eye can change after a few years, and some people will require glasses for some tasks.

Regardless of whether the patient chooses to have mono-focal or advanced technology lenses, precision and meticulous attention to detail at each step help to achieve the outcome preferred by the patient.

If you are considering lens replacement surgery or are struggling with other visual impairments, you can consult with Mr Muntasser via his Top Doctors profile.