Intraocular lenses (IOL): which one is right for me?

An intraocular lens (IOL) is an artificial lens that is implanted into your eye to help improve your vision. This can either be at the time of cataract surgery (to replace your natural lens which has become cloudy) or as an “upgrade” to reduce your need for glasses/contact lenses.

Nowadays, there are many to choose from and the right one for you will depend on many factors, including your specific visual needs. Mr Dan Lindfield, a leading consultant ophthalmologist and cataract surgeon in Guildford and Farnham, Surrey explains the pros and cons of the different types of IOLs and what to expect before and after surgery.

What conditions can intraocular lenses treat?

Many of us wear corrective lenses to enable us to see clearly for distance, intermediate or near activities. These can take the form of glasses or contact lenses.

Cataract

In certain situations, the natural lens inside the eye can be “upgraded”, reducing reliance on the need for glasses or contact lenses. Often this is performed when a cataract forms.

A cataract is the age-related clouding of the lens inside our eye. It tends to occur when we reach 60 years or older but it can occur at a younger age in rarer circumstances. Cataract surgery involves removing the cloudy lens and replacing it with a precision-made implant.

Refractive lens exchange 

Some patients aged 45+ may also be eligible for refractive lens exchange (RLE). RLE is essentially a cataract operation, but it is performed before a cataract has formed to reduce dependence on glasses.

Both procedures take approximately 10 minutes and can be performed with an eye drop anaesthetic only, removing the need for injections. The whole hospital visit often takes about 90 minutes from arriving to going home.

What are the different types of intraocular lenses?

There are two main types of lens: monofocal and multifocal/trifocal. Both types are also available in toric (astigmatism reducing) variants.

Monofocal lenses

These implants can allow excellent visual function at a set distance. They can correct shortsightedness or longsightedness. They aim to leave patients without glasses for a defined focal length, which is usually for distance vision.

They are available in small incremental strengths to enable surgeons to leave patients as close to their perfect prescription as possible. Aiming for a prescription of 0.00 means that distance activities can be seen without glasses - this includes day to day life, driving and TV.

Monofocal lenses perform very well in low sun, dim light or in the presence of other eye diseases (which may preclude the use of trifocal lenses).

Patient satisfaction with monofocal lenses is high and very few negative effects have been reported. However, enabling a change of focal length (e.g. for reading or computer use) often requires the addition of reading glasses.

Monovision or mini-monovision

This is a technique to allow the benefits of monofocal lenses (relatively low cost and very low risk of adverse visual effects) whilst reducing the need for reading glasses.

The dominant eye is set for distance and the non-dominant eye is set for varying amounts of nearer vision. The two eyes perform different tasks when measured on their own but when both eyes are open they allow a seamless range of vision. The ability to read without glasses depends on how close-focussed the non-dominant eye is set.

Greater differences between the two eyes can allow for complete freedom of both reading and distance glasses for some patients but with the increasing disparity between the eyes, there is an increased awareness of the two eyes being imbalanced. This technique can be discussed with your surgeon along with tests to identify which eye is dominant. Mr Dan Lindfield explains that it is not suitable for all patients and takes skill, experience and judgement to perfect this technique.

Trifocal lens

These state of the art implants potentially allow for complete freedom of glasses. However, in practice, most patients feel that they are less dependent on glasses but still occasionally use them for prolonged periods of close work, such as reading a good book.

These lenses carry significant extra cost because of their design complexity and relative rarity. They work by simultaneously providing the eye with three focal lengths of vision; distance, intermediate (computer screens) and near and then asking your eye and brain to “tune in” to which objects it wants to see.

There is often a learning curve associated with these lenses but within a few weeks, patients can often see clearly for distance and near tasks. It must be stated, however, that these lenses function their best in good light. They sometimes perform less well in dim light.

Approximately 5-10% of patients are also aware of “rings” or “circles” in their vision when viewing bright lights such as car brake lights. These rings emanate from the circular zones on the lens surface which allow for the trifocality. The glare from these rings is rarely troublesome but can be noticeable.

Trifocal lenses can be well suited to you but Mr Lindfield reassures that he or your chosen doctor will go through a process to ensure they fit with your requirement and your eyes are suitable.

What are intraocular lenses made of? Are they safe?

Intraocular lenses are made from different forms of plastic-like material. Each manufacturer has its own specific design but the plastics have a long track record of safety with proven results. 

They are very safe. Millions have been implanted worldwide and the risk of problems is exceptionally low. 

They are produced in sterile medical facilities and many lenses are not even handled in theatre. They are injected into the eye via a sterile introducing device without requiring the lens to be handled by the surgical team. 

They have no “shelf life”. Once implanted they will last a lifetime and do not require changing in the future.

What should patients ask their eye specialist about IOLs?

I definitely recommend patients ask their surgeon which lens they think is right for them. Your surgeon will have many years of experience and will know what is most appropriate for your eye, lifestyle and expectations. There is a lot of science here but lens selection is also an art and a skill.

Whilst hearing positive or negative opinions from your friends or family is useful, it’s very difficult to draw parallels for such a precise decision targeted to your specific needs.

Also, feel free to ask your surgeon about their PCR (posterior capsular rupture) rate. PCR is the most commonly used metric for judging surgeon skills and experience. All surgeons are nationally benchmarked. It can be as high as 2% or occur very rarely. Most top surgeons have rates less than 1 in 1000 (or lower). For example, my personal PCR as a surgeon is 0.03% (1 in 2900) which places me in the top 1% in the UK.

How are patients prepared for the procedure?

Cataract surgery and RLE take approximately 10 minutes per eye. We usually operate on both eyes 1-2 weeks apart, but both eyes on the same day is sometimes performed if deemed the best thing for your needs and can be standard practice for some surgeons.

We aim to make the process as smooth and calm as possible. You’ll be given an arrival time and then an estimated operation time. We usually allow 40 minutes for the check-in, consent and preparation process. During this time you’ll be one-to-one with a nurse and have eye drops instilled to prepare your eye. You’ll be offered oral sedation (tablet) to calm the nerves. Many patients like this as it makes the operation feel easier.

During the operation, you’ll just experience a bright light, sensations or water around the eye and you’ll hear our theatre music. You don’t see any of the “work” happening. Some patients even see kaleidoscopic colours and patterns during surgery. When the operation is complete, you’ll sit up with a clear eye shield over the eye.

In my clinic, you’ll be offered a biscuit (chocolate chip is the best!) after the procedure and be given the do’s and don’ts before you head home.

Mr Dan Lindfield is a multi-award-winning consultant ophthalmologist and cataract surgeon in Guildford and Farnham. To make an appointment with him, head to his Top Doctors profile.