What Are Intraocular Lenses (IOLs) and When Are They Used?
Intraocular lenses – or IOLs – are an important product in the world of vision correction. In fact, they are vital in Cataract Surgery, which just happens to be the most commonly performed elective procedure in the UK. With over 400,000 cataract procedures performed by the NHS each year in England alone, you may well think (correctly) that IOLs are indispensable.
So, when you realise that IOLs are not only used in Cataract Surgery, it only becomes more clear just how instrumental these tiny little lenses really are in refractive surgery.
But what exactly are intraocular lenses?
We’re going to walk you through the different kinds of IOLs as well as when they are used and what they can do. So, let’s start at the beginning…
What are Intraocular Lenses?
IOLs, sometimes referred to as phakic IOLs, implantable lenses, intra-corneal lens implants, or by brand names such as Artisan® lenses and Prelex® lenses, are artificial lenses that are implanted in the eye.
In simple terms, IOLs work in the same way as contact lenses; however, they require no maintenance and remain permanently inside the patient’s eye – though they can be surgically removed, if necessary. Depending on the type of lens, IOLs can be fitted in a number of ways, as Dr Glenn Carp explains in the video below.
IOLs can be used to correct a much wider range of prescriptions when compared with other treatments such as Laser Eye Surgery. However, the type of lens used can depend on a number of factors.
When Are IOLs Used?
Different types of intraocular lenses, highlighted in the video above, are used in different procedures, including ICL Surgery, Cataract Surgery, and Clear Lens Exchange. So, what is the difference between these procedures?
Implantable Collamer Lens (ICL) Surgery is the most commonly performed type of Phakic Intraocular Lens Implantation. It is often considered an alternative treatment for patients who are not suitable for Laser Eye Surgery (usually because their prescription is too high).
The procedure involves implanting a small, thin lens behind the iris and in front of the natural lens of the eye. Modern ICLs can be used to correct almost every possible prescription. For example, in the UK the lens is available for short-sightedness from -0.50 to -18.00 D, long-sightedness from +0.50 D to +10.00 D and astigmatism up to 6.00 D.
In the video above, Mr Glenn Carp explains what intraocular lenses can treat.
Clear Lens Exchange (CLE)
Clear Lens Exchange (CLE) – also known as Refractive Lens Exchange (RLE) – also involves placing a type of IOL inside the eye. However, unlike ICL Surgery, CLE involves removing the eye’s natural lens and replacing it with an artificial one.
This artificial lens (which again, can be selected to correct almost any prescription) is placed inside the lens capsule behind the iris. Removing the natural lens in this way means that the eye’s natural ability to focus is removed.
For this reason, CLE is usually used in presbyopia patients and involves fitting one eye with an IOL designed for distance vision and the other eye with an IOL designed for near vision. The brain is then able to combine these two fields of vision to create a clear image at both distance and close-up. However, ICL Surgery is generally the preferred procedure for younger patients.
The most commonly performed elective procedure in the UK relies heavily upon IOLs. Cataract Surgery involves removing the cataract in order to restore vision. However, in doing so, the natural lens has to be removed as well. Like in Clear Lens Exchange, IOLs are implanted into the lens capsule to replace the natural lens.
In fact, Cataract Surgery and CLE are, in essence, the same procedure. Of course, the most significant difference is the condition of the natural lens being replaced. In CLE, correction of the refractive error is the primary focus. In contrast, the primary aim is to remove the cataract, with any possible refractive correction being secondary.
Types of IOLs
There are three types of IOLs: monofocal, multifocal, and toric. The type used in each of the surgeries above will depend on a number of factors, including where the treatment is carried out (private vs NHS), and your prescription.
Monofocal IOLs are the most common kind (Cataract Surgery provided by the NHS uses exclusively monofocal IOLs). They are designed to only focus on one field of vision (distance or near vision). Most procedures using monofocal IOLs will involve implanting a lens that focuses at a distance. Glasses can then be worn for near vision.
In comparison to monofocal lenses, multifocal IOLs are able to facilitate near, intermediate, and distance focus. As such, these types of IOLs can be specifically selected to correct a wide range of prescriptions, including long-sightedness (hyperopia), and short-sightedness (myopia).
Toric IOLs are the newest kind of intraocular lenses. They can help to eliminate refractive errors caused by corneal astigmatism. Before their introduction, patients with astigmatism who had Cataract Surgery had no option that would correct their astigmatism without the help of glasses or contact lenses.
A number of tests may be required to determine which lens is right for you – no matter which IOL procedure you require. Your surgeon will use a number of measurements to make an accurate recommendation on the best fit for your circumstances and prescription.