They are the option most commonly used for younger people who have a high spectacle prescription and are out of range for laser eye surgery.

They are also preferred to refractive lens exchange in younger patients because the natural lens is still flexible enough to allow you to read without glasses after correction of your distance vision.

PIOLs may also be preferred to laser eye surgery in patients with medical dry eye conditions and keratoconus. The intraocular collamer lens (ICL) is a commonly used type of PIOL.

ICLs are soft, flexible implants which are similar to contact lenses, but they are implanted within the eye, and sit between the natural lens and the iris. You cannot see or feel the ICL after implantation, and they do not need to be cleaned.

Another type of PIOL, which sits just in front of the iris (the Artisan IOL) is also commonly used. Each of these lenses has advantages and your consultant will explain the best option for you after assessing your eyes.

PIOL surgery is normally performed under local anaesthetic and takes about 15 minutes. Surgery is not painful, recovery is relatively quick, and the aftercare is simple. You can normally go back to work the day after surgery.

Most surgeons prefer to leave one week between each eye for PIOL implantation, but you can wear a contact lens in the unoperated eye to help you work in the week between right and left eye surgery.

In all forms of eye surgery, problems can occur during the operation or afterwards in the healing period. Problems can result in permanent, serious loss of vision (vision worse than the driving standard in the affected eye that cannot be corrected with glasses or contact lenses). More commonly, problems can be corrected with changes in medication or additional surgery. Typically, these additional operations feel like the original surgery and have a similar recovery period.

Different types of PIOL have different associated risks. Your surgeon will ensure that you are given clear advice relevant to the lens type that is recommended.

Loss of vision

Permanent, serious loss of vision is very uncommon after ICL implantation. Causes include damage to the nerve at the back of the eye caused by a sudden rise in fluid pressure within the eye after surgery, and damage to the retina caused by infection or retinal detachment. Sudden pressure rises are much less common with the newer v4c ICL used for treating myopic patients. The v4c ICL allows natural fluid flow through the pupil and does not require a bypass drainage hole in the iris. If pressure rises do still occur, it is normally because of incomplete removal of supporting gel – a problem that can be fixed relatively easily with further washout. All patients with high levels of short sight have a higher risk of retinal detachment. This risk is not increased by ICL implantation, which does not involve surgery to the back compartment of the eye. Infection rates after ICL implantation are very low (approximately 1 in 6000). Complete loss of vision can occur after any operation involving the inside of the eye; but this is rare after ICL implantation.

Although fluid pressure rises and infection can occur after Artisan/Verysise PIOL implantation, the risk of problems leading to visual loss generally relates to later complications, particularly corneal clouding. These problems can often be spotted at an early stage and may be partially or completely intercepted by PIOL removal.

Annual review with your eye surgeon for life is normally recommended after Artisan/Verysise PIOL implantation, whereas a standard optometric eye health check once a year is sufficient after ICL implantation for which the main long-term risk is cataract formation.

Additional surgery

Cataracts may occur earlier in life than they would have done otherwise after all types of PIOL implantation. Cataract surgery can normally be combined with PIOL removal if necessary, and substitution of a new lens implant during cataract surgery helps to minimize any additional requirement for glasses. In other words, PIOL implantation does not stop you having successful cataract surgery or RLE later in life if this is required.

Statistical techniques are used to size ICL implants. The size prediction is sometimes incorrect, and in approximately 1 case in 40, the ICL needs to be replaced with a lens of a different size in order to get the best fit in the eye. A minor rotation of the position of an ICL implant is also sometimes required after surgery to optimise the correction of astigmatism. For Artisan/Verysise PIOLs, sizing is not a problem, since once size fits all. But repositioning procedures are sometimes required after the initial implantation.

PIOLs can be removed if they are causing problems. This usually means that your vision and eye health will be the same as it was before PIOL implantation. But not all problems caused by PIOLs can be corrected by removing them, and additional treatment may be required even after PIOL removal.

ICL removal is uncommon unless you require cataract surgery or an ICL of a different size.

Artesan/Verysise PIOLs are sometimes removed to prevent further deterioration in the eye health if it looks like the risk of corneal clouding is increasing or if there are persistent problems with eye inflammation.

For further information please refer to the Phakic Intraocular Lens Implantation leaflet developed by The Royal College of Ophthalmologists.

For more information, read our blogs:

• Unsuitable for laser eye surgery? Implantable contact lenses may be the answer
• Vision correction surgery when laser is not the right option - RLE & PIOLs