Phakic Intraocular Lenses
When a patient is under 45 years of age but cannot have laser vision correction, an intraocular lens can be implanted without removing the natural lens and thereby losing the eye’s accommodation. These are called phakic lenses and are placed in behind the iris in the posterior chamber.
The Staar Visian ICL is a flexible phakic lens that is implanted behind the iris just in front of the natural lens. It can be used for moderate to high myopia and hyperopia and can come with astigmatism correction incorporated. These lenses have a long history. The major requirement is to size the lens correctly a task that cannot always be done precisely.
If too long the lenses vault forward and may require replacement if they cause chafing of the iris. If too short they sit too close to the lens with the risk in the long term of cataract formation. It is now possible to determine when a lens is too close to the natural lens by using a Pentacam, well before cataract develops and replace it with a longer lens. Regular checks are therefore essential.
The benefits of phakic lenses in patients with high refractive errors include superior predictability of outcome, generally superior visual contrast compared to laser vision correction for such errors and reversibility. Laser vision correction can also be combined with phakic implants should small refractive errors remain or develop.
Phakic lens implantation, unlike refractive lens exchange, is not linked directly to a higher risk of retinal detachment in myopic patients. Intraocular infection is also extremely unlikely. An increased potential for glaucoma needs to be considered when assessing suitability for these implants. As these implants are planned for younger patients, the long term safety also needs to be considered since these lenses have not been used for more than 20 years and life expectancy is considerably longer for these patients.