Intraocular Lens - Intraocular Lenses For Correcting Refractive Errors

Intraocular Lenses For Correcting Refractive Errors

Intraocular lenses have been used since 1999 for correcting larger errors in myopic (near-sighted), hyperopic (far-sighted), and astigmatic eyes. This type of IOL is also called phakic intraocular lens (PIOL), and the crystalline lens is not removed.

More commonly, aphakic IOLs (that is, not PIOLs) are implanted via Clear Lens Extraction and Replacement (CLEAR) surgery. During CLEAR, the crystalline lens is extracted and an IOL replaces it in a process that is very similar to cataract surgery: both involve lens replacement, local anesthesia, both last approximately 30 minutes, and both require making a small incision in the eye for lens insertion. People recover from CLEAR surgery 1–7 days after the operation. During this time, they should avoid strenuous exercise or anything else that significantly raises blood pressure. They should also visit their ophthalmologists regularly for several months so as to monitor the IOL implants. CLEAR has a 90% success rate (risks include wound leakage, infection, inflammation, and astigmatism). CLEAR can only be performed on patients ages 40 and older. This is to ensure that eye growth, which disrupts IOL lenses, will not occur post-surgery.

Once implanted, IOL lenses have three major benefits. First, they are an alternative to LASIK, a form of eye surgery that does not work for people with serious vision problems. Effective IOL implants also entirely eliminate the need for glasses or contact lenses post-surgery for most patients. The cataract will not return, as the lens has been removed. The disadvantage is that the eye's ability to change focus (accommodate) has generally been reduced or eliminated, depending on the kind of lens implanted.

Two types of PIOLs have been approved by FDA. The VisianICL (Visian Implantable Collamer Lens), (FDA approved in 2004), produced by Staar Surgical Company and Artisan Myopia lens (FDA approved in 2004), produced by Ophtec USA Inc. The VisianICL is made of collamer, a biocompatible material, and the Artisan is a plastic lens.

Some of the risks that FDA have been found so far during a three-year study of the Artisan are:

• a yearly loss of 1.8% of the endothelial cells,
• 0.6% risk of retinal detachment,
• 0.6% risk of cataract (other studies have shown a risk of 0.5 – 1.0%), and
• 0.4% risk of corneal swelling.

Other risks include:

• 0.03 – 0.05% eye infection risk, which in worst case can lead to blindness. This risk exists in all eye surgery procedures, and is not unique for IOLs.
• glaucoma,
• astigmatism,
• remaining near or far sightedness,
• rotation of the lens inside the eye within one or two days after surgery.

One of the causes of the risks above is that the lens can rotate inside the eye, if the PIOL is too short if the eye was incorrectly measured, or because the sulcus has a slightly oval shape (the height is slightly smaller than the width).