PIOLs

Phakic Intraocular lenses (PIOLs) are lenses that are surgically implanted into the eye to correct refractive errors. Phakic refers to the fact that the lens is implanted without removing the natural lens. The lenses, made up of plastic or silicone, are inserted just infront or just behind the iris (colored portion of the eye).

PIOLs act as an alternative to LASIK. In LASIK, tissue is removed using the excimer laser to alter the shape of the cornea; PIOLs, on the other hand, function like glasses or contact lenses. There are two phakic-IOLs that are FDA approved in the U.S: The Verisyse PIOL and the Vision ICL. Both lenses may improve a patient’s distance vision.

High Myopia
Patients who are poor candidates for laser correction may be candidates for phakic IOLs. Excimer lasers approved by the FDA can usually treat myopia of up to -12.00 to -14.00 diopters (D). Above these limits and in cases where the cornea is too thin or too flat for laser surgery, phakic IOLs become the major alternative. 

Most phakic IOLs for myopia can correct up to around -20 to -30 Diopters.
In September 2004, the FDA approved the first phakic IOL designed to correct high myopia. The Verisyse™ (AMO/Ophtec, USA Inc.), also known as Artisan/Worst “Iris-Claw” Lens, was approved for:

• Myopia ranging from -5.00 to -20.00 D

• Astigmatism less than or equal to 2.5 diopter 

• Adults 21 years of age or older with an ACD of 3.2 mm or greater and Shaffer grade II as determined by gonioscopy

  In December 2005, a second phakic IOL was approved by the FDA for the correction of high myopia.  The Visian ICL™ (Implantable Collamer Lens) is a posterior chamber phakic IOL approved for the correction of:

• Myopia ranging from -3 to -20 D

• With less than or equal to 2.5 diopter of astigmatism

• In adults 21-45 years of age with an ACD of 3.0 mm or greater and Shaffer grade II as determined by gonioscopy

High Hyperopia. The upper limits for hyperopic laser surgery are around +4.00 to +6.00 D. Higher attempted corrections can cause excessive steepening of the cornea. Phakic IOLs are available for the correction of hyperopia up to +3.00 D.

High Astigmatism. LASIK is the treatment of choice for astigmatism of up to 4.00 or 5.00 D. One should consider implanting toric phakic IOLs in cases of high degrees of astigmatism (usually above 5-6 D) whether associated with myopia or hyperopia.

Both spherical and cylindrical corrections are combined in these lenses, which aims to correct the total refractive error. High primary astigmatism can also be treated with relaxing procedures such as arcuate and transverse keratotomies, and with toric pseudophakic IOLs in cases where the crystalline lens is opaque.