Intraocular lenses (IOLs) are permanent, plastic lenses that are surgically implanted to replace or supplement the eye’s natural crystalline lens. They have been used in United States since the late 1960s to restore vision to cataract patients, and more recently are being used in several types of refractive eye surgery.
It is possible to implant a lens in the eye without removing the natural lens. A flexible lens is inserted through extremely small incisions in front of the natural lens to correct nearsightedness or farsightedness. Once in the eye, the lens expands to its full size, allowing the eye to remain relatively untraumatized, thus reducing astigmatism and recovery time.
A Phakic intraocular lens (PIOL) is a lens implanted inside the eye for the correction of either extreme nearsightedness or extreme farsightedness. In effect, the lens becomes an internal contact lens rather than a contact lens on the surface of the eye. It is usually recommended for patients whose visual correction is outside the range that can safely be treated with LASIK.
Types of PIOLs:
Phakic IOLS (PIOLs) can be either spheric or toric-the latter is used for astigmatic eyes. The difference is that toric PIOLs have to be inserted in a specific angle, or the astigmatism will not be fully corrected, or it can even get worse. According to placement site in the eyes PIOLs can be divided into:
Angle supported PIOLs: those IOLs are placed in the anterior chamber. They are notorious for their negative impact on the corneal endothelial lining, which is vital for maintaining a healthy dry cornea.
Iris supported PIOLs: this type is gaining more and more popularity. The IOL is attached by claws to the mid peripheral iris by a technique called enclavation. It is believed to have a lesser effect on corneal endothelium.
Sulcus supported PIOLs: these IOLS are placed in the posterior chamber in front of the natural crystalline lens. They have special vaulting so as not to be in contact with the normal lens. The main complications with this type is their tendency to cause cataracts and/or pigment dispersion.
