الفهرس 
Refractive ErrorsOnly 14 pages are availabe for public view
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Abstract
Refractive error correction has become a long standing debate, from the traditional use of spectacles and contact lenses to the era of LASIK. An alternative for the refractive errors’ management is the phakic IOL. Phakic intraocular implants overcome the disadvantages of corneal refractive surgeries and have been shown to correct successfully ametropia.
Phakic IOLs are considered an attractive approach, based in large part on the phenomenal acceptance of IOLs for not only the aphakic or cataract patient but also the refractive patient. The use of phakic IOLs offers the predictability and efficacy of IOL technology, yet is less invasive because the crystalline lens is left intact. In addition, the procedure is reversible /exchangeable, and if the crystalline lens is damaged during phakic IOL implantation, lensectomy with IOL implantation remains a good second option.
The Implantable Collamer Lens (ICL) is another type of Phakic Intraocular Lens which is manufactured from a soft foldable polymeric material called Collamer. The cornea is actually comprised of collagen and so this material provides excellent biocompatibility and superior optical capability.
The ICL offers a non corneal option for refractive correction. Current versions of the ICL are available between -3.00 and -20.00 diopters (D) and +1.50 to +20.00 D.A toric model, which corrects up to 6 D of astigmatism, is available. The ICL’s extended range of correction offers a compelling alternative for patients outside the accepted range of laser in-situ keratomileusis (LASIK).
It is readily implanted behind the iris by gently folding it and injecting into the anterior chamber through a tiny incision only 3.0mm in length placed by the surgeon at the clear edge of the cornea.
ICL implantation induces few halos possibly because it maintains the shape of the cornea, regardless of the amount of myopic correction.
The incidence of cataract with the ICL has varied from 2-3%. Several mechanisms have been put forward to explain cataract formation. Trauma to the crystalline lens during the implantation procedure is one of them. Metabolic disturbances induced by the implant also may be partially responsible for cataract formation. More attention is paid to proper sizing of the PC Phakic IOL, to achieve a big enough space between the IOL and the crystalline lens to leave the lens undisturbed.
The treatment of cataract in patients implanted with posterior chamber phakic IOLs is not difficult. Explantation of the ICL is easily performed through the same incision. Phacoemulsification and posterior chamber IOL implantation can be done in a routine fashion.
Patients who receive posterior chamber phakic IOLs are more likely to develop glaucoma than those with anterior chamber lens. Several mechanisms are available for increased intraocular pressure in these patients. In general, phakic IOL surgery leads to a slight and transient increase of the IOP during the first months after surgery and then the IOP returns to preoperative baseline.
Although endothelial cell loss is a major concern with anterior chamber IOLs, it does not seem to represent such an important problem with posterior chamber phakic IOLs.
The ICL proved to be comparable or, in some cases, superior to the corneal refractive procedures.The ICL offers the moderate to highly myopic patient a viable alternative to corneal laser refractive surgery.
The implantable contact lens offers an alternative approach to the management of pseudophakic anisometropia that avoids some of the risks associated with IOL exchange, corneal refractive surgery, and conventional piggyback IOLs.