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Phakic intraocular lens (PIOL) is a special kind of intraocular lens that is implanted surgically into the eye to correct myopia (nearsightedness). They are called "phakic" because the eye's natural lens is left untouched. This is in contrast to intraocular lenses that are implanted into eyes after the eye's natural lens has been removed during cataract surgery. Phakic intraocular lenses are indicated for patients with high refractive errors when the usual laser options for surgical correction (LASIK and PRK) are contraindicated.〔 Current Phakic IOLs are designed to correct high myopia ranging from -5 to -20 D if the patient has enough anterior chamber depth (ACD) of at least 3 mm. Three types of Phakic IOLs are currently available: * Angle-Supported * Iris-Fixated ==Indications== LASIK can correct myopia up to -12 to -14 D. The higher the intended correction the thinner and flatter the cornea will be post-operatively. For LASIK surgery, one has to preserve a safe residual stromal bed of at least 250 µm, preferably 300 µm. Beyond these limits there is an increased risk of developing corneal ectasia (i.e. corneal forward bulging) due to thin residual stromal bed which results in loss of visual quality. Due to the risk of higher order aberrations there is a current trend toward reducing the upper limits of LASIK and PRK to around -8 to -10 D.〔 Phakic intraocular lenses are contraindicated in patients who do not have a stable refraction for at least 6 months or are 21 years of age or younger. Preexisting eye disorders such as uveitis are another contraindication. Although PIOLs for hyperopia are being investigated, there is less enthusiasm for these lenses because the anterior chamber tends to be shallower than in myopic patients. Corneal endothelial cell count less than 2000-2500 cells/mm² is a relative contraindication for PIOL implantation.〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Phakic intraocular lens」の詳細全文を読む スポンサード リンク
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