Final answer:
Phakic intraocular lenses are used to correct myopia by adding the necessary power to focus light on the retina. They are not used for treating cataracts or glaucoma. Unlike LASIK, which reshapes the cornea, phakic IOLs are additional lenses implanted in the eye.
Step-by-step explanation:
Phakic Intraocular Lenses for Vision Correction
Phakic intraocular lenses (IOLs) are typically used to correct myopia, or nearsightedness. In this condition, images are focused in front of the retina rather than directly on it, usually because the eyeball is too long relative to the focusing power of the cornea and lens. The phakic IOL is implanted into the eye without removing the natural lens. It works by adding the necessary power to focus light correctly on the retina.
For a myopic person considering surgery like LASIK, the curvature of the cornea would be made smaller to decrease the eye's focusing power. In contrast, for hyperopia, or farsightedness, the cornea's curvature needs to be greater to increase the eye's focusing power. Astigmatism can also be treated with corrective lenses, but it involves irregularity in the cornea's curvature. Cataracts, which are treated by replacing the clouded lens with an artificial intraocular lens, are not corrected by phakic IOLs since in this case, the natural lens is removed due to the clouding.
Phakic IOLs are one surgical option among others like LASIK which reshapes the cornea directly, and neither treatment corrects glaucoma, which is an issue related to eye pressure and not merely vision focusing.