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Refractive Errors

  • Prescriptions for glasses have two main components: shape and power. The shape of a lens determines the type of correction. Concave, or minus, spherical lenses are thicker at the sides than in the middle to correct nearsightedness (myopia). Convex, or plus, lenses are thicker in the middle than at the...

  • Prescriptions for glasses have two main components: shape and power. The shape of a lens determines the type of correction. Concave, or minus, spherical lenses are thicker at the sides than in the middle to correct nearsightedness (myopia). Convex, or plus, lenses are thicker in the middle than at the...

  • What is farsightedness? People who are farsighted see things at a distance more easily than they see things up close. If you are very farsighted, close objects may be so blurry that you can't do tasks such as reading or sewing. A farsighted eye sees things differently than an eye that is not farsighted. Farsightedness...

  • Photorefractive keratectomy (PRK) and laser epithelial keratomileusis (LASEK) for farsightedness use a laser to reshape the cornea so that light is refocused on the retina. The laser reshapes the cornea accurately without damaging nearby tissues. No surgical cut is needed. Either procedure may be used to correct...

  • Laser in-situ keratomileusis (LASIK) is the preferred procedure for correcting farsightedness (hyperopia). It changes the shape of the eye. In LASIK, a thin flap is made on the cornea using a blade or laser. The flap is lifted, and a laser is applied to the central corneal tissue. The laser makes contact with the cornea...

  • Corneal ring implants are clear pieces of plastic that can be surgically implanted into the clear, dome-shaped bulge at the front of the eye called the cornea. The implants flatten the cornea and reduce nearsightedness. The implants are shaped like crescents or half-circles. After you get local anesthesia, two implants...

  • Guides through decision to have laser surgery to correct nearsightedness. Covers benefits and risks. Discusses who is a good candidate for surgery. Includes interactive tool to help you make your decision.

  • Prescriptions for glasses have two main components: shape and power. The shape of a lens determines the type of correction. Concave, or minus, spherical lenses are thicker at the sides than in the middle to correct nearsightedness (myopia). Convex, or plus, lenses are thicker in the middle than at the...

  • PRK (photorefractive keratectomy), LASEK (laser epithelial keratomileusis), and epi-LASIK (epithelial laser in-situ keratomileusis) use a laser to reshape the cornea. By reshaping the cornea, these surgeries allow light to focus on the retina and thereby correct a person's vision. With PRK, the top layer on the...

  • LASIK (laser in-situ keratomileusis) is a surgery that flattens the cornea. It is the most common laser surgery for correcting nearsightedness (myopia) and astigmatism. LASIK makes a small flap in the cornea and removes some of the tissue exposed by the flap. The laser removes tissue from the cornea very accurately...

  • What is nearsightedness? Nearsightedness (myopia) is a common cause of blurred vision. It can be mild, moderate, or severe. If you are nearsighted, objects in the distance appear blurry and out of focus. You might squint or frown when trying to see distant objects clearly. View a photo as seen through a normal and a...

  • Bifocal contact lenses have been developed for people who have both nearsightedness and presbyopia. Bifocal lenses provide correction for both near and distance vision on each lens. A number of designs are available in hard and soft lenses. There are two main types of bifocal contact lenses: Segmented (also called...

  • Bifocal contact lenses have been developed for people who have both nearsightedness and presbyopia. Bifocal lenses provide correction for both near and distance vision on each lens. A number of designs are available in hard and soft lenses. There are two main types of bifocal contact lenses: Segmented (also called...

  • What is presbyopia? Presbyopia is the normal worsening of vision with age, especially near vision. As you approach middle age, the lenses in your eyes begin to thicken and lose their flexibility. The ability of the lens to bend allows our eyes to focus on objects at varying distances ( accommodation). The loss of this...

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