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presbyopia پیرچشمی

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Presbyopia usually occurs beginning at around age 40, when people experience blurred near vision when reading, sewing or working at the computer.

When people develop presbyopia, they find they need to hold books, magazines, newspapers, menus and other reading materials at arm’s length in order to focus properly. When they perform near work, such as embroidery or handwriting, they may develop headaches, eye strain or feel fatigued.

Presbyopia is caused by an age-related process. This differs from astigmatism, nearsightedness and farsightedness, which are related to the shape of the eyeball and are caused by genetic and environmental factors. Presbyopia generally is believed to stem from a gradual thickening and loss of flexibility of the natural lens inside your eye.

These age-related changes occur within the proteins in the lens, making the lens harder and less elastic over time. Age-related changes also take place in the muscle fibers surrounding the lens. With less elasticity, the eye has a harder time focusing up close. Other, less popular theories exist as well.

Presbyopia Treatment

Eyeglasses

Eyeglasses with bifocal or progressive addition lenses (PALs) are the most common correction for presbyopia. Bifocal means two points of focus: the main part of the spectacle lens contains a prescription for distance vision, while the lower portion of the lens holds the stronger near prescription for close work.

Progressive addition lenses are similar to bifocal lenses, but they offer a more gradual visual transition between the two prescriptions, with no visible line between them.

Reading glasses are another choice. Unlike bifocals and PALs, which most people wear all day, reading glasses typically are worn just during close work.

Contact Lenses

Presbyopes also can opt for multifocal contact lenses, available in gas permeable or soft lens materials. Another type of contact lens correction for presbyopia is monovision, in which one eye wears a distance prescription, and the other wears a prescription for near vision. The brain learns to favor one eye or the other for different tasks. But while some people are delighted with this solution, others complain of reduced visual acuity and some loss of depth perception with monovision.

Surgery

Surgical options to treat presbyopia also are available. One example is Refractec Inc.’s conductive keratoplasty or NearVision CK treatment, which uses radio waves to create more curvature in the cornea for a higher “plus” prescription to improve near vision. The correction is temporary and diminishes over time. The procedure is performed on one eye only for a monovision correction.

LASIK also can be used to create monovision, in which one eye is corrected for near vision while the other eye is stronger for distance vision.

The Kamra inlay (AcuFocus), approved by the FDA in 2015, is surgically implanted just under the top layers of the cornea in one eye. It uses principles similar to how a camera works, controlling the amount of light entering your eye and increasing the range of what you see in focus.

PresbyLASIK is a new presbyopia-correcting surgery now undergoing U.S. clinical trials. This innovative procedure uses an excimer laser to create a multifocal ablation directly on the eye’s clear front surface (cornea). This enables vision at multiple distances.

A highly experimental treatment being studied is the injection of an elastic gel into the capsular bag, the structure in the eye that contains the natural lens. In theory, the gel would replace the natural lens and serve as a new, more elastic lens. Also, an elective procedure known as refractive lens exchange may enable you to replace your eye’s clear but inflexible natural lens with an artificial presbyopia-correcting lens for multifocal vision.

Reference

http://www.allaboutvision.com/conditions/presbyopia.htm

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