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a progressively diminishing ability of the eye to focus, noticeable from middle to old age, caused by loss of elasticity of the crystalline lens
Collins Discovery Encyclopedia, 1st edition © HarperCollins Publishers 2005
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.



diminution of the power of accommodation of the eye due to advancing years. Presbyopia occurs as a result of sclerosing of the crystalline lens, which is unable to increase its curvature to the limit when there is a maximum tension (accommodation); the result is that its refractive power decreases, and the ability to see objects close to the eye is impaired.

Presbyopia begins at age 40 to 45 when eye refraction is normal. When myopia is present, it begins later, and with hyperopia, it comes on earlier. Treatment consists in appropriate selection of glasses for reading and close work. Persons 40 to 45 years of age with normal refraction need a plus lens of 1.0 to 1.5 diopters for reading at a distance of 33 cm. Every five years the refractive power of the lens is increased by 0.5 to 1 diopter. Corresponding corrections in the lens power are made for myopia and hyperopia.

The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.


Diminished ability to focus the eye on near objects due to gradual loss of elasticity of the crystalline lens with age.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
References in periodicals archive ?
Azarcon says studies have also shown that women are most likely to suffer premature presbyopia and begin to lose their eyes' focusing ability in their late 30s.
"We are able to do a contact lens that is uniquely able to fix (presbyopia) but, also, the contact lens is quite affordable in comparison to some of the current efforts made to fix this condition," Zapesochny said.
Dr Manal Taryam, CEO and Board member of Noor Dubai Foundation, explains that presbyopia occurs naturally as people age, making them unable to read small text at a distance, which can hinder daily activities such as reading text messages, books and subtitles on TV.
- Boston, Massachusetts-based presbyopia treatment developer Allotex has closed on financing from a strategic investor to fund its upcoming European clinical trials of its TransForm Corneal Allograft (TCA), the company said.
Nelson, "Review of the impact of presbyopia on quality of life in the developing and developed world," Acta Ophthalmologica, vol.
Presbyopia is caused by age-related elasticity changes in the crystalline lens and its capsule.
Simple reading glasses with convex lenses are used to correct presbyopia.
This condition is known as presbyopia. Signs that you may be affected by presbyopia include finding it difficult to focus, blurred vision at normal reading distance and eye fatigue along with headaches when carrying out close work.
Many people over 40 years old have difficulty focusing on close-up objects, a condition called presbyopia. Traditional lens designs, such as bifocal, trifocal, and progressive lenses--with sections for both long-range and near-range distances-can provide a solution.
According to Susan Hanson, chief operating officer of TRP Co., two conditions affecting ears and eyes offer rich opportunities for homeopathic products: tinnitus, or ringing of the ears, and presbyopia, blurred near vision.
Presbyopia, the difficulty most of us have as we age with focusing at nearby objects due to the hardening of the lens in the eye, can be a real problem with runners.
Summary: First Cataract & Refractive Femtosecond Laser and New Excimer Treatment for Presbyopia