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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 It might be outdated or ideologically biased.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 ?
Specialists in presbyopic, or intraocular, lens surgery describe aspects of the procedure for other ophthalmologists.
Those who are farsighted and prematurely presbyopic (in their late 30s) may indeed be candidates for this procedure but not most aviators.
While the demands presbyopic baby boomers are putting on vendors to deliver reading glasses with an up-to-the-minute look are helping to lift reading glasses sales, it is the age group's sheer numbers and the fact that one's eyes deteriorate after a certain age that have led to record sales over the past few years.
Larger type sizes aid both the visually impaired and presbyopic baby boomers.
They are not used to treat people who have trouble seeing near objects--those who are farsighted--or people who need reading glasses as a result of the aging process--those who are presbyopic.
Research on the effects on visual resolution of this correcting strategy for presbyopia has been limited in range of "add" powers and to a presbyopic population.
It is also important to note that this patient is not presbyopic. When viewing a distant target in the primary gaze position, the patient will be looking through the optical centres (OC) (see Figure I) and will experience no unwanted differential prism.
Despite the latest approaches utilizing modern technologies, LASIK has its own limitations like irreversibility and an impact on optical performance.4 As far as clear lens exchange is concerned, it can be offered to presbyopic patients but is not appropriate for younger patients due to their intact accommodation reflex.
The introduction of MF IOLs (multifocal intraocular lenses) as a refractive tool in ocular surgery has been determined by the aim to provide a good vision from near to intermediate distances (considering the reading of papers or electronic devices) making presbyopic patients spectacle independent.
You can add terrain shading under the aero data, turn off private airports or airspace lines or increase the size of labels for presbyopic eyes.
Typically, the peripheral vision is affected first, so that the patient may be asymptomatic until late in the disease or non-specific symptoms like headache and frequent changes of presbyopic correction, reduced visual acuity.(1,2)