what is Presbyopia?

Answer 1

Presbyopia is the eye's diminished ability to focus that occurs with ageing.Presbyopia is not a disease as such, but a condition that affects everyone at a certain age.

first symptoms:
The first symptoms are usually noticed between the ages of 40-50, though in fact the ability to focus declines throughout life, from an accommodation of about 20 dioptres (ability to focus at 50 mm away) in a young person to 10 dioptres at 25 and levelling off at 0.5 to 1 dioptre at age 60 (ability to focus down to 1 -2 metres only). For those with good distance vision, it may start with difficulty reading fine print, particularly if the lighting is poor, or with eyestrain when reading for long periods.

Answer 2

Presbyopia is a condition in which the lens of the eye loses its ability to focus. The condition is associated with aging and is progressive (gets worse). People who have presbyopia have difficulty seeing objects close-up. Vision can be corrected with glasses or contact lenses. (MedlinePlus)
Presbyopia is loss of the lens' ability to change shape to focus on near objects due to aging. Typically, presbyopia becomes noticeable by the time a person reaches his 40s. A convex (plus) lens is used for correction when viewing near objects. These may be supplied as separate glasses or built into a lens as bifocals or variable focus lenses.(Merck)

Answer 3

This is age related loss of accomodation in the eye. Basically the eye's "auto focus" diminishes as objects get closer. This is caused by harding of the lens with age, the commonest cause of which is cataracts.
A person with presbyopia will focus well on distant objects but will tend to lose fucus as the objects get closer. That's why they tend to read stuff at arm's length.

Answer 4

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Answer 5

During middle age, usually beginning in the 40s, people experience blurred vision at near points, such as when reading, sewing or working at the computer. There's no getting around it — this happens to everyone at some point in life, even those who have never had a vision problem before.

Currently an estimated 90 million people in the United States either have presbyopia or will develop it by 2014. This is generating a huge demand for eyewear, contact lenses, and surgery that can help presbyopes deal with their failing near vision.

Presbyopia Symptoms and Signs
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 have headaches or eyestrain, or feel fatigued.

What Causes Presbyopia?
Presbyopia is caused by an age-related process. This is different from astigmatism, nearsightedness and farsightedness, which are related to the shape of the eyeball and caused by genetic factors, disease, or trauma. Presbyopia is generally believed to stem from a gradual loss of flexibility in the natural lens inside your eye
These age-related changes occur within the proteins in the lens, making the lens harder and less elastic with the years. 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: Eyewear
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 nearsightedness or farsightedness, 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 lines between them.

Reading glasses are another choice. Unlike bifocals and PALs, which most people wear all day, reading glasses are typically worn just during close work. If you wear contact lenses, your eye doctor can prescribe reading glasses that you wear while your contacts are in. You may purchase readers over-the-counter at a retail store, or you can get higher-quality versions prescribed by your eyecare practitioner
There are contact lenses for presbyopes, called multifocal contact lenses. You can obtain multifocal contact lenses 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 dizziness or nausea, or miss the depth perception they once had.

Because the human lens continues to change as you grow older, your presbyopic prescription will increase over time as well. You can expect your eyecare practitioner to prescribe a stronger correction for near work as you need it.

Presbyopia Treatment: Surgery
New surgical options to treat presbyopia are being researched and are already available in many countries. 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 method was FDA-approved for the temporary reduction of presbyopia in April 2004. (In 2002 it had been approved for mild farsightedness.) Read more about how CK works.

A highly experimental treatment is a soft, elastic polymer gel that researchers say would be injected into the capsular bag, the cavity that contains the natural lens. In theory, the gel would replace the natural lens and serve as a new, more elastic lens. Experiments also have centered on laser treatment of the eye's hardened lens to increase flexibility and improve focus.

Answer 6

Basically far-sightedness, like when you have trouble seeing things close-up and need bifocals. It usually occurs in aging people. Presby=old, opia=relating the eye.

Answer 7

Presbyopia = Elder vision....

Answer 8

Presbyopia (Greek word "presbyteros" (πρεσβύτερος), meaning "elder") is the eye's diminished ability to focus that occurs with ageing. The most widely held theory is that it arises from the loss of elasticity of the crystalline lens, although changes in the lens's curvature from continual growth and loss of power of the ciliary muscles (the muscles that bend and straighten the lens) have also been postulated as its cause.

Presbyopia is not a disease as such, but a condition that affects everyone at a certain age. The first symptoms are usually noticed between the ages of 40-50, though in fact the ability to focus declines throughout life, from an accommodation of about 20 dioptres (ability to focus at 50 mm away) in a young person to 10 dioptres at 25 and levelling off at 0.5 to 1 dioptre at age 60 (ability to focus down to 1 -2 metres only). For those with good distance vision, it may start with difficulty reading fine print, particularly if the lighting is poor, or with eyestrain when reading for long periods. Many advanced presbyopes complain that their arms have become "too short" to hold reading material at a comfortable distance.[1]

In optics, the closest point at which an object can be brought into focus by the eye is called the eye's near point. A standard near point distance of 25 cm is typically assumed in the design of optical instruments, and in characterizing optical devices such as magnifying glasses.

Presbyopia, like other focus defects, becomes much less noticeable in bright sunlight. This is not the result of any mysterious 'healing effect' but just the consequence of the iris closing to a pinhole, so that depth of focus, regardless of actual ability to focus, is greatly enhanced, as in a pinhole camera which produces images without any lens at all. Another way of putting this is to say that the circle of confusion, or blurredness of image, is reduced, without improving focusing.

A delayed onset of seeking correction for presbyopia has been found among those with certain professions and those with miotic pupils.[2] In particular, farmers and housewives seek correction later, whereas service workers and construction workers seek eyesight correction earlier.

Focusing mechanism of the eye
There is some confusion in articles and even textbooks over how the focusing mechanism of the eye actually works. In the classic book, 'Eye and Brain' by Gregory, for example, the lens is said to be suspended by a membrane, the 'zonula', which holds it under tension. The tension is released, by contraction of the cilliary muscle, to allow the lens to fatten, for close vision. This would seem to imply that the cilliary muscle, which is outside the zonula must be circumferential, contracting like a sphincter, to slacken the tension of the zonula pulling outwards on the lens. This is consistent with the fact that our eyes seem to be in the 'relaxed' state when focusing at infinity, and also explains why no amount of effort seems to enable a myopic person to see further away. Many texts, though, describe the 'ciliary muscles' (which seem more likely to be just elastic ligaments and not under any form of nervous control) as pulling the lens taut in order to focus at close range.[citation needed] This has the counterintuitive effect of steepening the lens centrally (increasing its power) and flattening peripherally.

Presbyopia and the 'payoff' for the nearsighted
Many people with myopia are able to read comfortably without eyeglasses or contact lenses. Myopes considering refractive surgery are advised that this may be an advantage after the age of 40 when the eyes become presbyopic and lose their ability to accommodate or change focus..


Treatment
Presbyopia is not routinely cureable, though tentative steps toward a possible cure suggest that this may not be impossible, but the loss of focusing ability can be compensated for by corrective lenses including eyeglasses or contact lenses. In subjects with other refractory problems, multifocal lenses (such as bifocal or trifocal lenses) or progressive lenses are used. In some cases, the addition of bifocals to an existing lens prescription is sufficient. As the ability to change focus worsens, the prescription needs to be changed accordingly.

Around the age of 65, the eyes have usually lost most of the elasticity. However, it will still be possible to read with the help of the appropriate prescription. Some may find it necessary to hold reading materials farther away, or require larger print and more light to read by. People who do not need glasses for distance vision may only need half glasses or reading glasses.

While bifocals and multifocals offer a working solution to everyday problems, they are hated by many, especially engineers, camera operators, and those used to having a good sharp distortion-free image in their work. Varifocals cause straight lines to look bent, and can leave some feeling dizzy after extended use. The power of simple, multiple prescriptions should not be underestimated. Reading glasses hastily prescribed may be fine for reading, but not good for shopping and generally walking around in. A slightly weaker prescription however, just powerful enough for reading using the full remaining accommodation of the eye, may feel much more comfortable for more general use too. Careful calculation of working ranges, together with a certain amount of trial and error, can restore undistorted vision for critical tasks for many people who do not find multifocals to their liking.

In order to reduce the need for bifocals or reading glasses, some people choose contact lenses to correct one eye for near and one eye for far with a method called "monovision". Monovision sometimes interferes with depth perception. There are also newer bifocal or multifocal contact lenses that attempt to correct both near and far vision with the same lens.


Surgery
New surgical procedures may also provide solutions for those who do not want to wear glasses or contacts, including the implantation of accommodative intraocular lenses (IOLs). Scleral expansion bands, which increase the space between the ciliary body and lens, have not been found to provide predictable or consistent results in the treatment of presbyopia.