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Eye Health

Although your eyes stop growing during early teenage years, the lenses in your eyes continue to grow and produce more and more cells each year. Over time, this continued growth causes the lens to harden, losing some of its elasticity and some focusing ability. The result is known as Presbyopia, a naturally occurring eye condition that affects many people after the age of 40.

The symptoms of Presbyopia include headaches and blurred vision due to the added strain of trying to read small print or perform tasks at close range.

Presbyopia (Greek word “presbyteros” (πρεσβύτερος), meaning “elder”) is the eye’s diminished ability to focus that occurs with aging. 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 leveling off at 0.5 to 1 dioptres 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. 

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. Principle of a pinhole camera. … In optics, a circle of confusion, (also known as disk of confusion, circle of indistinctness, blur circle, etc. …

A delayed onset of seeking correction for Presbyopia has been found among those with certain professions and those with miotic pupils.  In particular, farmers and housewives seek correction later, whereas service workers using computers and doing lots of reading and construction workers seek eyesight correction earlier.