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Give or take a week, something happens to human eyes when they reach the age of 43,5. It happens without warning and affects most normal eyes in Australia. Suddenly, people who have been able to read without glasses all their life find themselves struggling to see small print. They’ll be in the car and be unable to read the names in the street directory or they’ll be in a restaurant and have to concentrate hard to see what’s on the menu.

Instead of holding a book at a comfortable distance, they notice they are now holding it at arm’s length and even then are finding it hard to read. They are commonly heard asking for more light, and they find it especially hard to focus close up when they are tired: a tired body means tired eyes, which are too weary to take on the extra strain of reading small print.

The 40s is the spectacle decade. Most people who have avoided wearing glasses for reading now find themselves buying a pair off the shelf at the newsagent or booking themselves in for an eye test.

While this vision change is a perfectly natural part of the ageing process, some people can stave it off for a few years. Ultimately, however, it will happen to them too. Relaxed and rested on holiday, they might find they can read the morning newspaper on the beach without glasses, but once they get out of the bright light, it may not be so easy.

Some ophthalmologists say this phenomenon uncannily kicks in at 43,5. It’s called presbyopia, from the Latin for ‘old sight’, and is part of a process that usually begins in the third decade of life.

In this process the crystalline lens, which sits just behind the pupil in the eye, gradually becomes less flexible. This lens is responsible for adjusting the focus from a distant point to a near point. Tiny little muscles push and pull on this lens to adjust its curvature and make it refocus in a process known as accommodation.

Children have an excellent capacity for accommodation even if they are long-sighted. Their lenses are fluid and highly flexible and the muscles in their eyes are strong.

With age, the lens inevitably hardens and muscles eventually become fatigued. By the time a lens reaches its 40s, it is harder and muscles have to do extra work to make it accommodate, although it can still provide good distance vision.

People’s lenses continue to harden until they are in their late 60s. As hardening progresses, stronger and stronger glasses are required to compensate for it. By the age of 70, the process has stabilised as no more accommodation is possible.

In their 70s and 80s, some people experience what looks like a reversal in this process. They begin to realise they can read without their glasses. Often adult children remark on how odd it is that, after depending on spectacles for 25 to 30 years, their mother now has better sight and is able to sew and read without them. Unfortunately, this usually means the mother is developing cataracts that will eventually have to be removed.

Some eye doctors say one of the best measures of body ageing is the person’s ability to focus. By measuring how much focusing power is lost, they believe they can tell how well the person has aged.

If I have a 70-year-old patient who looks 60, I will try and treat them as if they were 60. Vision is linked to general health,’ says one ophthalmologist.

When they hit their 40s many people resist getting glasses in the incorrect belief that the glasses will make their eyes lazy and lead to further deterioration. While there is no reason to rush to get spectacles, there is little point delaying too long.

Eventually, they will need help with reading. There are alternatives for those who don’t want to wear glasses for personal reasons. While research into a laser option continues apace, there are the options of bifocal contact lenses and monovision.

Bifocal contact lenses are specially weighted at their base so they hold their position in the eye and are correctly placed for reading.

With monovision, vision is corrected in one eye only. Although they are usually unaware of it, most people have one dominant eye. To create monovision, the nondominant eye is identified, and a contact lens is placed on it to give it reading vision. This eye then becomes blurred for distance vision. The person then uses the dominant eye for general vision and getting about in the world and the nondominant eye for reading. The price for this is the loss of binocular vision, which can only occur when both eyes work together.

Some people can’t tolerate different vision in both eyes and some grow used to it and find it effective. Several well-known public figures who prefer not to wear glasses for vanity opt for monovision.

There are laser centres that will modify one eye to create monovision. Some eye specialists don’t push this option because they believe it is better to have both eyes set for normal vision.

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This entry was posted on Thursday, March 12th, 2009 at 12:38 pm and is filed under Men's Health-Erectile Dysfunction. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.