The majority of people who suffer from the symptoms of Computer Vision Syndrome  (CVS) - blurred vision, eyestrain and burning - are middle-aged and presbyopic.  Presbiopia is the inability to focus at all distances with symptoms including  squinting and headaches.
So, getting computer glasses can transform the  office environment for millions of workers at their workstations. As the glasses  correct the intermediate zone of your vision, which is the typical distance  (20-24") from your eye to the computer monitor screen, they enable the eye  muscles to move from keyboard to monitor and back more easily. This alleviates  the CVS symptoms of blurred vision and eyestrain.
Perhaps you are  sceptical of the need for specific computer glasses and consider them an  unnecessary expense: less emphasis has traditionally been placed on  computer-induced vision problems than on the ergonomic layout of the  workstation. Buying a pair of inexpensive, single-vision (intermediate) lenses  off the rack might, then, seem a good idea.
Unfortunately, as most  people who need computer glasses also need their vision corrected in the near,  and maybe far, zones as well, ready to wear, single-vision glasses don't usually  fit the bill. Nor do cheaper, tinted glasses help presbyopic individuals. The  pupil dilation, which results from reduced light entering the eye, can  exacerbate the problem of blurred vision and eyestrain.
Let's move now  from the cheapest, ready to wear, computer glasses to affordable, but more  expensive, eyewear with a greater degree of customization. Lenses can be  selected to match the requirements of each eye. This gives you a pair of bifocal  reading glasses with the upper area optimized for reading text on your monitor,  and the bifocal area set to allow the correct focal distance for the keyboard  and desktop.
Customization of the individual lenses, however, is  sometimes not enough to prevent 'prism' which occurs when your eye movements are  not perfectly synchronised. To overcome this problem, a choice of nose bridges  is often made available which realigns the distance between pupils and removes  this particular cause of eyestrain.
These "do-it-yourself" computer  glasses, which require you to find out your existing "add" prescription for each  eye, are stylish and lightweight. They also come with anti-reflective coatings.  Not only do these reduce the glare from ambient lighting in the workplace, which  adversely affects the eye's ability to focus clearly on the monitor, but they  also increase the scratch resistance of the lens.
The best possible  solution, of course, is computer glasses made to match the requirements of your  exact prescription and workplace setup. Fulfilling these requirements means a  visit to your eye doctor and a willingness to pay more for your eyewear. Seeking  professional help represents, for most people, the safest option.
The  more popular styles are the multifocals, particularly the progressive (no-line)  lenses. These have a larger intermediate zone than normal progressives and allow  you to see clearly in all zones (near, intermediate and far) at the same time  while at work.
However, in occupational progressive lens and lined  trifocals, there is a trade-off between a larger intermediate zone and distance  viewing. Both will allow you to see adequately in an office environment, but  they are not suitable for wear outside the office.
This problem of one  pair of glasses for normal use and a dedicated pair for computer use, can be  obviated by the use of clip-ons. Provided you are fortunate enough to need two  prescriptions only in your lenses (intermediate and near or intermediate and  far). You can wear your regular prescription lens in the glasses and the  computer lens in the clip.
Finally, there is a question of tinted lenses  in computer glasses. Opinions seem to vary on their use in reducing excessive  "blue light" spectrum. As we have seen, an ultraviolet coating can filter out  much of the blue light which reaches the eye from harsh fluorescent lighting. 
The jury seems to be out, though, when it comes to amber-tinted computer  glasses. Many sportsmen use them to cut down glare from a bright sun, but, in  the workplace, their use is not always thought to be beneficial. Some people  believe the resulting cut in light transmission and the concomitant increase in  use of the eyes focusing muscles, can aggrevate the very condition - eyestrain -  which the tint is supposed to alleviate.
Choose your computer glasses  wisely, but if your blurred vision continues, look at your work habits and  evaluate whether your working environment is ergonomically sound.
2008年9月9日星期二
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