Thought Bytes...
March 2002

Aging Eyes

I just bought my first pair of reading glasses!

I hear it all the time... "I didn't need glasses until I started working on the computer so much"... "it seems like everyone needs glasses these days"... "my eyes get so tired at the office".

Well folks, the reality is that we (as a population) are getting older. Our bodies are starting to fail us. Sure, we can exercise to keep our metabolic rate from slowing and packing on the pounds, keep moving to keep arthritis out of our joints and keep thinking and reading and talking to keep the brain working . But the natural aging of the eyes is something that we have very little control over.

Our eyes are seriously overworked. The only time they get to rest is when we are in deep sleep. Even when we are sleeping lightly and dreaming our eyes keep working - this is called Rapid Eye Movement or REM sleep. And when we focus on an object, computer screen, book or crafts for any period of time, the muscle fibres controlling the eye stay in a contracted or tight position. This tight position restricts the oxygen and nutrient supply to the muscles and prevents clearing of the byproducts of metabolism, such as carbon dioxide and lactic acid. It is a little like when you carry a bag of groceries home. By the time you get home, you have to peel your fingers off the handle. This is the way our eyes feel when we don't vary the distance to what we are focusing on. As we get older, the continuous use of they eye muscles means that they don't respond as quickly. Some of the more common concerns are:

Presbyopia - This is the clinical term for short arms. Loss of flexibility of the lens itself result in the comfortable reading distance shifting forward. Some people who were short sighted to begin with find that they can now read without their glasses. For the rest of us, we have to hold the material further from our eyes - or do as I did, and break down and buy reading glasses. Some people opt for bifocals, trifocal and progressive lenses and I will discuss your options below. Choosing the wrong lenses could result in significant neck and upper back pain as you try to adjust your head to find the right point to see through for the task.

Glare sensitivity - The changes to the lens combined with less transparent internal structures means that light sources in our peripheral vision cause more glare because light scatters more. This is one reason why driving at night is more difficult - a couple of other issues in night vision include smoking and a decrease in pupil size. You are trying to focus on the road, but the peripheral lights from on-coming cars are more distracting (almost blinding). In the office, it is important to make sure that you cannot directly see any light sources. This may mean angling task lamps or turning out ceiling light fixtures. If you can see the light source, your automatic reaction will be to tilt your head to reduce the glare in your eyes.

Colour differentiation - Although it doesn't dramatically affect us during our occupational years, there is a slight yellowing of the lens over time. This is more pronounced in smokers and under incandescent light, which has a slight yellow tint. I really noticed this when I went to visit my late Grandmother several years ago. I was wearing faded jeans and a light blue shirt. She commented on what a lovely shade of green I was wearing (blue mixed with yellow makes green). The next day, wearing virtually the same clothes but we were outdoors, she noted that I had the same outfit in blue!

Of course, as we continue to get older, there are other very serious issues around the aging eye. Because I am not an optometrist, I will not go into any detail about cataracts (clouding of the lens), glaucoma (loss of peripheral vision) or macular degeneration (loss of central vision). These are issues you should discuss with your eye care professional.

The most notable problem by far is the change in your focal distance. Selecting the right lens is critical to your postural comfort. So, here are some of your options:

• Reading glasses - These are single vision lenses set for reading or screen distance. For touch typers, these seem to be the best option. You may still need bifocals though to interact with the rest of the world.
• Bifocals - When wearing bifocals, you have two options for your monitor. Either lower the screen and bring it closer or raise it and push it away. Some people will order a larger bifocal reading segment in the lens so that the screen does not have to be lowered as much. If the screen is at the wrong height you will probably find yourself working with your nose in the air, trying to see through the lower portion. This will definitely result in neck pain and headaches. Computer bifocals - These have the upper portion set for screen distance and the lower portion set for keyboard distance. Computer bifocals are excellent for the "hunt & peck" typers who must continually change their focus from the hands to the screen.
• Trifocals - Glasses with three distinct sections typically have a middle section set at about half the power of the reading segment. Most of the time this appropriate to looking on a shelf or at something slightly in excess of 1 metre away. Sometimes this works for the computer screen, but not often. My optometrist tells me that tri-focals are not appropriate until the lens of the eye has finished it's natural age related changes - i.e. has very little pliability left in it. Of course, you can let your optometrist know your exact screen distance and he/she will set that part of the lens accordingly.
• Progressive - Although more appealing to look at, progressive lenses often result in workers nodding the head up and down to find the right spot to look through. By their nature, progressive lenses have an infinite number of focal points gradually shortening as the eye's gaze moves down the central part of the lens. Particularly when the monitor is close, workers have to change head position to see from top to bottom of the screen. Unfortunately, this shift in lens power is controllable with good optics through a narrow corridor only. Things to the side and below eye level appear distorted. The greater the difference between the distance prescription and the near prescription, (i.e the more birthday candles you have in excess of about 40) the greater the peripheral distortion. As a result, this is a good lens for those who have copy to the side of their computer since they will have to turn their head and look directly at the copy and then turn their head again to look at the screen. (As noted, they will also tend to tilt their head back to see the screen.) Progressives are fine for lap tops though because the screen is below eye level and usually centred in front of the body.

Some people have to try several incarnations of their lenses before they find the kind they like. To help your optometrist set your lenses, have someone take a picture of you working at your computer. The picture should be from the side, taken at the same level as you. Write on the back the distance from your nose to the screen, the documents and the keyboard (if you frequently look at it). This will help the optometrist identify the angles and distances for the lenses. As a minimum, measuring the distance from your eye to the screen, the keyboard, and the work surface will give your optometrist a much better chance of providing an accurate prescription for work than if you guess at your working distances after you arrive at the clinic.

Article reviewed by:
Dr. Scott Brisbin
Lifetime Eyecare
780-420-2020
Suite 101, 6302 - 28 Avenue
Edmonton, AB
T6L 6K3

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