When it's time to get some visual correction for computer use*, it's worth your while to be aware of some of the issues involved… these are the things that are going through your optometrists' mind in finalising the best possible glasses for computer work for you.
* N.B. if you're still in denial and you want to do anything but wear glasses for the computer we will tackle this in an upcoming post...
For the under 40s (roughly)
Most of the time correcting your vision for the long distance will be sufficient for use at the computer. Occasionally an occupational lens will be used, that gradually puts a little bit more strength into the lower part of your lens.
For the (roughly) 40s+
Once you're in the age range for reading glasses, there's a bit more to getting glasses made for computer use.
- The strength you need for seeing the screen clearly may be different to what you need to see clearly across the room.
- The strength you need for seeing the screen clearly may be different to what you need to see close-up (eg reading a book or document).
- Both the distance of the screen from your eyes, and how high/low the screen is.
- The type of usage you have for computer work - which of the below is most you?
- I'm at the computer for long periods of time, just looking at the screen and nothing else
- I'm at the computer for long periods of time, looking at the screen but also reading documents/ other close work.
- I'm at the computer for long periods of time, looking at the screen, reading, and interacting - with people on the other side of my desk.
- I'm at the computer for long periods of time, but also have to be able to easily look across the room.
- I'm at the computer often, but also up and walking around, doing other things as well.
- Most of my work doesn't involve the computer, but I do need to use it from time to time.
- I use multiple monitors.
- Whether you want just one pair of glasses to do everything in your life, or whether you don't mind having a separate set of glasses just for your computer use.
It may look complex, but these are important factors in sorting out the best type/ design of lens. Often when people have problems with glasses prescribed for computer use, it's because the lens type and the nature of a person's computer usage are not well suited.
Here are the different lens types that can be prescribed for computer use: (all of the comments below are assuming the glasses are an up-to-date prescription).
1. Single focus reading glasses (usually set for about 40cm)
Whole lens has your reading focus.
Generally: great for reading | may be great/ may be OK for screen | may be OK for across the desk |often poor for across the room/walking
When you first start to need reading glasses, a simple set of readers will work well for the screen too. You'll probably find yourself taking your glasses off/ sliding them down your nose to see across the room though. Once you've needed reading glasses for a few years though, reading glasses will be a bit too strong for the computer distance, and you may find yourself leaning close to the screen.
2. Single focus VDU/screen glasses (usually set for about 70cm, or your measured screen distance)
Whole lens has your computer screen focus.
Generally: good to slightly weak for reading | great for the screen | may be OK for across the desk | may be poor for across the room/walking.
A pair of lenses set up just for the screen is ideal for people that look only at the screen. You'll find youself taking them off for walking around/ looking across the room, so not really ideal when your computer work is in an interactive setting.
3. Regular bifocal glasses (top half set for long distance, bottom part set for reading distance)
Generally: good for reading| uncomfortable for screen | OK for across the desk | OK for walking around in
Regular bifocals and computers don't generally get along very well. Watch most people with regular bifocals working at the computer, and you'll see them leaning forward, and bending their neck back, in order to get the screen in focus - not ideal for prolonged computer use. There are two bits 'wrong' with regular bifocals and screens - firstly the lower section is set for reading distance not screen distance (hence the leaning forwards), and secondly screens are usually higher in your line of sight than the bifocal section (hence bending the neck back).
If you have to use bifocals at a computer, set yourself up with the screen as close as useful, and as low as possible.
4. Custom VDU bifocals (top half set for screen distance, bottom part set for reading distance)
Generally: good for reading| great for screen | may be OK for across the desk | may be poor for across the room/walking.
Bifocals designed for use at the VDU work quite well for people who spend longer periods looking just at the screen, but need a little extra strength for their reading/ close up work. Because the top part of the lens is all set up for the screen, that bit works well, and the bifocal segment at the bottom gives good reading vision. They are great while you only need to be at the computer, but they aren't very good for looking across the room or walking around in.
5. Occupational/ 'extended near focus' lenses (a special-purpose progressive lens)
Generally: good for reading| good for screen | can be set to be good for across the desk | may be poor for across the room/walking | progressive lens, therefore some distortion to the sides.
The lens is set for reading at the bottom of the lens, gradually changing in strength higher in the lens, so that looking ahead can be set for either 'screen' or 'across the desk'. They are a type of progressive lens, so new wearers will often take some time to adapt to the varying strengths in the different parts of the lens. As a progressive design, they are optimized to give as wide a field of view as possible in the screen portion of the lens. The prescription in these can be varied to include good vision for the 'across the desk' distance. Often people can walk around the office OK in these once they are adjusted to them, but they wouldn't generally be prescribed for full-time wear.
Quite often these are prescribed to people who have previously just used reading glasses at the computer, if updating their reading glasses would make them too strong for comfortable screen use.
6. Regular progressive/multifocal lenses
Generally: good for reading and screen, but clear zone not as wide | good for across the desk | good for distance (once adjusted to progressive lenses) | progressive lens, therefore distortion to the sides.
The lens is set for reading at the bottom of the lens, gradually changing in strength higher in the lens, so that looking ahead is set for long distance/across the room. The screen distance will be found about mid way between 'straight ahead' and 'looking down through the bottom of your glasses'. Because there is quite a bit of lens strength change from top to bottom in the lens, it may take new wearers some time to get used to 'finding' the best part of the lens to use for computer work. In all progressive lenses, there is some distortion out to the sides, which affects the width of the clear zone. If having a wide zone of clear screen viewing is the most important thing - especially people working in creative/art, or with multiple screens, then you may want to look at one of the other options.
These lenses are ideal for people who need to wear glasses fulltime, and who come and go from the computer during the course of their work. The work quite well for people doing longer term computer work, as long as they are adjusted to the limitations of the clear zone in the lens. For people whose work is solely at the computer, and who don't mind having a set of glasses just for their computer work, one of the other options may give better performance.
There is quite a range in both design and quality in progressive lenses, and accurate lens centring is important. This involves an element of trust on your part, good ethics on the part of the person making the glasses, and careful fitting once you've chosen your frames. One good little litmus test - accurate lens centring can only be done once your chosen frames are fitted on you, so the level of carefulness that is taking in getting the frames sitting right on you first, before the lens centring measurements are taken, is a good indication of the level of care.
- Putting an anti-reflective coating on the lens reduces annoying reflections - as long as you keep the lenses clean.
- Choosing a glasses frame that is well-suited to 1) your strength of lens 2) the type/design of lens prescribed 3) your head, as well as 4) your sense of style.
- Optimizing the physical set-up for working at the computer - how far/close you sit, how high/low the screen is, getting things as comfortable as possible.
- Giving your eyes (and fingers) a little rest periodically.
- Looking out for 'dry eye' symptoms. Dry eye symptoms are more commonly reported in screen based work than traditional office work, for a number of reasons.
as you can see if you've reached this point, there are quite a number of different factors involved in getting the best possible computer correction for you, and coming to the best solution needs input from both you and your eye care practitioner. I've consciously put 'generally' or 'often' in what I've written as things vary from one person to another. But hopefully, by reading this, you'll have more of an idea of what to ask about, and what to report when you next get your eyes tested and admit that you may need some help to see the computer clearly.