Ask the Optician

What effect will prism have in my glasses when I am not wearing them?


For some years I have used reading glasses, which are still fine for computer work (large screen on a desk). Most of my work is, however, done on a laptop, closer to me than a normal computer screen. I do not wear distance glasses.
Recently my eyes were tested. One optometrist gave me reading glasses which are fine for close reading but not good for working on my laptop.
I saw another optometrist, who has now suggested, after doing some tests, that I should have prisms in my glasses. I do not have them yet. The first optometrist told me that he could prescribe prisms, but he maintained that while they are great on, they have an effect on normal vision, once the glasses are off.
I am nervous about getting used to prisms in my glasses, only to have a negative effect on my day to day vision without them.
Please advise what effects wearing prisms for reading and/or closer work on a laptop screen is likely to have on my vision when my glasses are off.

Answer Written answer:

If it is just a small amount of prism it should make your vision more comfortable for close work, and have a minimal effect without them. A large degree of prism may make adapting when you take them off  difficult. I would guess that the amount of prism will be small so I do not think I would be too concerned. It is common with age to need a different prescription for intermediate use (like using a desk to top computer) then you need for close reading. A laptop is often a little inbetween. Sometimes for convenience you have to compromise in having a pair that that you can wear for both and adjust your working distances slightly. This saves you having too many pairs of glasses!

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Optician's Biography

Simon Kay BSc(Hons) MCOptom has been a qualified Optometrist for over 35 years, and has a vast experience of almost all aspects of optometry. He joined Specsavers Opticians in 1993 first in Liverpool and for 15 years as a director of Lancaster and Morecambe. He served on many panels and committees whilst a director, including those responsible for IT design and professional advancement. He was regional chairman of the North West directors of Specsavers for over 12 years and as such was involved in almost all aspects of optometry on a business and professional level. He has been involved on the Local Optical Committee for many years and is currently Vice Chairman in his area.
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