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how to calculate your eye prescription?

0 votes

How can I calculate my prescription for computer glasses?
The only formulas I can find online are for longsighted people. My near vision is perfect. For example, my prescription is:

Right  SPH -1.50, CYL -1.00, AXIS 85
Left SPH -1.25, CYL -1.00, AXIS 90

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asked Feb 12, 2017 in Health by smyadmin

5 Answers

0 votes
The nice thing about the optics of the eye is that the formulas are the same for everyone:

1/D = f

Where D is your lens power in diopters
And f is the focal distance in meters

So if you want your computer screen 80 cm from your face that is 0.8 m

1/D = 0.8
1/0.8 = D
D = 1.25 = +1.25

Now just add this +1.25 to the spherical portion of your prescription (for both eyes) and voilà you have computer glasses.

Note: this is just an example, different people like different distances and will need different prescriptions. Also this assumes that your distance prescription has not changed. Also it is important to get regular eye check ups from your optometrist or ophthalmologist to check for other eye diseases that may or may not have any symptoms. This answer is not a substitute for professional medical advice, please consult your medical professional for your own healthcare needs.
answered Feb 12, 2017 by Mitul Mehta
0 votes
You simply can't.  To do it properly there is too many factors involved.  Age, amount of accomodation left, symptoms, screen position, office layout etc. Power will have to be reduced for closework  but amount of reduction needed must be measured first. Besides there a lot of different type of lenses available for computer use and you well advised to get advice on which one would fulfill your needs first. Cheapest or simplest solution not always the wisest.
answered Feb 12, 2017 by Sergey Bobyk
0 votes
If you are over age of 40 measure the distance from where you sit from your eyes to the computer screen and then go to a pharmacy and try on reading glasses trying to read a newspaper at the same distance - the one that works best is your prescription.

Otherwise go and see an eye care professional.
answered Feb 12, 2017 by Mounir Bashour
0 votes
If you are under 40 years old, you can properly use your prescription for all distance

above 40 it will depend on your need for reading strength.

Reading is at about 40 cm, computer is at 80 cm to 1m so your computer “strength” for glasses would usually be half of what you need for reading

If this doesn’t help you contact me personally and i will help you more.


Emmanuel A.
answered Feb 12, 2017 by Oren Isaac
0 votes
To put in the simplest way, you need to have been prescribed an Rx from your eye doctor with an add power. This presbyopic prescription is then converted for a mid length prescription. For a computer screen, or arms length distance, you would generally use half of the add power prescribed on your Rx for the computer glasses.

An example of an Rx written might be:

O.D.= SPH-1.00 CYL-0.50 AXIS 90 ADD +2.00

O.S.= SPH-1.25 CYL-0.25 AXIS 75 ADD +2.00

You would then take half of the add power +2.00, which would be +1.00, and then add it to the SPH (or Sphere) of the prescription.

The add power is generally calculated for a distance of 12 to 18 inches for reading. half of that power would be for approximately 24 to 36 inches of reading distance (about the average distance of a computer monitor) that prescription would look something like this:

O.D= SPH -1.00 + 1.00 (HALF OF ADD)= 0.00

O.S.= SPH -1.25 + 1.00 (HALF OF ADD)= -0.25

The prescription then would be:

O.D.= SPH 0.00 CYL-0.50 AXIS 90

O.S.= SPH -0.25 CYL-0.25 AXIS 75

The best way is to ask your eye doctor for a separate computer glass prescription to be written, but you could just give your normal prescription to an eyeglass shop and say that you want computer glasses. they will use this same basic way of estimating your prescription.
answered Feb 12, 2017 by Scott Bird

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