Selecting Lenses

Rule of Thumb
Golden Rule

Rule of Thumb

By trying out a pair of drug store reading glasses you can come close to what is required for computer use. IF a pair of +1.25 Diopter glasses work with you for reading a book (12 to 16” away) then choose +.75 diopters for computer work!

IF a pair of +1.00 diopter work for reading a book, then choose +.50 Diopters for viewing a computer monitor!

WARNING: If astigmatism is more than 0.50 diopter, YOU NEED CUSTOM LENSES.

Click here to order online



PD: Interpupillary Distance. The distance between the pupils of your eyes measured in Millimeters. Average man is about 62mm. A friend can measure with a ruler marked in millimeters or do it while looking in a mirror. You should focus at a distance not close up.(PD is required to properly center lenses over pupils)

OD: Ocular Dexter or Right Eye

OS: Ocular Sinister or Left Eye

Diopter: A measurement of the refractive power of a lens.

Sphere: On your prescription this measures the degree of correction in plus or minus diopters

Cylinder: This refers to the degree of astigmatism in your eye. It has a diopter strength AND a number of degrees to show the location of the astigmatism in the visual field. WARNING: IF Cylinder is higher than .5 diopters you should have custom lenses made for you!

“ADD”: to prescriptions refers to the strength in Diopters that has to be added (on top
of your existing prescription in order to permit viewing things close up!
Always a + or positive diopter number. (Usually calculated at 16” for reading)

Myopic: Nearsighted, needs glasses with a – minus Rx to see well at a distance

Hyperopic: Farsighted, sees well at distance but requires + positive Rx to see things close up.

Presbyopic: From around 35 years of age the eye starts to loose it’s ability to focus on close up objects. (Slower for myopic individuals) You may still see well at a distance but require + positive Rx lenses (reading glasses) for close up work.


Golden Rule

Too strong a positive diopter adjustment will not permit clear focus at the distance of a computer monitor but too weak will not give as much relief from eye fatigue.

Conclusion: It is better to have too small a positive diopter correction than too strong since you can always move back a little further (usually only inches)! Since these lenses are made in .25 Diopter increments you should always choose the closest LOWER strength of lens.


Click here to order online


Your Cart