What does my prescription mean?
Maybe you received your prescription and don’t understand what all the numbers mean. Our prescriptions are written in a standard form.
Spherical Power ~ Cylindrical Power ~ Axis ~ Add Power ~ Triangle/Prism
SPH: Spherical Power
A negative number in this column means you have Myopia - the image you are looking at is in focus in front of your macula (central vision). Essentially your eyeball is too long.
A positive number in this column means you have Hyperopia - the image you are looking at is in focus too far past your macula. Essentially your eyeball is too short.
Add: Add power
A number in this position is usually related to Presbyopia. This happens when the lens in the eye gets too rigid for the muscles that surround it to mold it into a shape to see up close. Generally this comes with age, resulting in the need for a bifocal (“add”) power. There are different ways to get that power in your lens
Lined bifocal - gives you two focal lengths ; distance and near
Lined Trifocal - gives you three focal lengths ; distance, intermediate, and near
Progressive lens - gives you any focal distance needed based on where you look through the lens
Cyl: Cylinder Power
A number in this position means you have Astigmatism. Instead of your cornea being completely spherical it is out-of-round. The image you are looking at is in focus in multiple places. This power in combination with the other power bring the images into focus directly at the macula. This means that the cyl power has to be at a certain orientation which is the axis number.
Prism
Numbers with an orientation in this column means that your eyes struggle to work together, often resulting in double vision. Either they move:
In - Exophoria, eyes position of rest is Outward
Out - Esophoria, eyes relaxed position is Inward
Down - Hyperphoria, eyes relaxed position is Up
Up - Hypophoria, eyes relaxed position is Down
Prism changes the direction in which light comes into the eye, decreasing/eliminating the double vision.