Understanding Eyeglasses and Lenses

The last time you visited your eye doctor, did he or she explain your prescription to you? What about the type of vision correction you need? Were you given any kind of suggestion for what kind of lenses would work best with your prescription or were you left with an optician to make those decision for you? Chances are good that you were left in the dark and this is not uncommon. Many eye doctors will check your vision, hand you a copy of your prescription, and send you off to go purchase eyeglasses with a sales agent. Understanding your prescription is the first step to understanding your eyeglasses and lenses and the following information will guide you to purchasing the best glasses for your vision.

The first thing to understand is your prescription. Take a look at the top section – do you see the abbreviations SPH, CYL, and Axis? In short, your SPH stands for sphere and it’ll tell you what kind of distance correction you need. Your CYL stands for cylinder and this will tell you what kind of astigmatism correction you need – it works in conjunction with your Axis. If you don’t see any numbers under the CYL or Axis, it means one or both of your eyes does not have astigmatism! Your sphere will contain a number with a plus (+) or minus (-) sign. The plus sign tells you that you need magnification to correct your vision while a minus sign tells you need help seeing afar. The numbers may be whole numbers like -2.00 or may contain quarter incremental numbers like +4.25. It’s important to take a look at your prescription before you leave the doctor’s office to fully understand the numbers and symbols of the prescription. If you choose to order glasses online, it’ll help you in the ordering process.

Prescriptions with a plus sign will result in lenses that are thicker in the middle while prescriptions with a minus sign will have lenses that are thicker on the sides of the lens. Why is this important? It’s good to know where the thickness will lie when picking out lenses. If you’re opting for thinner lenses – your prescription will help indicate which high index lens would be best for you! If your prescription lies within the range of -2.00 to +2.00, you should be fine with the basic CR39 lens; a high index lens of 1.56 is typically 25 percent thinner than basic plastic lenses and can work with prescriptions ranging from -4.00 to +2.00; if your prescription ranges from -6.00 to +4.00, opt for the high index 1.61 lens that is 30-50 percent thinner than regular plastic lenses.

For high prescriptions like -8.00 to +4.00, high index 1.67 lenses are perfect but for prescriptions higher than this, like those that range -12.00 to +4.00, the thinnest lens you can get is 1.74 high index. It’s important to remember that the higher your prescription in plus or minus, the thicker your lenses will be – even with high index lenses. The thinner your lenses are, the more important it is for you to get a UV protective coating.

Once you fully understand what kind of eye glasses you need for your vision, the easier it will be for you to choose a set of lenses. Remember to take your eyeglasses prescription with you when you leave your doctor’s office and always ask questions before leaving!