How do I know my contact lense power?

How do I know my contact lense power?

You’ll find that the cylinder number on a contact lens prescription is always a minus number. This indicates the extra power you need for astigmatism correction. A higher number denotes a more severe level of astigmatism. The cylinder value for a glasses prescription on the other hand can be a plus or minus.

Do doctors check for contact lenses?

If you wear or want contacts, you need a contact lens exam in addition to a comprehensive eye exam. Your eye doctor will perform special tests during a contact lens exam to evaluate your vision with contacts. Your doctor may also do a tear film evaluation to make sure you have enough tears to comfortably wear contacts.

How do you calculate a prescription diopter?

For example, if your prescription is a sphere of -5.0 and a cylinder of +2.0, then (1/2 x +2.0) + -5.0 = -4.0 step diopter lens. Or if your prescription is a sphere: -2.0 and a cylinder: -1.0, then (1/2 x -1.0) + -2.0 = -2.0 (rounded up from -2.5) step diopter lens.

Do I need a separate eye test for contact lenses?

If you plan to wear contact lenses, you’ll need a separate eye exam because contact lenses are classified as medical devices. The good news is a contact lens exam can usually be performed at the same time as your comprehensive eye exam.

What does a contact lens exam consist of?

A contact lens exam will include both a comprehensive eye exam to check your overall eye health, your general vision prescription and then a contact lens consultation and measurement to determine the proper lens fit.

What does diopter count mean?

These numbers represent diopters, the unit used to measure the correction, or focusing power, of the lens your eye requires. Diopter is often abbreviated “D.” For example, if your prescription says -1.00, you have one diopter of nearsightedness. This is a fairly mild amount of nearsightedness.

Can you figure out your eye prescription online?

Thankfully, if you have a pretty basic prescription (meaning they’re not bifocals, progressives or Coke-bottle lenses), there’s a free tool from GlassesUSA.com that can scan your current glasses.

How many diopters of glasses prescription equal a contact lens prescription?

Any prescription over -3.50 to -4 diopter, and add +0.25 diopters for every two diopters of increase: So a -4.00 glasses prescription is roughly equal to a -3.75 contact lens prescription.

What size diopter lens do I need for my Lenses?

However, the difference between a +1.25 lens and a +1.50 (or +1.75 and +2.00) diopter lens is quite small. We recommend “rounding up” to the nearest +0.50 diopter. And – if you absolutely must have a +1.25 (or other +.25 increment) lens, then we will be happy to create a custom Prescription Monocle to meet your needs.

Why is the power of contact lenses less than glasses?

Therefore, in our example, the power of a contact lens will be less than the eyeglass prescription for the right eye. A GP lens automatically corrects the astigmatism of the surface of the cornea by molding it into a spherical shape. So a GP lens power will typically be close to the spherical correction of the glasses prescription.

How do you convert contact lenses to glasses?

Here’s how you convert contact lenses to glasses: Any prescription over -3.50 to -4 diopter, and add +0.25 diopters for every two diopters of increase: So a -4.00 glasses prescription is roughly equal to a -3.75 contact lens prescription. Here’s a handy chart: Some advise starting conversion at -3.50.