If you’re an eyeglasses or contact lens wearer, you may have heard of the term “diopter strength.” But what exactly does this term mean? In this post, we’ll explore what diopter strength is, how it’s measured, and how it impacts your vision.

Defining Diopter Strength

Diopter strength is a way to measure the power of a lens, whether it’s your eyes, glasses, or contact lenses. This number indicates a lens’ ability to bend light and focus it onto your retina (the light-sensitive layer at the back of your eye). 

A lens with a high diopter value has a strong ability to bend light — it’s thicker in the middle and thinner towards the edges. On the other hand, a lens with a lower diopter is thinner in the middle and thicker at the edges and generally has a weaker ability to bend light.

The diopter strength is used to prescribe corrective lenses for nearsightedness, farsightedness, astigmatism, and other types of eyewear like reading glasses.

How Diopter Strength Affects Your Vision

If you have a high diopter strength, your eyes can bend more light towards your retina, making objects clearer. On the other hand, if you have a lower diopter strength, your eyes are less efficient at bending light, making your vision blurry — this is where corrective lenses come in to help you compensate.

How Diopter Strength is Measured

During an eye exam, your optometrist may use a phoropter containing lenses of various diopter strengths. This tool determines which lens power gives you the sharpest vision. Your optometrist will likely have you look at a chart on the wall while they switch between filters and ask you to identify which option is clearest.

Once your diopter strength is determined, optometrists can prescribe eyeglasses or contact lenses. For example:

  • A diopter strength of +1.00 D indicates mild farsightedness. The higher the value, the worse the farsightedness. 
  • Negative diopters, like -1.00 D, indicate nearsightedness. The higher the absolute value, the more intense it is. 

Getting an eye exam is the best way to learn more about your natural diopter strength and the lenses that can best support your vision. At Laurier Optical, our optometrists have the tools and expertise to provide comprehensive assessments so you can better see the world around you. Contact us today to book an appointment.