How to calculate the thickness of your lenses
How to Determine the Thickness of Your Lenses
As an experienced optician, I frequently encounter patients with concerns about the thickness of their eyeglass lenses—a common and understandable inquiry. The thickness of lenses is influenced by several variables, including the strength of your prescription, the sign preceding your corrections, pupillary distance, and your chosen frame. Before delving into the intricacies, let's establish what we mean by "lens thickness."
In simple terms, lens thickness refers to the depth or slenderness of your glasses lenses. Opting for standard lenses with a high prescription can result in a visibly thicker appearance. Through my optical practice, I've observed firsthand how lens thickness impacts visual acuity, comfort, and the overall aesthetics of eyeglasses.
Choosing the Right Glasses
The refractive index is a pivotal factor determining lens thickness, ranging from 1.5 to 1.74, with 1.5 being the most common and 1.74 the highest available index.
Here are general guidelines applicable in most cases:
- Power between 0 and 2: Index 1.5 is recommended.
- Power between 2 and 4: Index 1.6 is recommended.
- Power between 4 and 6: Index 1.67 is recommended.
- Power above 6: Index 1.74 is recommended.
To determine your power, sum the sphere and the cylinder (if the cylinder has the same positive or negative sign as the sphere), and add the ADD (addition) if the sphere is positive.
For example:
- Sphere -2 / Cylinder -1.5: Power 3.5
- Sphere +2 / Cylinder -1.5: Power 2
- Sphere +2 / Cylinder -1.5 / ADD +1.5: Power 3.5
- Sphere -2 / Cylinder -1.5 / ADD +1.5: Power 2
Frame selection is also crucial. The provided guidelines assume a lens width between 51 and 54. For larger frames, consider moving up one step in the recommendation. Conversely, for frames with a lens width under 51, move down one step. A larger lens width generally results in thicker lenses for the same index.
Calculating Lens Thickness
For a rough estimate of your lens thickness post-purchase, use this online calculator tool Calculating the thickness of my glasses.
When you are on the tool, please select the following equivalents from the Lens Material Type drop-down menu:
- Index 1.5: "Hard Resin"
- Index 1.6: "1.6 MR8"
- Index 1.67: "1.67 MR7"
- Index 1.74: "1.74 MR174"
If you don't know you PD, please enter the standard PD of 32 per eye, that should provide you with a good estimate.
Click on the following link to open the tool :
Calculating the thickness of my glasses
In conclusion, understanding lens thickness is crucial when buying eyeglasses online. Keep in mind that obtaining an exact preview is challenging due to the interplay of various factors. Your purchase experience matters to us, and we aim for transparency in guiding you through these considerations.
