When you require custom prescription lens services at Even Realities, to ensure you select the most suitable lenses, we have prepared a detailed explanation of the power range and index selection. Please choose the appropriate lens power and index based on your prescription.
Power Range Description
Even Realities supports the following power ranges for prescription lenses:
- Sphere (SPH): +12.00 to -12.00
- Cylinder (CYL): +4.00 to -4.00
- Addition (ADD): +0.50 to +4.00 Note: Customization for ADD is only supported by Even Retail store.
Important Notes:
- Please confirm your prescription powers fall within our supported range. Power outside this range may not be manufacturable.
- If you are unsure about anything, we recommend consulting your ophthalmologist or optometrist.
Calculating Your Spherical Equivalent (SE)
To help you better select the lens index, first calculate your Spherical Equivalent (SE) using the following formula:
Spherical Equivalent (SE) = Sphere (SPH) + ½ Cylinder (CYL)
Example:
If your Sphere (SPH) is -4.00D and your Cylinder (CYL) is -2.00D, then your SE is:
(-4.00 + ½ * (-2.00)) = -5.00D）
If you are unsure how to calculate this, please feel free to contact our Service Team; we will be happy to assist you.
Index Selection Guide
Choosing the right index based on your Spherical Equivalent power can result in thinner and more comfortable lenses. Please refer to the table below for guidance:
Index Selection Reference Table:
Myopia (-) Power Range |
Recommended Index |
Hyperopia (+) Power Range |
Recommended Index |
< -3.00D |
1.60 |
< +2.00D |
1.60 |
< -6.00D |
1.67 |
< +4.00D |
1.67 |
> -6.00D |
1.74 |
> +4.00D |
1.74 |
Index Characteristics:
- Index 1.60: Suitable for medium powers, offering a thin profile and economic value.
- Index 1.67: Suitable for high prescriptions, thinner and lighter.
- Index 1.74: Suitable for very high myopia or hyperopia, ultra-thin and premium.
Selection Advice: If your Spherical Equivalent power is greater than +4.00D or less than -6.00D, selecting Index 1.74 is recommended to ensure optimal thinness and wearing comfort.
Frequently Asked Questions
Q: What if the two eyes have significantly different prescriptions? How should I choose the refractive index for the lenses?
A: When there is a significant difference in prescription between the two eyes, it is common practice to choose the refractive index primarily based on the eye with the higher prescription. This recommendation is made from an overall consideration of lens thinness, aesthetics, your personal visual habits, and the size of the frame.
Q: What if my prescription power is outside the ranges mentioned above?
A: If your prescription falls outside our supported range, we recommend consulting a professional ophthalmologist for further assessment.
Q: How do I know which lens type is suitable for me?
A: You can select the appropriate index based on your calculated Spherical Equivalent power. If you still have questions, our Service Team can provide personalized advice.
If the information above does not resolve your query, please contact our Service Team.