At checkout, the choice between standard and thinner lenses can be confusing. Quality Fast Specs offers options including 1.50, 1.56, 1.61, 1.67 and 1.74. A higher index can reduce thickness for the same prescription, but the best choice also depends on your frame, lens design and budget.
The same considerations apply whether you are buying new frames or reglazing a pair you already enjoy wearing.
Step 1: Read the full prescription
SPH (sphere) shows the main lens power. A minus value usually corrects short-sightedness; a plus value usually corrects long-sightedness. CYL and AXIS describe astigmatism. All of these values, as well as frame size and shape, affect the finished lens. Do not choose an index from SPH alone.
For many minus prescriptions, a smaller, well-centred frame can reduce visible edge thickness. For plus prescriptions, the frame can affect centre thickness. Ask for a recommendation based on the complete prescription and selected frame.
Step 2: Compare lens-index options
| Lens index | Typical role | What to check |
|---|---|---|
| 1.50 / 1.56 | Standard and mid-index options for many milder prescriptions | Check the exact included package and frame compatibility. |
| 1.61 | A thinner option often considered for moderate prescriptions | Compare thickness, price and available coatings. |
| 1.67 | A higher-index choice for stronger prescriptions or a slimmer look | Ask how much difference it makes in your chosen frame. |
| 1.74 | An ultra-high-index option for some strong prescriptions | Confirm availability, cost and suitability for the lens design. |
These are starting points, not fixed prescription cut-offs. Thickness and weight vary with lens power, shape, diameter and material. A higher index does not change your prescribed power or remove all visual effects of a strong prescription.
What if you have astigmatism?
Cylinder power can affect lens thickness in particular directions. Share the full SPH, CYL and AXIS values for both eyes so the optical team can assess the lens and frame together. A cylinder value alone does not dictate an index upgrade.
Step 3: Consider reglazing your existing frames
If your current frames fit well and remain in good condition, you may be able to replace only the lenses. The QFS reglaze service offers a free prepaid pack or shipping label. After assessing the frames, the team provides a personalised quote before proceeding.
Reglazing can help you keep a favourite pair of frames while updating the prescription or choosing a different lens type. The frame must be suitable for the work, so an assessment is part of the process.
Before you order
- Check which index and lens design suit your full prescription and chosen frame.
- Confirm which coatings are included with the specific package shown at checkout.
- If reglazing, ask whether your existing frame is suitable after assessment.
- Read the current returns and remake terms for the lenses you choose.
Explore frames at Quality Fast Specs
Learn about the QFS reglaze service
Frequently asked questions
Will a lower-index lens change my prescription?
No. Index does not change the prescribed power, but it can change thickness, weight and appearance. Ask the optical team to confirm lens and frame suitability.
Do higher-index lenses include anti-reflective coating?
Coating availability depends on the specific lens package. Check the options for your order or ask QFS to confirm before purchase.
How do I provide my pupillary distance?
Enter a reliable PD if you have one. If it is missing or unclear, ask which measurements are needed for your lens choice; multifocal lenses may need additional frame-specific measurements.
