Guide to Lens Coatings & Materials

For those who appreciate the science behind the style, this guide explores the technical excellence at the heart of every JOIUSS™ lens. We believe that superior vision is a combination of the perfect frame and the most advanced lens technology available.

Here, we explain the specific properties of our lens materials, the benefits of choosing the right lens index for your prescription, and the advanced surfacing techniques we use to deliver a thinner, lighter, and clearer result. We also detail the essential coatings that we include as standard on every pair of glasses we make.

Lens Materials & Index: The Secret to Thinner, Lighter Lenses

The “index” of a lens, or “refractive index,” is a number that describes how efficiently the material bends light. The higher the index number, the more efficiently it bends light, which means less material is needed to achieve the same prescription power. The result is a lens that is significantly thinner and lighter than a standard lens.

At JOIUSS, we offer a complete range of lens indexes to suit every prescription, from the mildest to the most complex.

Automated Lens Index Selection

Feature Material Best For Key Benefits
1.50 CR-39 Low Prescriptions (up to +/- 2.50) The optical industry standard. Excellent clarity and value.
1.60 High-Index Medium Prescriptions (+/- 2.25 to +/- 4.00) Up to 20% thinner than standard 1.50 lenses.
1.67 High-Index Strong Prescriptions (+/- 4.25 to +/- 6.00) Up to 30% thinner than standard 1.50 lenses.
1.74 High-Index Very Strong Prescriptions (above +/- 6.00) The thinnest and lightest lens material available, up to 40% thinner than standard 1.50.

Advanced Surfacing: Aspherisation & Minimum Diameter

Beyond the material itself, the way a lens is shaped, or “surfaced,” has a profound impact on its performance and appearance. At JOIUSS, we utilize two advanced surfacing techniques to optimize every lens for its specific frame and prescription.

Aspheric Design

Traditional lenses have a spherical front surface, like a slice taken from a ball. This can cause visual distortions, especially at the edges of the lens, and can create a “bug-eye” effect with stronger positive prescriptions. Aspheric lenses, by contrast, have a more complex, non-spherical front surface that gradually flattens from the center to the edge. This sophisticated design provides:

• Sharper Vision: Edge-to-edge clarity with significantly less distortion.

• A Better Look: A slimmer, more attractive lens profile that reduces magnification of the wearer’s eyes.

Minimum Diameter Surfacing

For customers with positive (+) prescriptions, particularly in larger vintage-inspired frames, we employ minimum diameter surfacing. This process calculates the smallest possible lens blank required to fit the chosen frame, which dramatically reduces the center thickness and overall weight of the final lens. It is a highly technical step that most online retailers skip, but it is essential for achieving the best possible cosmetic result in a stylish, larger frame.

The JOIUSS™ Difference: By combining high-index materials with aspheric design and minimum diameter surfacing, we can create lenses for strong prescriptions that are cosmetically elegant, optically superior, and comfortable to wear all day, even in a statement-making frame.

Lens Coatings: Protection as Standard

Many brands treat essential lens coatings as expensive add-ons. We believe they are fundamental to good vision and durability. That’s why every single pair of JOIUSS™ clear lens comes with these two premium coatings as standard, at no extra charge.

• Anti-Reflection (Anti-Glare): This multi-layer coating eliminates distracting reflections from the front and back surfaces of your lenses. This not only reduces eye strain, especially when driving at night or working on a computer, but it also makes your lenses appear almost invisible, so people see your eyes, not your glasses.

• Anti-Scratch: A durable hard coat is applied to protect your lenses from the minor scratches and scuffs of daily wear, ensuring your vision remains clear and extending the life of your glasses.

* Tinted, Polarised or Transitions® are supplied with the anti-scratch coating as standard.

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Lens coatings & materials

Frequently Asked Questions

How do I know which lens index I need?

Our expert opticians will automatically select the most appropriate lens index for you based on your prescription, ensuring the best balance of thinness, lightness, and value. For very strong prescriptions, we will always recommend a 1.67 or 1.74 high-index lens.

Are all high-index lenses the same?

No. The quality of the material and the precision of the surfacing make a significant difference. Our high-index lenses are sourced from the world’s leading manufacturers and are surfaced using the latest digital technology to ensure maximum clarity and minimal distortion.

Why are my lenses still thick even with a high index?

For very strong negative (-) prescriptions, the edge thickness is the primary concern. For very strong positive (+) prescriptions, the center thickness is the concern. While high-index materials make a huge difference, the size and shape of the frame also play a role. Our use of aspheric design and minimum diameter surfacing are specifically designed to minimize this thickness, but a very strong prescription in a very large frame will always have more substance than a mild prescription in a small frame.