If you have a strong prescription, you've probably been told your lenses will be thick. High-index lenses are the solution — they're thinner, lighter, and more comfortable than standard lenses, without compromising on optical quality. But what exactly are they, and do you need them?
What Does "Index" Mean?
The refractive index of a lens material refers to how efficiently it bends light. A higher index means the material bends light more effectively, so less material is needed to achieve the same optical correction. In practical terms: a higher index = a thinner lens.
Standard plastic lenses have an index of 1.5. High-index lenses start at 1.6 and go up to 1.74 or even 1.9 for the very thinnest options available.
Common Lens Index Options
- 1.5 (Standard) — Suitable for mild prescriptions. The most affordable option.
- 1.6 (Thin) — Around 20% thinner than standard. Good for moderate prescriptions.
- 1.67 (Extra Thin) — Around 30% thinner than standard. Recommended for stronger prescriptions.
- 1.74 (Ultra Thin) — The thinnest widely available option. Ideal for very strong prescriptions.
Who Needs High-Index Lenses?
High-index lenses are particularly beneficial if:
- Your prescription is stronger than ±4.00 dioptres (sphere) or has significant cylinder correction
- You want thinner, lighter lenses for comfort and aesthetics
- You're choosing rimless or semi-rimless frames, where lens thickness is more visible
- You've previously found standard lenses too heavy or uncomfortable
If your prescription is mild (under ±2.00), standard 1.5 index lenses will likely be perfectly fine and represent the best value.
The Benefits of High-Index Lenses
Thinner appearance: High-index lenses reduce the "bottle glass" effect that can occur with strong prescriptions in standard lenses. This is particularly noticeable at the edges of the lens.
Lighter weight: Thinner lenses mean less material, which means less weight on your nose and ears. This makes a real difference in comfort, especially if you wear your glasses all day.
Better aesthetics: Thinner lenses look better in virtually any frame style, and open up more frame options for people with strong prescriptions.
Do High-Index Lenses Have Any Downsides?
High-index lenses do reflect slightly more light than standard lenses, which is why they're almost always paired with an anti-reflective (AR) coating. This coating eliminates the extra reflections and is strongly recommended — most high-index lenses include it as standard. They're also more expensive than standard lenses, but the improvement in comfort and appearance is significant for those with stronger prescriptions.
High-Index Lenses for Reglazing
If you're reglazing your existing frames, high-index lenses are an excellent upgrade — especially if your previous lenses were thick or heavy. You can choose your preferred index when ordering, and our lab will cut the lenses to fit your frames precisely.
Browse our Single Vision Lens Options or Varifocal Lens Options to see the index choices available for your prescription type.
Which Index Should You Choose?
As a general guide: if your prescription is under ±2.00, standard 1.5 is fine. Between ±2.00 and ±4.00, consider 1.6. Above ±4.00, opt for 1.67 or 1.74 for the best results. Your optician's prescription will help you decide, and our team is always happy to advise.