High-index lenses may look thinner and sleeker, but does a higher refractive index always mean better vision?
When choosing prescription glasses, thinner lenses often seem like the better option, especially for those with stronger prescriptions. That’s where high-index lenses come in. High-index lens materials bend light more strongly, allowing the same prescription to be made with less thickness than conventional plastic lenses.
But here’s something many people don’t realise: Thinner lenses don’t necessarily mean better optical clarity.
The refractive index describes how strongly a lens material bends light. Generally, the higher the index, the thinner the lens can be.
Common lens indexes include:
However, lens thickness also depends on your prescription, frame size, shape and eye positioning.
Not necessarily. Different lens materials bend colours of light by slightly different amounts, a phenomenon known as chromatic dispersion. Some people may notice faint coloured fringes around high-contrast objects, especially when looking through the outer portions of their lenses. This effect is related to a lens material’s Abbe value, where a higher value generally means less colour dispersion, while a lower value indicates more.
Many high-index materials have lower Abbe values than standard plastic lenses. But does this mean high-index lenses cause blurry vision? Not necessarily. Most wearers can enjoy clear, comfortable vision with high-index lenses, although some may be more sensitive to colour fringing, particularly when looking away from the optical centre.
Optical clarity also depends on more than lens material alone. Lens design, accurate fitting and suitable coatings all contribute to visual comfort. For example, a good anti-reflective coating can reduce distracting reflections, particularly when driving at night or working under bright lights, although it cannot eliminate colour dispersion caused by the lens material itself. This is why choosing prescription lenses should involve more than simply comparing refractive index numbers.
High-index lenses may be beneficial if:
The highest refractive index isn’t always the most suitable choice.
Even between 1.67 and 1.74 lenses, the additional thickness reduction may be relatively small, depending on your prescription and frame.
Choosing the right lenses involves more than selecting the highest refractive index. The ideal option should balance lens thickness, optical performance, comfort and your everyday visual needs.
At Eye & Glasses Optometrist, our optometrists can help you explore suitable lens materials, designs and frame combinations based on your prescription and lifestyle.
Not sure whether you really need high-index lenses? Visit us for professional advice before making your choice. Because the best lenses aren’t always the thinnest. They’re the ones that work best for you.