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Standard Lenses (CR-39 / 1.50 Index)

Starting from$29

CR-39 plastic is the industry-standard lens material. Index 1.50 — the baseline for lens thickness comparisons. Best value for mild to moderate prescriptions.

What Is CR-39?

CR-39 (Columbia Resin #39) is a lightweight optical plastic developed in the 1940s. It remains the most widely used lens material for prescription eyeglasses due to its excellent optical clarity, low chromatic aberration, and affordability.

Refractive Index 1.50

The refractive index of a lens material determines how much it bends light per unit of thickness. CR-39 at 1.50 is the baseline — higher index numbers produce thinner lenses for the same prescription.

Advantages

  • Excellent optical clarity with minimal chromatic aberration
  • Lightweight — roughly half the weight of glass
  • Easy to tint
  • Most affordable lens material
  • Good scratch resistance with coating

Best For

CR-39 is ideal for prescriptions up to approximately ±2.50 sphere. Beyond that, the lens edges or center become noticeably thick, and upgrading to a higher-index material is recommended.

Common Questions

How do I know which lens index I need?
As a general guide: up to ±2.50 — CR-39 works fine. ±2.50–±4.00 — consider 1.60. ±4.00–±6.00 — 1.67 recommended. Above ±6.00 — 1.74 is ideal.
Does higher index mean better optical quality?
Not necessarily. CR-39 has the lowest chromatic aberration of all plastic materials. Higher index materials have slightly higher chromatic aberration, though most wearers don't notice it.
Are high-index lenses more fragile?
High-index lenses have higher clarity but are slightly more brittle than polycarbonate. For impact-prone situations (sports, children), polycarbonate's toughness outweighs the thinness benefit.

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