Somewhere in the checkout process for a new pair of glasses, you’ll hit a lens material choice, and polycarbonate and CR-39 are the two options that come up most often as the standard, non-premium picks. They’re both perfectly legitimate choices, but they’re built for genuinely different priorities – one leans toward impact resistance and safety, the other toward optical clarity and cost. Neither is a strictly “better” material; the right one depends on what you actually need.
Quick version: CR-39 offers excellent optical clarity at a lower cost but is heavier and less impact-resistant. Polycarbonate is significantly more impact-resistant and lighter, making it the standard recommendation for children, sports use, and safety eyewear, though its optical clarity is slightly lower than CR-39’s, particularly at the edges of stronger prescriptions.
Table of Contents
- What CR-39 Actually Is
- What Polycarbonate Actually Is
- Optical Clarity Compared
- Impact Resistance Compared
- Weight and Thickness Compared
- Cost Compared
- Who Should Choose Which
- Comparison Table
- Buying Guide
- Common Mistakes
- FAQs
- Final Verdict
- References
What CR-39 Actually Is
CR-39 is a plastic lens material that’s been the standard in eyewear for decades, valued primarily for its excellent optical clarity and relatively low cost compared to premium materials. It’s a solid, reliable default option, particularly for people without a specific need for extra impact resistance or minimal thickness.
What Polycarbonate Actually Is
Polycarbonate is a thermoplastic material originally developed for uses requiring high impact resistance, including aerospace and safety equipment applications, before becoming a standard option in eyewear. It’s notably more resistant to shattering or cracking under impact than CR-39, and it’s also lighter, which is part of why it’s frequently recommended for children’s glasses, sports eyewear, and safety glasses.
Optical Clarity Compared
CR-39 generally offers slightly better optical clarity than polycarbonate, with fewer instances of chromatic aberration (a slight rainbow-like distortion sometimes visible at the edges of a lens, particularly in stronger prescriptions). This difference is often subtle enough that many wearers don’t notice it in daily use, but it can become more apparent for people with strong prescriptions or those who are particularly sensitive to visual distortion at the lens periphery.
Impact Resistance Compared
This is polycarbonate’s clearest advantage. It’s dramatically more resistant to shattering or cracking under impact than CR-39, which is why it’s the standard recommendation for children (who are naturally harder on glasses), athletes, and anyone working in an environment where eye protection from impact is a genuine safety consideration. CR-39, while durable enough for typical daily wear, doesn’t offer the same level of impact protection.
Weight and Thickness Compared
Polycarbonate is lighter than CR-39 at equivalent lens thickness, which can make a noticeable difference in comfort, particularly for larger frames or stronger prescriptions where lens size and thickness both increase. Polycarbonate also has a higher refractive index than CR-39, meaning it can be manufactured thinner for the same prescription strength, which is part of why it’s often recommended for stronger prescriptions in addition to its impact resistance benefits.
Cost Compared
CR-39 is generally the more affordable option of the two, making it a reasonable default for people without a specific need for polycarbonate’s impact resistance or reduced thickness. Polycarbonate typically costs somewhat more, reflecting its added durability and the more specialized manufacturing process involved.
Who Should Choose Which
Choose polycarbonate if: you’re buying glasses for a child, need safety or sports eyewear, have a stronger prescription and want reduced thickness and weight, or simply prioritize durability and impact resistance over marginal optical clarity gains.
Choose CR-39 if: you want the clearest possible optical quality, your prescription is mild enough that thickness isn’t a significant concern, budget is a primary consideration, and you don’t have a specific need for enhanced impact resistance.
Comparison Table
| Factor | CR-39 | Polycarbonate |
|---|---|---|
| Optical clarity | Slightly better | Slightly lower, minor distortion possible |
| Impact resistance | Moderate | High |
| Weight | Heavier | Lighter |
| Thickness at same prescription | Thicker | Thinner |
| Cost | Lower | Higher |
| Best for | Budget-conscious, mild prescriptions | Children, sports, safety, strong prescriptions |
Buying Guide
- Consider who will wear the glasses – children and active individuals generally benefit more from polycarbonate’s impact resistance.
- Factor in prescription strength – stronger prescriptions benefit from polycarbonate’s thinner, lighter profile.
- Weigh optical clarity priorities – if you’re particularly sensitive to lens distortion, CR-39’s slight clarity edge may matter more to you.
- Consider your budget – CR-39 is generally the more affordable standard option.
- Ask your optical provider for a direct comparison using your specific prescription, since the practical difference varies by individual prescription strength.
Common Mistakes
Choosing CR-39 for a child’s glasses purely to save money, without factoring in the significantly higher impact resistance polycarbonate offers for an active, growing child. Assuming polycarbonate’s optical clarity difference is always noticeable, when for many prescriptions the difference is genuinely subtle in daily use. Not considering polycarbonate for a strong prescription, resulting in unnecessarily thick and heavy lenses. And assuming either material is universally “better,” when the right choice genuinely depends on individual priorities and circumstances.
Is polycarbonate better than CR-39?
Neither is universally better – polycarbonate offers superior impact resistance and reduced weight, while CR-39 offers slightly better optical clarity and lower cost.
Which lens material is more scratch resistant?
Neither CR-39 nor polycarbonate is inherently highly scratch-resistant on its own; both typically require a scratch-resistant coating for meaningful protection, which is standard practice for both materials.
Do polycarbonate lenses distort vision?
Polycarbonate can show slightly more chromatic aberration at lens edges compared to CR-39, though this is often subtle and not noticeable for many prescriptions and wearers.
What lens material is best for children?
Polycarbonate is the standard recommendation for children’s glasses, given its significantly higher impact resistance for an active, growing child.
Is polycarbonate more expensive than CR-39?
Generally yes, reflecting its added durability and more specialized manufacturing process.
Which material is lighter?
Polycarbonate is lighter than CR-39 at equivalent lens thickness, and it can also be manufactured thinner for the same prescription strength.
Should I choose polycarbonate for sports or safety glasses?
Yes, polycarbonate is the standard recommendation for sports and safety eyewear given its high impact resistance.
Is CR-39 a good choice for a mild prescription?
Yes, CR-39 works well for mild to moderate prescriptions where thickness isn’t a major concern, and its optical clarity is excellent.
Does polycarbonate come with UV protection built in?
Polycarbonate naturally blocks a significant portion of UV light due to its material properties, though it’s still worth confirming full UV protection specifications with your specific lenses.
Can I get polycarbonate lenses for a strong prescription to reduce thickness?
Yes, this is one of the more common reasons to choose polycarbonate, since its higher refractive index allows for thinner lenses than CR-39 at the same prescription strength.
Final Verdict
CR-39 and polycarbonate are both solid, well-established lens materials suited to different priorities – CR-39 for optical clarity and cost, polycarbonate for impact resistance, reduced weight, and thinner lenses at stronger prescriptions. For children, athletes, and anyone with safety concerns, polycarbonate is generally the more sensible default. For everyone else, the choice comes down to how much you value the marginal optical clarity difference against the cost savings CR-39 offers
This article is for informational purposes only and does not constitute medical advice. Please consult a qualified eye care professional for personalised guidance.
We strive to keep our content accurate and up to date, but information may change over time. Please verify important details with official sources or eye care professionals.
