What Is Trivex?
Trivex (also marketed under the name NXT) is a urethane-based lens material introduced in 2001 by PPG Industries. It was designed to combine the best properties of CR-39 and polycarbonate: optical clarity, impact resistance, and ultralight weight. The name "Trivex" reflects its three key advantages (tri = three).
Key Properties
| Property | Trivex | vs. Polycarbonate | vs. CR-39 |
|---|---|---|---|
| Index of refraction | 1.532 | Slightly lower (thicker) | Higher (thinner) |
| Abbe value | 43-45 | Much better clarity | Lower clarity |
| Specific gravity | 1.11 | Lighter | Lighter |
| Impact resistance | Very high | Comparable (meets ANSI Z87.1) | Much better |
| UV protection | 100% inherent | Same | Better |
Advantages of Trivex
- Best overall balance: Combines good optics with excellent impact resistance
- Lightest ophthalmic material: Specific gravity of 1.11 makes it lighter than any other common lens material
- Better optics than polycarbonate: Abbe value of 43-45 vs. polycarbonate's 30 means significantly less chromatic aberration
- Impact resistant: Meets ANSI Z87.1 high-velocity and high-mass impact standards
- Inherent UV protection: Blocks 100% of UV without additional coating
- Excellent drill-mount performance: Ideal for rimless frames; does not crack at drill holes
- Stress-free optics: Cast (not injection molded), so no internal stress patterns visible under polarized light
Trivex is the LIGHTEST ophthalmic lens material (specific gravity 1.11) and has the best combination of optical clarity and impact resistance. It is often called the "premium alternative to polycarbonate" for patients who need impact protection but want better optical quality.
Limitations of Trivex
- Lower index than polycarbonate: At 1.532, Trivex lenses are slightly thicker than polycarbonate (1.586) for the same prescription
- Cost: Generally more expensive than CR-39 and polycarbonate
- Tinting: Does not accept conventional dyes as readily as CR-39; requires specialized tinting processes
- Not as thin as high-index: For prescriptions above ±4.00 D, high-index materials provide thinner profiles
When to Recommend Trivex
- Rimless (drill-mount) frames: Trivex is widely considered the best material for rimless due to its combination of flexibility, impact resistance, and lack of stress fractures at drill holes
- Patients sensitive to chromatic aberration: Upgrade from polycarbonate when the patient complains about color fringing
- Children and sports: When the patient or parent wants premium optics with impact protection
- Lightweight priority: For patients who find even polycarbonate or CR-39 too heavy
- Low-to-moderate prescriptions: Where the slight thickness difference from polycarbonate is not a concern
When a patient is currently in polycarbonate lenses and complains about visual quality (halos, color fringes, peripheral blur), upgrading to Trivex often resolves these issues. The Abbe value jump from 30 to 45 is significant and most patients notice the improvement. The lenses will be slightly thicker but lighter.
Telling patients that Trivex is "just like polycarbonate." While both are impact-resistant and UV-blocking, Trivex offers substantially better optical clarity (Abbe 45 vs. 30), lighter weight (SG 1.11 vs. 1.20), and no internal stress patterns. It is a genuinely different and superior material for optical quality.
Key Takeaways
- Trivex (n=1.532, Abbe 43-45) combines optical clarity, impact resistance, and ultralight weight
- Lightest ophthalmic lens material (specific gravity 1.11)
- Better optics than polycarbonate but slightly thicker
- Ideal for rimless frames, children, sports, and optical quality-conscious patients
- 100% inherent UV protection