Lens Material Comparison: CR-39 vs Polycarbonate vs Trivex vs High-Index

Six ophthalmic lens materials dominate today’s dispensing floor, and choosing among them requires balancing index of refraction, Abbe value, specific gravity, impact resistance, and prescription range. The quick-reference table below captures every material in a single view.

Quick answer: For Rx between plano and ±3.00 D, CR-39 is the cost-effective default for optics; polycarbonate or Trivex is mandatory for safety, sports, and pediatric applications. For Rx above ±4.00 D, switch to mid-index 1.60 or high-index 1.67. For Rx above ±6.00 D, 1.74 delivers the best cosmetics, but expect Abbe 32 and visible chromatic fringing if the patient has cylinder or uses peripheral gaze heavily.

Quick-Reference: Lens Material Specifications

Sources: Laramy-K lens materials chart; Mitsui Chemicals MR Series; HOYA Polycarbonate vs Trivex technical guide; Optician Online — Properties of Lens Materials

A note on the impact standards: all prescription lenses sold in the US must pass the FDA 21 CFR 801.410 drop-ball test, which drops a 5/8-inch steel ball from 50 inches onto the lens center. ANSI Z87.1-2020 is a stricter occupational safety standard requiring a high-velocity impact test with a 1/4-inch steel ball at 102 mph; polycarbonate and Trivex both meet this higher threshold. CR-39 and the MR-series high-index materials do not.

The Six Lens Material Families

Ophthalmic lens materials fall into two broad chemical families: thermosets (CR-39, and the urethane-based high-index materials) and thermoplastics (polycarbonate). Trivex sits in a third category, a urethane-based material developed by PPG Industries that was originally engineered for military helicopter windshields before entering the optical market commercially in the early 2000s.

Understanding the chemistry matters because it explains the performance trade-offs. Thermosets cure into a fixed molecular network, which produces better optical uniformity (higher Abbe values) but limits impact resistance. Polycarbonate is a thermoplastic with exceptional impact resistance but a disordered molecular structure that scatters white light into its component wavelengths, producing the low Abbe value of 30 that defines its primary optical limitation.

CR-39: The Optical Benchmark

CR-39 (allyl diglycol carbonate, also called ADC or Columbia Resin 39) has an index of refraction of 1.498, a specific gravity of 1.32 g/cm³, and an Abbe value of 58. That Abbe value is the highest of any commonly dispensed plastic lens material, meaning it produces less chromatic aberration than any alternative at equivalent power.

For low-to-moderate prescriptions (roughly plano to ±4.00 D), CR-39 delivers the best optical clarity available in a plastic lens. The material also accepts tint uniformly, transmits color accurately, and is the easiest uncoated plastic to scratch-coat.

When to recommend CR-39: Low or moderate Rx in full-rim frames for patients who prioritize optical clarity and color accuracy, particularly artists, photographers, or anyone doing fine color-discrimination work. Budget-conscious patients with low Rx benefit because CR-39 is typically the lowest-cost option and requires no premium for optical performance at low powers.

When to avoid CR-39: Children and high-activity adults, patients needing drill-mount or rimless frames, patients with prescriptions above ±4.00 D (where lens edge/center thickness becomes clinically problematic), and any patient requiring certified safety eyewear. CR-39 does not meet ANSI Z87.1 high-velocity impact requirements.

Trivex: The Underrated Middle Ground

Trivex has a refractive index of 1.532 (commonly listed as 1.53), a specific gravity of 1.11 g/cm³, and an Abbe value of 43–44. No other lens material combines those three properties: it is the lightest standard ophthalmic material available, passes ANSI Z87.1-2020 high-velocity impact testing, and delivers an Abbe value 47% higher than polycarbonate.

Trivex is lighter than polycarbonate (specific gravity 1.11 vs 1.20), despite offering equivalent or better impact resistance for most clinical purposes. Its high tensile strength also makes it the preferred material for drill-mount and rimless frames, where stress concentration around drill holes would fracture polycarbonate.

The primary limitation is index of refraction: at 1.532, Trivex produces slightly thicker lenses than polycarbonate (1.586) for the same prescription. For most prescriptions below ±4.00 D, the thickness difference is cosmetically insignificant. For higher powers, it becomes relevant and mid-index materials are a better fit.

When to recommend Trivex: Children and active adults who need impact resistance with better optics than polycarbonate; patients with rimless or drill-mount frames; patients with moderate Rx (up to ±6.00 D) where weight is a priority; anyone with an Rx in the ±2.00 to ±4.00 D range who wants the cleanest peripheral optics possible in a safety-rated material.

When to avoid Trivex: High prescriptions above ±6.00 D, where the lower index produces unacceptable lens bulk. Trivex is also less available in specialty designs than polycarbonate, and commands a price premium that some patients are unwilling to pay.

For a detailed head-to-head on Trivex vs polycarbonate for rimless applications, see the discussion of prescription lens types in the context of frame material compatibility.

Polycarbonate: Ubiquity, Kids, Safety, and the Abbe Trade-Off

Polycarbonate has a refractive index of 1.586, a specific gravity of 1.20 g/cm³, and an Abbe value of 30. That last number is the defining clinical consideration. According to research published in 20/20 Magazine, for a polycarbonate lens at powers of +4.00 D and above, “lateral color errors [are] more than twice that of the 0.12 threshold” for observable chromatic aberration. Below 2.00 D, however, “lateral color will not be noticeable to the wearer.”

This creates a clear dispensing rule: polycarbonate is appropriate for patients at low-to-moderate powers who require impact resistance, and problematic for higher-Rx patients who will use their peripheral vision critically.

The material’s impact resistance is its defining advantage. Polycarbonate meets ANSI Z87.1-2020 high-velocity testing and is the industry default for children’s eyewear, safety glasses, and sport frames. Its UV absorption is intrinsic, requiring no additional UV coating.

When to recommend polycarbonate: Children under 16 (impact safety is the primary concern, Abbe value is secondary), sports and safety applications, patients with low-to-moderate Rx (under ±3.00 D) who need the cost-effectiveness of a widely available impact-resistant material, patients requiring ANSI Z87.1 certification.

When to avoid polycarbonate: High prescriptions (above ±4.00 D) for patients who notice or complain about chromatic aberration, patients with high cylinder (astigmatism) corrections who are particularly sensitive to lateral chromatic aberration, patients who prioritize optical clarity or color accuracy.

For patients with astigmatism at higher cylinder powers, the combination of off-axis viewing and polycarbonate’s low Abbe value tends to produce more complaints. Trivex or mid-index 1.60 are better choices in those cases.

Mid-Index (1.60, MR-8): The Optician’s Workhorse

The Mitsui MR-8 material at 1.60 index occupies a practical sweet spot. Its Abbe value of 41 is substantially better than polycarbonate’s 30, its specific gravity of 1.30 is only slightly higher than polycarbonate’s 1.20, and it produces lenses 15–20% thinner than CR-39 for the same prescription.

Mid-index 1.60 is the material where many experienced dispensers default for prescriptions between ±2.00 and ±6.00 D in patients who want thinner lenses but don’t need the full reduction of 1.67. It lacks ANSI Z87.1 certification, so it is not appropriate for occupational safety applications, but for dress eyewear it offers a well-balanced combination of optics, weight, and aesthetics.

When to recommend 1.60: Moderate-to-strong Rx (±2.00 to ±6.00 D) in patients who want perceptibly thinner lenses without the optical compromise of polycarbonate. Patients willing to pay a modest premium over polycarbonate but not justify the cost of 1.67.

High-Index (1.67, MR-7) and Ultra-High-Index (1.74, MR-174)

At 1.67, the MR-7 material has an Abbe value of 31, specific gravity of approximately 1.36 g/cm³, and produces lenses roughly 25% thinner than CR-39 at the same prescription. At 1.74, MR-174 pushes the index further, with an Abbe value of 32 and specific gravity of approximately 1.47 g/cm³.

Both materials require AR coating. High-index materials have higher surface reflectivity than lower-index materials; without AR treatment, 1.67 lenses reflect roughly 7–8% of incident light, creating ghost images and reducing contrast.

The Abbe values of 31–32 place these materials in polycarbonate territory for chromatic aberration. The performance difference from polycarbonate at high Rx is modest because at very high powers, the primary driver of perceived image quality is the magnitude of the aberration from the prescription itself, not from the material. For prescriptions above ±6.00 D, the cosmetic benefit of reduced lens thickness typically outweighs the Abbe trade-off.

When to recommend 1.67: Prescriptions in the ±4.00 to ±8.00 D range where thickness is a cosmetic concern and the patient understands the need for AR coating. Strong Rx patients who have adapted well to polycarbonate in the past (indicating they are not sensitive to low-Abbe materials) are good candidates.

When to recommend 1.74: Prescriptions above ±6.00 D, particularly for high-myopes who want the thinnest possible lenses in fashion frames. The cosmetic improvement over 1.67 is measurable for powers above ±8.00 D. Cost is a barrier: MR-174 lenses at this power are among the most expensive standard ophthalmic lenses available.

Estimating final lens thickness for specific Rx values and frame dimensions is practical to do before ordering. Lens thickness formulas and material indexes explain the underlying calculations. The minimum uncut lens size for a given frame also constrains which index is worth paying for in small frames.

Rx-Driven Material Recommendations

One pattern worth flagging from dispensing practice: the most common complaint with high-index 1.67 is not the cosmetics. It is the chromatic fringing on high-contrast edges (white text on black backgrounds, window frames against bright sky) that Abbe 31 makes unavoidable in peripheral gaze. Patients who already wear polycarbonate at powers above ±4.00 D and have never mentioned color fringing are solid candidates for 1.67. Patients who switched away from polycarbonate for optical reasons are not. Pre-warning before purchase prevents most post-fit complaints on high-index.

Frame geometry also matters. A large, round 54-mm frame in a strong minus prescription will show significantly more edge thickness than the same Rx in a small, rectangular 46-mm frame. Checking minimum uncut lens size against the frame’s boxing dimensions helps determine whether upgrading from 1.60 to 1.67 produces a visible cosmetic improvement or is purely an upsell. When fitting progressives, segment height constraints can also influence material choice if the fitting cross location pushes the optical center into a thicker zone.

Common Myths and Corrections

Myth: Polycarbonate and Trivex are essentially the same material.

They are not. Polycarbonate is a thermoplastic with index 1.586 and Abbe 30. Trivex is a urethane-based thermoset with index 1.532 and Abbe 43–44. Trivex is lighter (specific gravity 1.11 vs 1.20), has a 47% higher Abbe value, and handles tensile stress better around drill holes. Polycarbonate has a higher index (produces thinner lenses at equivalent power) and is substantially less expensive. These are meaningfully different materials with different optimal use cases.

Myth: High-index is always the right answer for strong prescriptions.

For prescriptions in a small-to-medium frame, upgrading from 1.60 to 1.67 produces a visible cosmetic improvement. For the same prescription in a small frame, it may not. The actual thickness reduction depends on the lens thickness formulas and material indexes and the specific frame dimensions. Additionally, high-index materials require AR coating and are more fragile than mid-index materials, so the upgrade carries trade-offs beyond cost.

Myth: Abbe value always matters.

For prescriptions below ±2.00 D, lateral chromatic aberration is below the perceptible threshold even with polycarbonate’s Abbe value of 30. According to the 20/20 Magazine analysis cited above, “lateral color will not be noticeable to the wearer” at powers below 2 diopters. Recommending CR-39 over polycarbonate to a -1.50 D patient on Abbe grounds is not clinically supported. Abbe value becomes meaningful above ±3.00 D, and clinically significant above ±4.00 D for the patient population most sensitive to chromatic aberration.

Myth: Polycarbonate does not need UV coating.

Correct. Polycarbonate absorbs UV intrinsically and does not require a UV coating. CR-39, however, provides minimal UV protection without a coating; it blocks UV at the 360 nm range but does not block the full UV-A spectrum to 400 nm. Trivex blocks UV to 400 nm intrinsically.

A Note on Coatings

All of the materials above benefit from anti-reflective (AR) coating, but for high-index materials it is not optional. The reflectivity of a lens surface increases with index of refraction; 1.67 and 1.74 lenses without AR produce visible ghost images that reduce the cosmetic and optical benefit of the premium material. Scratch-resistant hard coating is standard for all plastic lenses.

Coatings add complexity to material selection but are a separate topic with their own dispensing criteria. Hydrophobic and oleophobic top coats, blue-light filtering, and photochromic treatments all layer on top of the material properties discussed here.

Frequently Asked Questions

Saulo Garcia

I am a seasoned software engineer with over two decades of experience and a deep-rooted background in the optical industry, thanks to a family business. Driven by a passion for developing impactful software solutions, I pride myself on being a dedicated problem solver who strives to transform challenges into opportunities for innovation.