When shopping for eyeglass lenses, most people start with brands. Big-name lens makers often feel like a “safe bet” for quality, and optical shops lean into this—marketing brand names hard, usually with package deals to grab your attention.
But as shoppers get savvier, two trends are shifting how we choose lenses: We care more about what works for us personally and doing our research first. More of us are skipping the brand hype and digging into the actual specs that make a lens perform well. With so much info out there, here are the two non-negotiable specs you should prioritize:
Here’s a basic optical truth: When white light (which has multiple wavelengths, like all the colors of the rainbow) passes through a prism, it splits into those colors. That’s because different colored light waves bend (refract) by different amounts. Your eyeglass lenses act like tiny prisms—thanks to their curved front and back surfaces. That’s why you might see “rainbow edges” (called color fringing) around objects, especially near the edges of your lenses—where light hits at a steeper angle, making this split worse.
The Abbe number (also called the “dispersion coefficient”) is a measurement invented by German physicist Ernst Abbe to quantify how much a material splits light. The rule is simple:
- The higher a lens’s refractive index (how much it bends light to correct vision), the more it splits light—and the lower its Abbe number.
- The lower the refractive index, the less light splits—and the higher the Abbe number.
This matters for your lenses: If you pick a high-refractive-index lens to make your glasses thinner (great for strong prescriptions!), you’ll likely get a lower Abbe number—and more rainbow fringing.
After years of research, companies like Mitsui Chemicals found a middle ground: Their MR-8™ material balances high refractive index (for thinness) and high Abbe number (for clear vision), so you don’t get excessive color fringing. Below’s a quick reference for common lens materials, their refractive indices, and Abbe numbers:
A good lens needs to do three things reliably: help you see, see clearly, and see comfortably—for years. That depends on its physical strength: how well it resists breaking, cracking, or scratching. Here’s what to look for, broken down by two key traits:
Lenses take unexpected hits daily—think rimless glasses falling and the edges hitting the floor, or a kid knocking your glasses off a table. How well they hold up comes down to material toughness:
- Ceramic or glass lenses: They’re strong in some ways (they don’t bend easily) but brittle—they’ll shatter on hard impacts.
- Resin lenses: Toughness varies by material. Medium-refractive-index resin or acrylic lenses are less tough—they crack easily. But polyurethane-based materials (like Mitsui’s MR™ series) have great impact resistance: They bend instead of breaking when hit, so they rarely crack or chip.
Beyond drops, lenses deal with daily friction—wiping them with a cloth, rubbing against your shirt pocket, or picking up dust. If they aren’t scratch-resistant, they’ll get blurry fast.
Materials like Mitsui’s MR™ series bond tightly to their protective coatings, so the coating doesn’t peel off (a common issue with cheaper lenses). They also stand up to heat and friction better, so they avoid tiny cracks that weaken the lens over time.
Mitsui Chemicals’ MR™ line (including MR-8™, MR-10™, MR-174™, and MR-7™) is popular for a reason—it checks all the boxes for key specs:
- Balance of thinness and clarity: High refractive index (for thin lenses) plus high Abbe number (for no rainbow fringing).
- Lightweight: Lower density than many other materials, so your glasses don’t weigh down your nose.
- Durable: Tough against impacts, scratches, and heat—great for kids, athletes, or anyone hard on their glasses.
- Versatile: Easy for opticians to cut and fit into any frame style (rimless, semi-rimless, curved frames)—so you aren’t limited by your lens choice.
Next time you shop for lenses, don’t just ask “What brands do you have?” Instead, say:
- “What’s the Abbe number for this lens?” (Aim for 30+ if you want minimal color fringing.)
- “How tough is this material—will it hold up if I drop my glasses?”
Brands can be a starting point, but the Abbe number and toughness are what will actually make your lenses work well for you. Prioritize these specs, and you’ll end up with glasses that are thin, clear, and built to last.
