This one started with a great question from a viewer, and honestly, we love a good “why.” Someone asked why we wouldn’t just lenticularize a high plus lens to make it thinner. It’s a fair question, and the answer says a lot about how lens design actually works, so we wanted to walk through it.
A Quick Demonstration
Here’s an easy way to picture the problem. Take a pair of glasses and turn them around backward. They’re still technically your prescription. The power is right. The PD is right. Nothing about the actual numbers has changed. But look through them and the world suddenly looks off. Why? Because the curve of the lens is now facing away from your eye instead of toward it.
That tells you something important: getting the prescription right on paper isn’t the whole story. The curve of the lens matters too.
Where This Comes Up With High Plus Lenses
This becomes especially relevant with strong hyperopic prescriptions, think plus eight, plus ten, plus twelve, or higher. With powers that high, it’s tempting to ask how thin the lens can be made. Chasing that thinness often means making compromises on curvature.
Say you’re working with a plus 13 and you want a high-index material like 1.74 or a polarized 1.67. The steepest front curve available in that design might only be an eight base. To hit plus 13 with that limited front curve, it can be tempting to lenticularize the back of the lens.
Why That Trade-Off Isn’t Always the Right One
Here’s the catch. When a lens is lenticularized that way, it starts to behave a lot like those backward glasses at certain angles of gaze. The eye is no longer looking through the lens perpendicularly, and that’s a problem.
Ideally, your eye should encounter a lens as close to perpendicular as possible. When it doesn’t, you get distortion. You get oblique astigmatism. You get unintended refractive error that wasn’t part of the original prescription. Put simply, looking through a lens at an oblique angle is not the same as looking through it straight on, even if the prescription printed on the lens hasn’t changed.
There are times this effect can be used intentionally to good effect, but as a general rule, it’s something lens designers work to avoid rather than lean into.
Why We Use Aspheric and Corrected Curve Designs
This is exactly why aspheric lenses and corrected curve designs exist. They’re built so that as your eye moves and looks through different parts of the lens, it’s still encountering that lens at an angle that keeps the optics accurate. The goal isn’t just a thin, cosmetically pleasing lens. It’s a lens that performs the way it’s supposed to at every angle of gaze.
So when we’re designing a high plus lens, thinness is only part of the equation. Curvature matters just as much, sometimes more, because the most attractive lens on the shelf isn’t always the one that gives the clearest, most accurate vision.