Eyewear, explained
The Designer Glasses Editorial Team 
Strong prescriptions bend light before it reaches the eye, and that bending changes the size of the image a viewer sees — not the eye itself. Minus lenses, for shortsightedness, shrink the eye behind them. Plus lenses, for longsightedness, magnify it. The stronger the prescription, the more pronounced the effect. What actually causes the minification … Read more
Base curve is the curvature of a lens’s front surface — how steeply it bows outward, measured on a standard scale rather than as a specific power. A flatter base curve sits closer to the face and looks more restrained; a steeper one wraps further around, which is why sports and wrap sunglasses look so … Read more
Pupillary distance, usually shortened to PD, is the measurement in millimetres between the centres of your two pupils. It’s taken so that whoever makes your lenses knows exactly where to position the optical centre of each one — the point where the lens does its clearest, most accurate work sits directly in front of your … Read more
What is lens decentration? Decentration is the distance between a lens’s optical centre — the single point where it corrects vision with no distortion — and the centre of the pupil when the glasses are worn. Every prescription lens is made with an optical centre in a fixed spot; decentration is how far that spot … Read more
No lens is perfectly colourless. Every “clear” lens is a stack of materials — the base plastic or glass, plus anti-reflective, scratch-resistant and oleophobic coatings — and each of those layers absorbs or reflects a tiny amount of light unevenly across the visible spectrum. What’s left over reads as a faint tint, usually green, blue … Read more
Blue-light filtering lenses absorb or reflect a portion of the high-energy visible light at the blue end of the spectrum, usually via a coating or a tint built into the lens material. What it does is measurable in a lab. What it does for eye strain, sleep or long-term eye health is, at best, weakly … Read more
An oleophobic coating is a thin, factory-applied layer on the front and back of a lens that repels oil, water and dust, so fingerprints and smudges wipe away instead of smearing into a haze. It doesn’t change what you see through the lens — only how easily it stays clean. For most people who touch … Read more
A scratch-resistant coating is a hard, thin layer bonded to the surface of the lens that resists fine abrasion — the kind caused by grit, keys, dust and cloth rubbing against plastic. It does not make the lens shatterproof, scratch-proof, or immune to a hard knock. It just raises the bar for what leaves a … Read more
Trivex is a lightweight, impact-resistant plastic lens material developed as an alternative to polycarbonate. Both resist shattering and both block UV, but Trivex is slightly less dense, has noticeably better optical clarity, and behaves differently when drilled or edged into a frame. Neither is “better” outright — they solve overlapping problems in different ways. What … Read more
Polycarbonate is a lightweight thermoplastic used for both lenses and frames because it resists shattering far better than glass or standard plastic. It is the right choice whenever impact resistance matters more than absolute optical purity — sport, children’s glasses, safety settings and rimless designs among them. What actually is polycarbonate? Polycarbonate is a clear … Read more
About what you read here. Everything on The Designer Glasses is general information and our own editorial opinion. We research carefully and we say when the evidence is unclear, but we can be wrong, things change, and no article can know your particular situation. Please do your own research and make your own judgement rather than treating anything here as the final word. This is not medical advice, not a diagnosis, and not a substitute for speaking to an optometrist, optician or eye doctor about your own eyes, vision and eyewear. We are writers and researchers, not clinicians. We do not recommend prescription treatments or give doses. If something is painful, getting worse, or worrying you, please talk to a professional — going early is not an overreaction.