Eyewear, explained
The Designer Glasses Editorial Team 
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
What Is a High-Index Lens? A high-index lens is made from a material that bends light more efficiently than standard plastic, which means it can be made thinner and flatter for the same prescription strength. The trade-off is that this material handles colour less faithfully, so light can split slightly at the edges — a … Read more
An occupational or office lens is a prescription lens built specifically for the distances that matter at a desk — arm’s length to a monitor and closer for paperwork or a phone — rather than for driving distance or the far horizon. It trades away long-distance clarity to give a wider, more comfortable zone for … Read more
A bifocal has two distinct zones of correction — usually distance up top and near vision in a segment at the bottom, separated by a visible line. A progressive does the same job of covering multiple distances, but blends them into one lens with no line at all. The difference is as much about how … 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.