Frames, lenses and how to choose eyewear that suits you
Lens distortion at the edges happens because a lens is curved and thickest away from its optical centre, and light bends differently the further it travels from that centre. Bigger lenses, stronger prescriptions, and lenses cut off-centre from their blank all make the effect more visible toward the rim. It shows up as a faint … Read more
A lenticular lens is a lens with two zones: a small, optically active circle or oval in the centre that does the actual correcting, and a thinner, much less powerful “carrier” area around it that exists purely to fill the frame and hold everything in place. It’s a design used for very strong prescriptions, where … Read more
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
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
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
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.