Buying Glasses: Prescriptions and Lenses

HEALTH · GLOBAL

Buying Glasses: Prescriptions and Lenses

Reading a prescription, lens index and coatings, varifocals and frames

Glasses are bought on the frame and determined by the lens, and the prescription contains everything you need to compare one quote with another.

Reading a prescription

Sphere is the main correction, minus for short sight and plus for long sight. Cylinder and axis describe astigmatism. Add is the extra power for reading in a varifocal or bifocal.

Pupillary distance is needed to make the lenses and is frequently omitted from a prescription. You are entitled to ask for it, and lenses made with a wrong measurement cause eye strain.

Lens index

Higher index materials are thinner for the same prescription. For a strong prescription, a high index lens makes a real difference to weight and appearance; for a mild one it adds cost for very little.

Aspheric designs are flatter and reduce the magnifying or minifying effect at the edges.

Coatings

Anti-reflective coating genuinely helps with night driving and screen glare and is worth having. Scratch resistance is standard on most lenses. Blue light filtering has weak evidence for eye strain or sleep.

Photochromic lenses darken outdoors and work poorly inside a car, since windscreens filter the ultraviolet that triggers them.

Varifocals

Take a few weeks to adapt and need accurate fitting, since the corridor of clear vision is narrow. A larger frame gives more room for the progression.

Cheap varifocals have a narrower usable area, which is what people notice.

Frames

The eye should sit near the centre of the lens, the frame should not press at the temples, and the bridge carries most of the weight.

Buying online

You need a current prescription and your pupillary distance, and a frame that suits your face and your prescription. Complex prescriptions and varifocals are better fitted in person.

Check the returns policy, since glazed lenses are frequently non-returnable.

Looking after glasses

Rinse before wiping, since dust dragged across a lens is what scratches coatings. Use a microfibre cloth and a proper spray rather than a shirt.

Store in a hard case, never rest them lens-down, and do not leave them on a dashboard, since heat warps frames and damages coatings.

Children

Children's eye tests are free in the UK and are worth doing before school, since undetected vision problems are frequently mistaken for learning or behaviour difficulties.

Sunglasses and prescriptions

Prescription lenses can be tinted and polarised, and a second pair as sunglasses is usually the most-used purchase a daily glasses wearer makes. Check the tint category, since the darkest are not legal for driving.

Ultraviolet protection is separate from how dark a lens is, so look for UV400 or a stated 100 percent.

Eye tests

Every two years at least, since a test checks for glaucoma and other conditions that cause no symptoms early.

WHERE TO BUY

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