Lenses, coatings and contact lenses, explained
Spectacle lenses
Single vision
One power across the whole lens, for either distance or reading. Most first prescriptions are single vision.
Progressive
Distance at the top, reading at the bottom and everything in between, with no visible line. They take a few days to get used to and need accurate fitting heights, so the shop will measure you or ask for your measurements.
Lens index
A higher index bends light more, so the lens can be thinner. For low powers, 1.56 is fine. For stronger prescriptions (around ±4.00 and above), 1.60 or 1.67 keeps the edges thinner and the glasses lighter.
Coatings
- Anti-reflective: reduces reflections and glare from lights at night. Worth having on almost any lens.
- Blue-light filter: reduces some of the blue light from screens. Many people find it more comfortable for long screen use; it does not replace regular breaks.
- Photochromic: darkens in sunlight and clears indoors. It darkens less behind a car windscreen.
Sunglasses
Look for UV400, which blocks UV light up to 400 nm. Polarized lenses also cut glare reflected off roads, water and snow, which helps when driving or trekking. Dark lenses without UV protection can be worse than none, because your pupils open wider behind them.
Contact lenses
- Daily: worn once, then thrown away. No cleaning, lowest infection risk.
- Two-weekly and monthly: cleaned and stored overnight in solution, replaced on schedule.
- Toric: for astigmatism. Must match the sphere, cylinder and axis on your prescription.
A contact lens prescription is different from a glasses prescription: it includes the base curve and diameter. Order exactly what is written on it. If you have never worn contact lenses, have a fitting with an optometrist first.
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