What an anti-reflective coating does
Every air-to-lens surface reflects a few percent of the light hitting it. On an uncoated lens that produces two effects: light bouncing off the front, which is what other people see as glare on your glasses, and light bouncing between the back surface and your eye, which reduces contrast in what you are looking at.
An anti-reflective coating is a stack of thin layers engineered so those reflections cancel. More light passes through, less bounces around. This is ordinary optical engineering — the same principle used on camera lenses — and the effect is directly observable rather than inferred.
In practice it is most noticeable under overhead office lighting, when driving at night, and on camera, where it stops your lenses appearing as two white discs.
What a blue light filter does
It attenuates part of the short-wavelength region, either by reflecting it with a coating or absorbing it with an embedded tint. The optical effect is real; whether it produces the claimed benefit is the part in dispute. The 2023 Cochrane review of 17 randomised trials found these lenses may not reduce eye-strain symptoms compared with ordinary lenses. How the filtering works optically is covered here.
| Anti-reflective coating | Blue light filter | |
|---|---|---|
| What it does | Cancels reflections at the lens surfaces | Attenuates part of the short-wavelength band |
| Can you verify it? | Yes — hold it under a lamp against an uncoated lens | Not without instruments, and few sellers publish data |
| Evidence for the benefit | Well-established optical principle; reduces glare and improves contrast | Eye-strain benefit not supported by pooled trial evidence |
| Typical add-on cost | Modest | Often more, despite the weaker case |
| Downside | Shows fingerprints; needs careful cleaning | Colour shift if strongly tinted; none if near-clear, because it does little |
| Worth adding? | Usually yes | Optional, and not worth a premium |
Why they get conflated
Partly because many blue-filtering lenses also carry an anti-reflective coating, so a buyer who notices an improvement has no way to attribute it. Partly because "anti-glare" is used loosely in marketing to mean either. And partly because the blue filter is the higher-margin upgrade, so there is little commercial incentive to separate them clearly.
When you order lenses, ask which one you are actually paying for. If the answer is not specific, that tells you something.