The short answer
Blue light lenses filter part of the blue end of the spectrum. Marketing says they prevent eye damage and fix screen strain. The evidence for the first is thin, and the second is better explained by how long you stare at a screen and how often you blink.
If they help you, they help as a comfort measure. They are not a health measure.
What blue light actually is
Blue light sits at the shorter, higher-energy end of the visible spectrum. The sun is by far your largest source of it; a screen is a small fraction of what you take in on a normal day outdoors.
What the evidence supports
- No good evidence that screen blue light damages the retina at everyday levels.
- Little evidence that filtering it prevents digital eye strain, which is mostly about sustained focus, reduced blinking and dry eyes.
- Some evidence for better sleep when screens are limited close to bedtime — but that is about timing, not about lenses.
- People who find screens uncomfortable often report less discomfort with a tint, which is worth something even where the mechanism is unclear.
Who might genuinely benefit
Shift workers, anyone on screens late into the evening, and people who find bright displays uncomfortable. If you are one of them, a light tint is a cheap experiment. If you are not, the money is better spent on an anti-reflective coating.
What to ask before you add them
- Which tint is this, and what does it add to the standard lens price?
- Will whites look yellow through it?
- If I don't like it, can the lenses be changed on this frame?
The rest of the screen problem
The things that reliably help screen discomfort cost nothing: look across the room every twenty minutes, keep the screen roughly an arm's length away, and set the room light so the display is not the brightest thing in it.