When something is identified as a placebo, that is not the same as saying it can't or won't help anyone. The placebo effect is a real, measurable phenomenon. As

When something is identified as a placebo, that is not the same as saying it can't or won't help anyone. The placebo effect is a real, measurable phenomenon. As a non-scientist I'm probably going to grossly oversimplify this, but when testing the efficacy of a drug or medical device the whole reason you need to have a control group taking a placebo (sugar pills, for example) is because the placebo will actually cause some people in that group to have a real, measurable improvement in whatever it is being measured. The only way to know if the real drug or device you're testing actually works is if the improvements experienced by the test group is better than the improvements experienced by the control group. Additionally, I think this research/review was focused only on whether blue light filters help reduce eyestrain in the general population. So saying it had no effect here doesn't necessarily rule out the possibility that they could help in individuals with specific medical conditions that weren't controlled for or factored in here, just that in the general case they seem to have no effect.