Blue blockers have become quite popular, but their effectiveness is a topic of debate. My colleague Samer Hattar, head of the chronobiology unit at the National Institute of Mental Health, and I agree that eliminating specific wavelengths of light, like what blue blockers do, is not a natural thing for our visual system and brain to experience.
Blue light is actually optimal for stimulating neurons in your eye, which set your circadian rhythms properly. So shielding yourself from blue light during the day or anytime you want to be awake could have detrimental consequences. If you do choose to wear blue blockers, the best time would be at night and in the evening when you're headed towards sleep.
However, I personally prefer to control my light viewing behavior by dimming the lights in the evening, which sets up the brain and body for sleep much better than simply wearing blue blockers. It's also important to note that if the light in your environment is bright enough, it doesn't matter if you're blocking out the blues. The cells in the eye will respond to other wavelengths of light.
So, while blue blockers aren't harmful, their benefits may be overstated, and there are other, potentially more effective strategies for managing light exposure and circadian rhythms.