Quick answer: For a basic e-ink Kindle, there's little need, e-ink screens are reflective and emit almost no blue light. But backlit tablets (and e-readers with a bright front-light) used at night do emit blue light, and there blue light glasses help protect your sleep.
E-ink vs. backlit
- Basic e-ink (no front-light): reflective like paper, almost no blue light, glasses add little.
- Front-lit e-readers at night: use the warm light setting; glasses help if the light is bright.
- Tablets and phones: backlit and blue-rich, glasses genuinely help, especially in the evening.
For night reading
Whatever the device, reading in bed delays sleep if the screen is bright. Use a warm/night light setting, dim the room, and wear an amber lens to protect your wind-down, or read a front-lit e-ink reader on its warmest setting.
The bottom line: A plain e-ink Kindle barely emits blue light, so blue light glasses aren't really needed for it. For backlit tablets and bright front-lit readers at night, amber glasses (plus warm light and a dim room) protect your sleep.
