The amount of harm from an LED, like any other lamp, is determined by the built-in protection of the product, in combination with reasonable precautions taken by the viewer. Specific to LEDs, the wider the field of light (i.e. size of the illumination source) and the brighter (higher luminance) of that source, the more potential risk it carries for the retina. Proximity to the light source is also a consideration. One should not, for example, gaze up close into a light box of blue (or even white) LEDs for longer than 100 seconds (the maximum recommendation from the International Commission on Non-Ionizing Radiation Protection).
I found similar comments on other websites. Anyway, I'm not ready to buy a PW but to each their own, and PW is still much better than LCD.