As you probably noticed by now, this whole website is designed with high contrast in mind. This is mainly to accommodate most low vision and blind readers. Some eye conditions such as Retinitis Pigmentosa develop with light sensitivity, or Photophobia which makes traditional webpage containing black characters on white background challenging and sometime impossible to use.
High contrast white characters on black background can help fix that issue to a certain level.
Depending on your eye disability, white characters on black background might still be too harsh. This is where color filters can dramatically help.. All mobile devices and Windows / Mac computers have filters you can apply to your screen. Look into your accessibility setting. You can give white characters a blue, orange, red or green tint,
Experiment with different color filters and when you finally select the one that works best for you, give those eye unfriendly websites another look. You might be surprised of the result.