I'm 20 male, no eye/health problems.. anyway, when I look at the blue sky (doesn't work on anything else even if it's bright?), When I close ONE eye and DE-FOCUS the open one, and just 'stare off' after about a few seconds it's like a slowly reddish/dark brown area appears - it looks like a after image, but as soon as I focus again it dissapears, and doesn't work with both eyes open? It's kind of like when it's dark and you keep staring, and things all go pitch-black until the slightest subtle eye movement brings everything back.