There is no way to avoid the fact: DandyLion, our semi-feral cat, has scary eyes. I know what causes red eye in humans when they're exposed to flash photography: it's light that reflects off the fundus at the back of the eye, and back again through the pupil. The red color comes from the choroid, which is behind the retina, and quite how much red there is depends on the amount of melatonin in the layers behind the retina.
So far so good. But large luminous orangey-yellow glowing eyes? This will be light reflected back from her tapetum lucidum - her "bright tapestry" - a layer of membrane behind the retina - and the extraordinary strength of this reflection should mean that she's exceptionally good in seeing well in very low-lit conditions. Indeed, this is where the idea of "cats' eyes", as reflecting road markings, comes from (is this a US, as well as a UK term)? I've never, however, seen anything as bright as this - every time our little Lion has her picture taken by flash: it's truly spooky.