I know what he means. Sometimes, when it's dark, your eyes can be more perceptive of other wavelengths besides visible light. I have seen, several times, very dim silhouettes moving across my field of vision. Sometimes I could make out bodies, but usually its just very fuzzy. I am certain that their fuzziness is caused by my eyes being naturally nearsighted. My glasses don't change the fuzziness.

I have only seen such silhouettes at night when there is snow on the ground and plenty of contrast. Last night I saw three separate ones, one of them crossed the road in front of me coming home from work and I felt a slight jar and I "hit" it and also felt really warm afterwards. Pure evil for sure. Luckily, I sleep next to my Bible so there is nothing giving me nightmares.