When looking at a night light with almost closed eyes, I notice that the light becomes a vertical line. When tilting my head 90 degrees, the line becomes horizontal. Can this be explained by Heisenberg's Uncertainty principle? This question has been asked in another thread : "Squinting at light bulbs, what are those lines?", but it is closed for comments. The poster mentions interference patterns and the double slit experiment. I have seen videos where a laser is pointed at a narrow vertical slit and the pattern on the wall beyond is a horizontal line.