They experience misfirings of optical nerves, and make sense of it in their minds by picturing the entrance to the afterlife. (religion.blogs.cnn.com)
Sanctus also demonstrated Barbara's interest in the medical industry, which she developed in other films like Optical Nerves (her submission to the 1987 Whitney Biennial), and Vital Signs. (blog.creative-capital.org)
Or you can explain why this wave - length looks blue to us with details about our retinas and optical nerves and brain processes. (religion-online.org)