December 4, 2024
Cat’s (And Dog’s) Eyes
The evenings are drawing in as we near the darkest day of the year. I’ve begun to notice that it is getting darker and darker as I drive home from work. The headlights of oncoming cars on the road are glaring more noticeably than they did even a few weeks ago. Yet even on the mundane commute home there are wonders to behold. I am referring in particular to “cats eyes”. Not the actual eyes of a cat, but those small glass beads in the middle of the white line, reflecting the lights of your vehicle to illuminate the centre of the carriageway.
Cat’s eyes, or reflecting road studs, are a world famous safety feature of road travel invented in the UK in the 1930’s. The idea was to find a way to guide traffic in the dark, rain or fog. The inventor, a Mr Percy Shaw of Halifax, was inspired to invent the reflective beads by the shine of a real cat’s eye. This shine is created by an anatomical quirk in the cat’s eye - the tapetum lucidum. This is a latin term meaning “bright tapestry”. The tapetum is a highly reflective layer of tissue behind the retina. Its purpose is to reflect light coming into the eye, enabling the animal to see in the dark.
Cats, dogs and horses, among other animals, have a tapetum lucidum. Humans, sadly, do not. Therefore these animals can see in the dark much better than we can. You are all familiar with the tapetum lucidum. If you snap a photograph of your pet in the dark, you will likely see two bright lights emanating from their eyes. It is this effect that Mr Percy Shaw sought to copy with his ingenious invention. The light generated by the “road” cat’s eyes contributed greatly to commuter safety. The invention came into its own during the London Blitz whenever a blackout was imposed, aiding clandestine travel at night. After World War II, cats' eyes spread across the world, and they are now used in a variety of colours in motorways in many countries.
So next time you see a cat’s eye in the road at night, you know that this simple invention has saved many lives. Percy Shaw had the genius to apply simple observation of natural phenomena to real-world situations to provide a practical solution. And, of course, we must also thank the cat!
