Gordaen’s Blog

Though the title sounds like it should be a metaphor, I actually want to write about reflective eyes. Have you ever wondered why the eyes of deer reflect oncoming headlights (we’ll save the stupidity of standing there until hit for another time)? The more you think about it, the more you realize that a lot of animals have reflective eyes, including cats, yet humans are left out.

If you wanted excessive detail about the structure of an eye, you’d probably visit Wikipedia (and you could even see a ridiculously high-resolution image of an eye). I promise to avoid making this article that long.

The retina is the part of your eye that actually responds to light. You’ve probably heard that it has rods (sensitive to light) and cones (sensitive to color). Nocturnal animals require and subsequently have more rods, whereas diurnal (i.e., active at day) animals don’t require as many rods. Despite all the rods that nocturnal animals have, the retina does not pick up all of the light that passes through it.

The tapetum lucidum (Latin for “bright carpet,” yeah, those scientists are clever…) is a reflective layer behind (though it can be within) the retina and is found in those animals that have reflective eyes. Essentially, the tapetum reflects light back to the retina for a second chance to pick it up. If humans had this special reflective layer, it would give us better night vision, but it would also decrease the clarity of our vision (since the reflected light interferes with the incoming light).

Interestingly enough, different cone cells respond to different wavelengths of light, giving us color vision. If we had an even greater variety of cones, we could pick up other wavelengths. Next to red, we would see infrared light and, next to violet, we would see ultraviolet. If we had a really wide variety, we could pick up radio stations, but the suicide rate would go up due to the DJ’s telling us how they never stop playing music but not understanding that we don’t want to hear their voices over the music…