A friend of mine had one of his eyes operated on after a peice of metal got stuck in it. Now his iris glows like an animals when caught in headlights on occasion. Can anyone explain to me why it does this? I'm not sure if he had his iris replaced, or if that is even possible.
Glowing Iris?
I haven't heard of this before but I am sure that when they operated they would have to but something into the eye to make it stay in place and not move around. It is probably some of that still in the eye.
Reply:Animal irises do not glow from headlights.
The anatomy of the eye that glows is the tapetum, an image intensifying ocular element in front of the retina in nocturnal animals.
A human has no tapetum, but his retina will retro-reflect light naturally due to the Stiles-Crawford pointing effect of the photoreceptor waveguides. A large pupil facilitates the area reflected; hence it is most noticeable at night in flash photography.
Your friend may still have some metal in his eye that could augment reflected and scattered light. He could also have fluorescein or other dyes that "glow" (fluoresce) left over from the surgery in his eye.
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