I am having the same problem with my turtles (2 young desert tortoises). I didn't have it till I changed the substrate to alfalpha pellets and timmmy hay mix. Could it be one of those? I also keep them in a plastic wading pool with basking light and heat lamp. I remove the poo and any pellets that have gotten wet. Once a month I dump out completely and wash it out with the hose and some simple green. I have a 19yr male old as well. Just before hibernating his eyes looked a bit moister than usual but I also read that stopping eating (like before hibernating) can cause that too but last year they didn't look that way before he went under but he had eaten closer to the hibernating time than this year. Please any advice would be great! Thanks, Kandi