We found out why our Cleo got MBD today. We called the vet to be sure. The uvb light fixture had a plastic cover over the uvb light. We found while replacing the uvb light. My hubby was reading the zoo med tube uvb pkg. and it said no rays could get through plastic or glass. It also said if the screen was sm. you lose 50% of your light and uvb. The vet said yes that was true. So our next step is to call the company who makes the brand of light that is. I believe its All Living Things. I hope no other pet has to die a slow agonizing death like our sweet baby did!