A close family friend has a leopard gecko he purchased 8 years ago who appears to be having trouble seeing. He has always been a good eater but now he doesn't seem to see his food even when it's right in front of him. This is making it difficult for him to eat and he has begun to lose weight. There are no visible signs of illness or eye infection. Is this a common problem and does anyone have any ideas on what can be done to encourage him to eat?