I have looked on Animalplanet.com, Google, and Ask.com to no avail. There is nothing on his eye loss anywhere. If you know please reply. Thanks, xxy_xyy

chen chen lost his eye by a tree branch caught his eye .

he was playing as a baby and the other one did that by mistake.
Poor Guy.

This is verbatim from Chen Chen's entry in our "Meet the Orangutans" section:

At Nyaru Menteng Rescue and Rehabilitation Center Chen Chen was like any other baby orangutan; playful, curious and always up for a wrestle. Tragically, during a playful scrap, Chen Chen pierced his left eye with a stick. His eye was so severely damaged veterinarians had no choice but to remove it completely. From then on Chen Chen became known as "The Pirate," both because of his looks and a new, very changeable, personality. Through the ordeal Chen Chen became good friends with a younger smaller male called Donald... Donald seemed to be the only one willing to put up with his mood swings.

I don't know if you have recieved an answer yet to your question about Chen Chen. I have just joined on and loged on for the first time (2/9/2008). Chen Chen lost his eye while swinging in the trees. He fell and a branch took his eye out. They mentioned it on an earlier episode. Every time I see him my heart goes out to him. He seems to addapted very well to his enviroment with yhe one eye.

if you get a chance to see Orangutan Diary you will see Chen Chen's eye being operated upon. It happened about 2 years ago.