red eared slider, eye problem

[Stephaan]

My brothers red eared slider has been in the tank with its eyes closed all the time, its been like that for awhile. the other two sliders in the tank seem fine. Is this a sickness? it can open one of its eyes halfway through if it really tries though? please tell me what it is!

Thanks in advance

 

[coura]

http://www.austinsturtlepage.com/Care/medeyes.htm It would be good to take your turt to see a vet. What is the tank size, diet, temps, ligthing, etc?