one of our dragons has been keeping one of his eyes shut. he does open it occassionally but seems he cant keep it open for that long like he has something in his eye. we have inspected the eye under magnifying glass but cant see anything unusual.we bathed the eye with warm salt water and a cotton bud, after which he did seem to open his eye for approx 20mins, this is the longest time in couple of days. any advice what it could be and what to do it would be greatly appreciated. thanks.