one eye closed

Question
QUESTION: Periodically, may hamster will have one of her eyes closed.  There is no discharge and she acts normal.  It lasts about a 1/2 hour then it opens again.  Would you have any clue as to what this is?
ANSWER: Hi Stacey,

    How old is your hamster? What type of bedding are you using?

---------- FOLLOW-UP ----------

QUESTION: She is approximately 2 years old.  We are using the pine bedding.

Answer
Hello again Stacey,

    First, you need to get rid of the pine bedding. This type of bedding and cedar bedding are toxic to hamsters and can cause many different health problems and in some cases, even death. It is best to use aspen bedding or a type like critter care.
    The eye problem could be caused from the pine bedding and old age. Older hamsters sometimes get this problem. If any "crusty" should develop over the eye, you can take a wet Q-tip and gently rub over the eye (from outside corner to nose) to help get it open. Do not try to pry the eye open with your fingers, as a hamsters eyelids are very delicate and can tear easily.
    If you have anymore questions, please write again.

Thank you for writing!