The pupil is the black spot at the center of the eyes. And the pupil will dilate or get smaller when the changes in light levels. Usually, dilated pupils will happen in low or dim light. Apart from the light levels, there are other factors that would cause dilated eyes such as medication or drugs. Also, cough and cold medications, decongestants, amphetamines, cocaine,and marijuana can cause dilated pupils.
Dear friend, dilated pupil is a common phenomenon that every one of us may suffer in every day. If we want to see something clearly, our pupil will dilate. You can check your eyes to see how it happens in the mirror. But this will not do harm to our eyesight. As to glassy eyes, I think there are many reasons. I saw many older people with some disease will have glassy eyes. Maybe this was caused by aging or medicines. And if someone is too tired or suffering great depress at this moment, he or she may have glassy eyes too. I don't know how to relieve this. But I think you can consult you doctors after having an eye exam.