Hi, Thanks for writing in. Sorry to hear the progress of disease in your husband. In my experience with patients of GBM I and II have a higher survival than those with GBM III and IV. It is important to know the size, location and if there is any pressure effect due to the tumor. Most tumors cause brain pressure, swelling or edema due to slightly increased electrical activity in the surrounding brain. The bubble in his vision might be due to pressure on the optic pathway. This has to be carefully evaluated by doing a CT scan or MRI scan since the clinical exam is normal. This can be controlled by giving steroids and mannitol. The real problem is any change in appearance of the tumor and its pressure effect on adjacent structures. Cancer is a difficult condition to treat and every tumor behaves in a different way. However we must fight cancer till the end. Praying for a quick recovery for your husband