These can be especially worrisome, but sometimes go undetected. Some patients experience a complete loss of vision, whilst some only present a partial loss. It depends on the size and the depth of the affected area and the damage might not be visible at first. The damage can change depending on the location of the tumor and its growth. Some of the changes in vision can be blurred vision, a sudden loss or a greying out of the visual field after abruptly standing up.