While from the outside looking in, this symptom might appear to be a huge red flag to go see a doctor, for many patients, they might not even recognize or notice the symptom at all - let alone associate it with a brain tumor.
The main reason for this is because it is subtle, not sudden vision loss, which translates often to the patient not noticing a decline in their vision as it happens so gradually. It isn't until they begin to bump into things on the one side that they are experiencing the loss.
“This particular symptom or impaired peripheral vision is known as bitemporal hemianopsia,” says Christopher Carrubba, MD, co-director for Medical Education at Med School Tutors. “We often see this symptom with pituitary tumors that compress the optic chiasm, or part of the visual pathway.”