My dad is 79 with GBM resection and he keeps eyes shut all the time. He yells back at us if we remind him to keep them open while eating.

Kwood3414, he could be keeping his eyes shut because everything now seems way too bright for him. Or his eyes are very dry. That in itself can be very uncomfortable. No wonder he gets upset.

Has Dad tried wearing sunglasses in the house to see if that would help? If it does help, then set up an appointment with an eye doctor.