The nose and the eyes are connected. This is the so-called nose and tears. Your father's current condition has affected his vision. I suggest you ask the relevant doctor whether this is related to sinusitis. Go to the eye hospital and explain your father's condition to the ophthalmologist. Don't be afraid, and don't blindly trust what's on the Internet. Explain the situation to your doctor so they can prescribe appropriate medicine.
Hope it helps you