As long as the doctor is an ophthalmologist with fellowship training in glaucoma, I would trust what they had to say. Unfortunately, many optometrists and even some ophthalmologists don't check carefully enough for less likely glaucomas that present with normal pressures in clinic. A glaucoma specialist should be able to perform gonioscopy to rule out intermittent angle closure glaucoma, pigment dispersion, pseudoexfoliation, normal tension glaucoma, and thin corneas leading to misreading of the pressures. If your current doctor is not a glaucoma specialist MD, get a third opinion from one. That being said, 4 years of stable exams is reassuring.
HV