Glaucoma testing isn't just about taking the eye pressure and tonometers are still used and considered to be the most accurate way to check the pressure. Many people have an elevated eye pressure but do not have glaucoma. This is typically termed ocular hypertension and needs no treatment.
Glaucoma is diagnosed with ocular pressure testing, an OCT or HRT of the optic nerve to see if there is pitting damage due to the increased pressure in the eye, and visual field testing to check if any peripheral vision has been lost. Glaucoma damages the optic nerve. The pressure in the eye builds up and pushes the optic nerve back, causing a pit, or as we in ophthalmology call it, a cup. Cupping of the optic nerve is concerning when the cup to disc ratio (the size of the optic nerve compared to the amount of cupping) is over .5 or .6 depending on the doctor. If your doctor is concerned he will order more testing to determine if what he sees is glaucoma or ocular hypertension.