Diagnosis of Glaucoma Characteristic optic nerve changes Characteristic visual field defects Exclusion of other causes Intraocular pressure (IOP) usually > 21 mm Hg (but not required for the diagnosis) Glaucoma should be suspected in a patient with any of the following: Abnormal optic nerve on ophthalmoscopy Elevated IOP Typical visual field defects Family history of glaucoma Such patients (and those with any risk factors) should be referred to an ophthalmologist for a comprehensive examination that includes a thorough history, family history, examination of the optic disks (preferably using a binocular examination technique), formal visual field examination, tonometry (measurement of IOP), measurement of central corneal thickness, optic nerve and / or retinal nerve fiber layer imaging (using optical coherence tomography), and gonioscopy (visualization of the anterior chamber angle with a special mirrored contact lens prism).