Glaucoma is a disease where a person slowly loses their peripheral due to an increased pressure within the eye that damages the optic nerve.
In the early days of glaucoma detection doctwere mainly concerned about the level of intra-ocular pressure (pressure within the eye). If it was high you had glaucoma-simple as that. We also looked at the appearance of the nerve and tested the level of their peripheral vision by having them stare at a large blank area of black cloth and brought in a white marker on a stick to see when they first noticed it.
Those days are all but forgotten now. Today’s diagnoses of glaucoma require sophisticated equipment since our understanding of the disease has evolved.