First, it is worth describing the generally accepted definitions of glaucoma, which is the primary cause of irreversible blindness in the developed world. It has been estimated that the number of glaucoma cases will reach 76 million in 2020, rising to 112 million in 2040. (1)
Most glaucoma is age-related, therefore, as populations age and we live longer, we would expect the prevalence to increase. There are many forms of glaucoma. However, the three groups of glaucoma we mostly encounter in practice, in patients who are taking ocular hypotensive drugs, are;
- Ocular hypertension, where it is judged the patient’s IOP is higher than an agreed safe limit but where there is no detectable glaucomatous damage. Here, medications may lower IOP to reduce the risk of it occurring in the future.
- Primary open angle glaucoma (POAG) or chronic open-angle glaucoma (COAG), where the IOP is higher than the agreed safe limit, and detectable glaucomatous damage is already present.
- Normal pressure/low tension glaucoma, where the IOP is under the agreed safe limit, but typical glaucomatous damage is occurring.