Primary Open-Angle Glaucoma (POAG) generally has no symptoms in the early stages, which is why it is known as the “silent thief of sight”. Late stage glaucoma, if untreated, leads to loss of visual field. If this is in one eye only, it may go unnoticed until vision is profoundly affected.
An attack of Acute Angle Closure, a different type of the disease, will normally cause a red, painful eye with misty vision and haloes around bright lights. This normally occurs in small hyperopic (long-sighted) eyes. The pain can be bad enough to cause nausea and vomiting. Repeated closed angle attacks and/or a sustained raised IOP can lead to damage to the optic nerve, known as primary angle-closure glaucoma (PACG).