Glaucoma
A group of eye diseases that gradually damage the optic nerve, usually due to elevated eye pressure, leading to slow peripheral vision loss.
Try Glaucoma in the simulator →What it looks like
Early glaucoma is almost invisible to the patient — the earliest defects are small areas of dimness or missing vision in the mid-periphery (paracentral scotomas), nasal step defects (a step-like boundary on the inner side of vision), or arcuate scotomas curving from the blind spot. As damage progresses, these merge into a more obvious tunnel-vision pattern, where only the central area of sight remains clear. Many patients also see halos around lights at night and have impaired night vision.
Why it's often diagnosed late
Because the brain compensates by filling in across both eyes, people with early-to-moderate glaucoma usually don't notice their field defects until significant damage has occurred — sometimes when they fail a driver's vision test. This is why regular eye pressure checks matter, especially after 40 or with family history.
Also known as
Open-angle glaucoma · Tunnel vision