5 Early Signs of Glaucoma That Mimic Ordinary Vision Changes and Often Go Undetected

Halos Around Lights at NightYou notice a coloured ring around a streetlight or an oncoming headlight and assume your eyes are just tired. This is one of the earliest reported symptoms of angle-closure glaucoma. The halo forms because raised intraocular pressure distorts the cornea slightly, scattering light before it reaches the retina. A 2019 study published in the Indian Journal of Ophthalmology found that angle-closure glaucoma accounts for more than half of all glaucoma-related blindness in India, and a significant portion of those patients had reported night halos for months before seeking care. The halo from glaucoma tends to be rainbow-edged and consistent. The blur from a dirty lens clears when you blink. Glaucoma's halo does not.
Headaches That Sit Behind One EyeA dull ache behind or above one eye, recurring in the evening or after long screen sessions, gets filed under stress or screen fatigue. When intraocular pressure spikes, even temporarily, the surrounding tissues register it as pain. This is particularly common in acute angle-closure episodes, where pressure can climb sharply within hours. The headache is real. The cause is not what most people assume. If the pain clusters around one eye rather than spreading across the forehead, and if it returns at similar times of day, it warrants an eye pressure check, not another paracetamol.
Peripheral Vision That Quietly NarrowsThe optic nerve damage that defines glaucoma begins at the edges of the visual field. Central vision stays sharp for years, which is exactly why the disease goes unnoticed for so long. You stop seeing the cup on the edge of the table, or you miss a person stepping into your path from the side, and you put it down to distraction. A 2020 report from the All India Ophthalmological Society estimated that nearly 90 percent of glaucoma patients in India are undiagnosed, and peripheral field loss is the most common finding that should have prompted earlier screening. By the time central vision is affected, the optic nerve has already lost a significant portion of its fibres. That loss does not reverse.
Eye Redness Without Irritation or DischargeMost people associate red eyes with infection, dust, or a poor night's sleep. But persistent low-grade redness in one eye, without the itching, discharge, or sensitivity to light that marks conjunctivitis, can indicate elevated pressure straining the eye's drainage system. This sign appears most often in secondary glaucoma, where an underlying condition like uveitis or prolonged steroid use has disrupted the trabecular meshwork that regulates fluid outflow. Steroid-induced glaucoma is an underreported problem in India, where topical corticosteroid eye drops are sometimes used without a prescription for extended periods. Redness that persists past a week without an obvious cause is a reason to measure pressure, not just switch eye drops.