Does Glaucoma Cause Headaches

Understanding Glaucoma and Headaches

Glaucoma is usually a painless disease. In fact, primary open-angle glaucoma – the most common type – is often called the “silent thief of sight” (www.brightfocus.org). Because eye pressure (intraocular pressure, or IOP) in open-angle glaucoma rises slowly over years, the eye’s pain sensors (in the trigeminal nerve) never get triggered. In practical terms, this means chronic glaucoma like open-angle glaucoma does not itself cause headaches (www.brightfocus.org). If someone with open-angle glaucoma does wake up with a headache, the cause is almost certainly something else – perhaps stress, migraine, sinus issues or more – and it should be evaluated on its own merits, rather than blamed on the glaucoma. Proper treatment for both the eye and the headache can be delayed by assuming a connection that isn’t really there.

That said, some forms of glaucoma do cause head pain. Below we contrast the painless “slow” glaucoma with the painful “fast” glaucomas and other scenarios where headaches really may be related to the eye. We will also discuss how to tell a serious glaucoma-related headache from an ordinary headache and what to do about it.

When Glaucoma Doesn’t Cause Headache: Primary Open-Angle Glaucoma

In primary open-angle glaucoma (POAG), the eye’s drainage angle stays open but the fluid drains slowly, so pressure creeps up over time. Because the rise in pressure is gradual, the eye has time to adapt and pain sensors are not activated. Doctors and vision patients alike often describe open-angle glaucoma as asymptomatic until the late stages of vision loss (www.brightfocus.org). In other words, most people with POAG will never feel an ache or headache from the disease itself.

It is crucial to appreciate this. If you have been diagnosed with POAG (or ocular hypertension) and you experience headaches, those headaches are almost certainly unrelated. They deserve a separate work-up – perhaps by your primary care doctor or a neurologist – and attributing them casually to “glaucoma” can be misleading. Likewise, if a patient has chronic headaches and also happens to have glaucoma, don’t assume one caused the other without evidence. Open-angle glaucoma should not prevent headache evaluation, nor should headache evaluation delay glaucoma care, but both deserve attention.

Key Point: Chronic, gradual IOP elevation in open-angle glaucoma does not trigger pain receptors. If an open-angle glaucoma patient has a headache, look for other causes (www.brightfocus.org).

Acute Angle-Closure Glaucoma: A Painful Emergency

By stark contrast, acute angle-closure glaucoma (AACG) is an emergency that usually causes severe, unmistakable pain. In angle-closure glaucoma, the front part of the eye suddenly becomes blocked: the iris bows forward and closes off the drainage angle. Aqueous fluid cannot escape, and intraocular pressure jumps dramatically – often well above 40–60 mmHg (normal pressure is ~12–22). This rapid pressure spike presses on pain-sensitive structures and leads to a throbbing, often blinding headache or eye pain.

The headache in AACG is typically severe and unilateral (on the side of the affected eye). It is often described as a deep ache around the eye, brow or temple (a frontal or periorbital headache). Patients might also see blurred vision, halos around lights, and feel nauseous or vomit as the IOP soars (pmc.ncbi.nlm.nih.gov). In clinics and textbooks, acute angle-closure attacks are classic for eye pain with headache/nausea. For example, German clinics note that acute angle closure often presents with headache and nausea, alongside a red eye and fixed mid-dilated pupil (pmc.ncbi.nlm.nih.gov).

The danger is that acute angle-closure is frequently misdiagnosed. A patient comes to the ER with a pounding headache, eye pain, and nausea, but if the red eye and pupil change are missed, it can be mistaken for migraine, cluster headache, sinusitis or even a stroke. Indeed, studies show many angle-closure patients end up in non-eye clinics first. In one series, almost one-third of acute angle-closure patients initially saw a non-ophthalmologist, and one-third of those had unnecessary brain imaging before the eye cause was recognized (pmc.ncbi.nlm.nih.gov). Other reports note 30–50% of angle-closure cases are first mislabelled as migraine or other headaches. Such confusion is dangerous: without urgent IOP-lowering treatment, the optic nerve can be irreversibly damaged within hours.

Key Points: Acute angle-closure glaucoma causes an intense, sudden headache/eye pain on one side, often with nausea and blurred vision. It is a true glaucoma-related headache (pmc.ncbi.nlm.nih.gov). But it must be recognized as an eye emergency. Always check a patient’s eye if a headache is unilateral with visual signs or eye pain.

Intermittent Angle Closure (“Subacute” Attacks)

Before a full-blown acute attack, many people with anatomically narrow angles have milder, intermittent closures of the drainage angle. This often happens in low light or when the pupil dilates (for example, watching a dark movie or taking certain medications). During these episodes, IOP can rise moderately, leading to a dull ache or pressure in the eyebrow or forehead region, occasional halos around lights, and mild blurred vision. When the pupil narrows again and the angle reopens, the pain and blurring go away on their own.

These subacute attacks can easily be mistaken for tension headaches or migraine aura. Patients often don’t realize the connection, attributing the “movie–headache” or evening brow-ache to stress. Over time, however, repeated subclinical attacks can scar the angle tissues, making a full acute closure more likely.

BrightFocus notes that people with narrow angles may have occasional closures in dark environments – causing headache and blurred vision that resolve when the angle reopens . Such history (headache onset in dim light, one-sided eye discomfort or halos) should raise suspicion for intermittent angle closure.

Key Point: If headaches or eye aches tend to occur in dark rooms or with dilated pupils, especially with transient vision changes or halos, intermittent angle closure should be considered . An ophthalmologist can confirm narrow angles with gonioscopy.

Secondary (Neovascular/Inflammatory) Glaucomas and Headache

Certain secondary glaucomas are more likely to cause discomfort or headache. For example, neovascular glaucoma – where abnormal blood vessels cover the drainage angle (commonly in advanced diabetic eye disease) – can push IOP very high and cause pain. Patients often have severe eye pain and headache once the angle closes off, alongside nausea and blurred vision (www.brightfocus.org).

Similarly, inflammatory (uveitic) glaucoma – glaucoma arising from chronic eye inflammation – can cause dull aches. In these cases, inflamed tissues and mildly elevated pressure can irritate the ophthalmic branch of the trigeminal nerve (which supplies the eye), resulting in a chronic headache or discomfort around the brow. Although less dramatic than acute angle closure, these headaches are real and come from the irritated eye.

Key Point: In uncommon glaucomas with massively raised IOP (like neovascular glaucoma) or with chronic eye inflammation (uveitic glaucoma), patients can experience headaches or eye pain. These cases tend to have obvious eye disease signs.

Glaucoma Medications and Headache

Sometimes the very medications used to treat glaucoma can cause headaches as side effects. Notably:

Pilocarpine (an older eye drop) works by constricting the pupil and tightening the ciliary muscle to open drainage. This can lead to ciliary spasm and frontal headaches. A classic study of pilocarpine side effects lists “accommodative spasm” and “frontal headaches” as common ocular adverse reactions (www.sciencedirect.com). Clinically, patients on pilocarpine often complain of brow ache or head pressure.
Oral carbonic anhydrase inhibitors like acetazolamide (Diamox) can also produce systemic side effects, including headache, fatigue, and tingling. Patients sometimes note a diffuse headache after starting Diamox, likely related to its diuretic and metabolic effects (though it lowers eye pressure well).
Some people report mild periorbital discomfort or headache with the newer prostaglandin analogs (latanoprost, bimatoprost, etc.). While these drops mainly cause eye redness and eyelash changes, the ocular surface or lid sensations may rarely translate into headache in sensitive individuals.

Key Point: Brow ache or headache after glaucoma drops or pills can be due to the medication. For example, pilocarpine is well known to cause frontal headaches (www.sciencedirect.com), and systemic drugs like acetazolamide may also cause headache as a side effect. Always review new symptoms after starting a glaucoma medication.

Normal-Tension Glaucoma, Migraine and Vascular Links

A fascinating and still-debated area is the link between normal-tension glaucoma (NTG) and migraine or other headache disorders. In NTG, optic nerve damage and vision loss occur at statistically “normal” IOP (below 21 mmHg). Why the nerve dies in NTG is not fully understood, but many researchers point to vascular factors – the blood flow to the optic nerve head might be compromised.

Epidemiologically, NTG patients often have a history of migraines or headache syndromes more often than those with high-pressure glaucoma. For example, one study found 28% of NTG patients had migraine versus only 10–12% in high-pressure glaucoma or healthy controls (pubmed.ncbi.nlm.nih.gov). Another older Japanese study similarly reported headache and migraine features were more common in low-tension glaucoma patients than in POAG or normal subjects (pmc.ncbi.nlm.nih.gov). In plain terms, people with NTG tend to get migraines and headaches at higher rates.

Why? One idea is vascular dysregulation. Migraine (especially with aura) is thought to involve transient narrowing (vasospasm) of cerebral or ocular blood vessels. NTG patients often show Flammer syndrome traits – things like cold hands/feet, low blood pressure, and migraine sensitivity – suggesting their blood vessels also constrict more readily (pmc.ncbi.nlm.nih.gov). Flammer syndrome is a concept that binds together low blood pressure, migraine, high pain sensitivity, and altered blood-vessel behavior. One study found NTG patients had more Flammer symptoms (cold extremities, lower BP, migraines, headaches) than controls (pmc.ncbi.nlm.nih.gov). The speculation is that the same vascular “over-reactivity” causing migraines may also reduce blood flow to the optic nerve, harming it even without elevated pressure.

On top of that, some headache treatments might secondarily affect glaucoma. For instance, beta-blockers (like propranolol) are used for migraine prevention; they also lower IOP when used as eye drops. By contrast, a large recent cohort study found systemic calcium channel blockers (often used in migraine or hypertension) were associated with slightly higher odds of glaucoma, even controlling for pressure (pmc.ncbi.nlm.nih.gov). The idea is complex: maybe some heart or migraine medicines alter ocular blood flow or pressure in subtle ways over time. To be clear, these links are not proven cause-and-effect, but they are intriguing. If anything, they hint that a person’s blood-pressure meds or migraine treatment might modestly influence glaucoma risk or progression through vascular or pressure effects (pmc.ncbi.nlm.nih.gov).

Key Point: NTG patients do show a higher migraine rate, suggesting a shared vascular issue. Flammer syndrome terms explain the overlap of cold sensitivity, low BP, and migraines with NTG (pmc.ncbi.nlm.nih.gov) (pubmed.ncbi.nlm.nih.gov). Some migraine drugs (beta-blockers, calcium blockers) may have secondary effects on eye pressure or blood flow, so clinicians are watching this area closely (pmc.ncbi.nlm.nih.gov).

Telling the Difference: Migraine vs. Glaucoma-Related Headache

Clinically, differentiating a true glaucoma headache from a typical migraine or nuisance headache can be tricky, because the symptoms sometimes overlap (both can cause one-sided pain, visual blurring, and nausea). However, there are key clues on history and exam:

Onset and context: Angle-closure headache often begins abruptly, usually in one eye/side, and is tied to triggers like dim lighting or medication. Migraine often has a more gradual buildup, throbbing quality, and may have a known aura or triggers (like certain foods or stress). Asking about lighting conditions (e.g. “does it happen in dark movie theaters?”) or recent use of dilation meds can point toward angle issues.
Eye examination: In suspected angle-closure, an eye exam can be revealing. The classic signs of an acute attack include a red eye, a cloudy (edematous) cornea, and a mid-dilated, fixed pupil (pmc.ncbi.nlm.nih.gov). In contrast, migraine eyes are typically white (except for mild photophobia-related redness) and pupils react normally to light. Critically, checking intraocular pressure is safe and simple, and in angle closure it will be very high. Ophthalmologists will do gonioscopy (looking at the drainage angle with a special lens): if the angle is wide open (Schaffer grade 3–4), angle closure is essentially ruled out (pmc.ncbi.nlm.nih.gov).
Laterality and consistency: Glaucoma headaches are usually strictly on the same side as the eye problem. If your glaucoma is worse in the right eye and your headaches are always on the right, that’s suspicious. Migraines can move around or switch sides.
Response to treatment: Standard migraine therapies (triptans, rest in dark room) won’t relieve an acute angle-closure headache. Only lowering eye pressure (with drops or laser) will. Conversely, an actual migraine attack usually responds to migraine therapy and does not require an eye pressure-lowering drop.
Measuring IOP in the ER: Emergency recommendations increasingly stress that any patient with severe headache plus any visual complaint should get a screening eye pressure. Unfortunately, many ER visits for headache skip the painless tonometry test. But it can be lifesaving for the vision: if the pressure is elevated, the patient can be sent to ophthalmology immediately.

Key Point: If a severe headache comes with blurred vision, eye redness, or vomiting, measure the eye pressure. A fixed pupil and high pressure mean angle closure (pmc.ncbi.nlm.nih.gov). If exam is normal, the headache is likely a standard migraine or tension headache. Careful history (lighting trigger, consistent side) and exam help tell them apart.

Headaches After Glaucoma Procedures

Even glaucoma treatment can cause headaches, usually temporarily:

Laser peripheral iridotomy (LPI): This laser procedure makes a tiny hole in the iris to prevent angle-closure. It may cause a short-lived ache or brow pain in the first day or two as the eye adjusts, but this usually fades quickly. Some patients report mild headache immediately after or the next day, which typically resolves in days.
Post-operative headaches: After major surgery like trabeculectomy or tube shunts, patients sometimes notice headaches or brow aches, especially in the first few weeks. This is often due to fluctuations in pressure or minor inflammation. For example, when IOP suddenly drops post-surgery, the eye can become soft (hypotony), which some describe as a “deflated” feeling with ache, because the eyeball structure is slightly changed. Another cause can be stress and light sensitivity. Most of these early post-op headaches ease with time as the eye heals.
Late post-op headaches: If weeks to months after surgery a glaucoma patient begins getting new headaches or eye pain, it can be a warning sign. Excessive pressure might have crept back up (surgical scar blocking outflow) or inflammation may have flared. One rare but very serious cause is suprachoroidal hemorrhage (bleeding in the eye), which presents with sudden severe pain and headache and needs emergency care. Any late-onset headache after glaucoma surgery that comes with vision changes should prompt an urgent check of eye pressure.

Key Point: Minor headaches or brow aches are common right after glaucoma treatments (lasers, surgeries) and usually go away in days to weeks. But any new or severe post-op headache should trigger a pressure check to make sure the surgery is working and there is no complication.

A Practical Headache Plan for Glaucoma Patients

For patients and doctors, it helps to have a simple decision guide:

Likely Unrelated: If your glaucoma is the “silent” open-angle type, and your headache is like your usual tension or migraine (perhaps accompanied by typical aura, photophobia, or occurs in a familiar pattern), it’s probably unrelated. Treat it with normal headache care (OTC pain relief, migraine medication, stress reduction, etc.) and follow up as usual. Keep track of it, but don’t assume it’s a pressure issue.
A Reason to Check Eyes: If a headache is severe, on one side, and especially if you have any eye symptoms (blurry vision, halos, red eye, tearing), it should prompt an urgent IOP check and eye exam. For example, a patient with glares or a sick stomach plus forehead pain in low light should consider this a yellow flag. Inform your ophthalmologist or go to an ER with eye care – it’s better to be safe.
Ophthalmic Emergency (Same-Day Care): If you awaken with sudden, excruciating one-sided headache/eye pain accompanied by nausea, vomiting, and vision loss, treat it as an emergency. Call your doctor or go to the ER. Tell them upfront: “I have glaucoma and a one-sided eye headache with blurry vision and nausea.” Insist they check your eye pressure. This could be acute angle closure, which needs drops or treatment within hours.

Communicating is Key: If you have both a neurologist/migraine specialist and an ophthalmologist, make sure they talk or that you pass information. Don’t let headaches fall through the cracks. For example, you can say to your neurologist, “I also have glaucoma – if something changes with my eye, I will let you know,” and vice versa. Both kinds of doctors should be aware of the other condition so neither assumes the headache is “just glaucoma” or “just migraine” without evaluation.

Headache Diary: Keeping a simple log can be a lifesaver. Note the date, time, and severity of each headache, where the pain is (which side of the head/eye), associated symptoms (see stars or lights? feel sick?), and any new glaucoma medicines or changes (like starting pilocarpine or a new blood pressure pill). Also note if you were in a dark room or took a decongestant before it began. This diary will help your doctors see any patterns: for instance, if headaches only come with darkness – that points to angles. Or if increasing calcium blocker use matches more attacks – that’s useful too. Over time, these notes might reveal that recurring mild headaches are actually warning signs of intermittent angle narrowing, allowing you to get laser treatment before a full crisis.

Conclusion

In summary, most glaucoma patients do not get headaches from their eye disease. Primary open-angle glaucoma is painless. When headaches occur, they usually have another cause. On the other hand, certain glaucoma scenarios do cause real head or eye pain – particularly acute angle-closure attacks and some secondary glaucomas – and these should never be overlooked. Medication side effects and surgery recovery can also bring headaches. New research blurs boundaries (normal-tension glaucoma and migraine may share some vascular roots), but the bottom line for patients is simple:

Treat your glaucoma with your eye doctor as planned.
If you get headaches, evaluate them carefully. Look for red flags (side and eye signs).
Don’t assume a headache is “just migraine” if it has eye features, and don’t assume it’s “just glaucoma” if it feels like your usual migraine.
Communicate details of your symptoms to both your ophthalmologist and your family doctor/neurologist. Ask them if an eye exam or pressure check might be needed.
A little extra vigilance – measuring IOP when a headache strikes, noting triggers in a diary, and sharing that information with your doctors – can prevent misdiagnosis. It may be the difference between catching an angry eye pressure spike early or suffering irreversible damage because warning signs were dismissed.

Stay informed, and work with your healthcare team. With the right approach, you can manage both your eye health and your head health safely.

Sources: Reputable eye-health and medical journals and references have been used throughout (for example, BrightFocus Ophthalmology resources (www.brightfocus.org), medical studies on glaucoma and headache (pmc.ncbi.nlm.nih.gov) (pubmed.ncbi.nlm.nih.gov), and ophthalmic reviews (pmc.ncbi.nlm.nih.gov) (www.sciencedirect.com)). These sources confirm that POAG is usually painless, while acute angle closure causes headache (www.brightfocus.org) (pmc.ncbi.nlm.nih.gov), and that NTG patients more often have migraine history (pubmed.ncbi.nlm.nih.gov).