Overview
Acute glaucoma, also known as acute angle-closure glaucoma or closed-angle glaucoma, is a sudden and severe eye condition that occurs when the drainage angle between the iris and cornea becomes completely blocked. This blockage prevents the aqueous humor (fluid inside the eye) from draining properly, causing a rapid and dangerous increase in intraocular pressure (IOP). Unlike chronic glaucoma which develops slowly over years, acute glaucoma strikes suddenly and requires immediate medical intervention to prevent permanent vision loss.
The condition occurs when the iris is pushed or pulled forward, closing off the drainage angle. This can happen when the pupil dilates in dim light or from certain medications, causing the already narrow angle to close completely. The resulting pressure buildup can damage the optic nerve within hours, making acute glaucoma one of the few true ophthalmic emergencies. While it accounts for only about 10% of all glaucoma cases, its sudden onset and potential for rapid, irreversible vision loss make it particularly dangerous.
Acute glaucoma typically affects one eye at a time, though individuals who experience it in one eye have about a 40-80% chance of developing it in the other eye within 5-10 years without preventive treatment. The condition is more common in certain populations, including people of Asian and Inuit descent, women, and individuals over 60 years of age. Understanding the warning signs and risk factors is crucial, as timely treatment can mean the difference between preserving vision and permanent blindness.
Symptoms
Acute glaucoma presents with sudden, severe symptoms that distinguish it from other eye conditions. The rapid onset and intensity of symptoms often bring patients to emergency care, which is fortunate given the urgent nature of treatment needed. Recognizing these symptoms quickly is vital for preserving vision.
Vision Changes
Diminished vision occurs rapidly as pressure builds, often progressing to severe vision loss within hours. Patients may also experience double vision and spots or clouds in vision, particularly halos around lights.
Eye Pain and Discomfort
Severe pain in eye is a hallmark symptom, often described as intense and throbbing. Many patients also report a foreign body sensation in eye, feeling as if something is stuck or pressing on the eye.
Eye Appearance
The affected eye typically shows marked eye redness due to congestion of blood vessels. The cornea may appear hazy or cloudy, and the pupil is often mid-dilated and fixed, not responding normally to light.
Severe Complications
Without immediate treatment, acute glaucoma can rapidly progress to blindness. General symptoms of eye distress become increasingly severe as pressure continues to build.
Systemic Symptoms
The severity of acute glaucoma often causes symptoms beyond the eye itself. Patients frequently experience severe headache on the affected side, often mistaken for migraine. Nausea and vomiting are common due to the vagal response to severe eye pain, sometimes leading to misdiagnosis as gastrointestinal illness. Abdominal pain may accompany these symptoms. Some patients report feeling generally unwell with weakness and malaise. The combination of eye and systemic symptoms can be so severe that patients may initially seek care for what they believe is a neurological or digestive problem rather than an eye condition.
Prodromal Symptoms
Some patients experience warning signs before a full acute attack. These prodromal symptoms may include intermittent blurred vision, especially in dim lighting, mild eye pain or ache that comes and goes, seeing rainbow-colored halos around lights, particularly at night, and mild headaches on the side of the affected eye. These episodes often resolve spontaneously when moving to brighter light (which constricts the pupil), but they indicate a narrow angle at risk for closure. Recognizing these warning signs provides an opportunity for preventive treatment before a devastating acute attack occurs.
Causes
Acute glaucoma occurs when the drainage angle of the eye suddenly becomes blocked, preventing the normal outflow of aqueous humor. Understanding the anatomical and physiological factors that lead to this blockage is crucial for both prevention and treatment of this sight-threatening condition.
Anatomical Predisposition
The primary underlying cause is an anatomically narrow drainage angle, where the space between the iris and cornea is already limited. In these eyes, the iris is positioned more forward than normal, creating a narrow channel for fluid drainage. This anatomical variation isn't a problem under normal circumstances, but certain triggers can cause the angle to close completely. People with hyperopia (farsightedness) are at higher risk because their eyes tend to be shorter, creating more crowded anterior segments. Additionally, as the lens of the eye naturally thickens with age, it can push the iris forward, further narrowing the angle.
Pupillary Block Mechanism
The most common mechanism for acute angle closure is pupillary block. When the pupil dilates to a mid-position (about 4-5mm), the iris can create a valve-like effect against the lens, blocking the flow of aqueous humor from the posterior chamber to the anterior chamber. This causes pressure to build behind the iris, pushing it forward like a sail catching wind, and closing off the drainage angle. Once the angle closes, aqueous humor cannot drain through the trabecular meshwork, causing rapid pressure elevation. This creates a vicious cycle where increasing pressure causes more inflammation and swelling, further blocking drainage.
Common Triggers
Several factors can precipitate an acute attack in susceptible individuals. Dim lighting causes natural pupil dilation, which is why attacks often occur in theaters, restaurants, or during evening hours. Emotional stress or excitement can trigger pupil dilation through sympathetic nervous system activation. Certain medications are particularly dangerous, including antihistamines, decongestants, antidepressants, and medications with anticholinergic effects. Eye drops that dilate pupils for examination can trigger attacks in predisposed individuals. Even prone positioning, such as during yoga or reading while lying down, can shift the lens forward and precipitate angle closure. Rapid changes in blood sugar levels and dehydration can also alter eye anatomy enough to trigger an attack.
Risk Factors
Understanding risk factors for acute glaucoma is essential for identifying individuals who may benefit from preventive treatment. While anyone can potentially develop acute glaucoma, certain factors significantly increase the likelihood of an attack.
Demographic Risk Factors
Age is a significant factor, with risk increasing substantially after age 40 and peaking between 55-70 years. Women are 2-4 times more likely to develop acute glaucoma than men, possibly due to having shallower anterior chambers on average. Ethnicity plays a crucial role - people of Asian descent, particularly Chinese and Southeast Asian populations, have the highest risk, while Inuit populations also show elevated rates. African Americans, who have higher rates of open-angle glaucoma, actually have lower rates of angle-closure glaucoma. Family history increases risk by 3-4 fold, suggesting a genetic component to anatomical predisposition.
Anatomical Risk Factors
Several eye characteristics increase susceptibility to acute glaucoma. Hyperopia (farsightedness) is a major risk factor because hyperopic eyes tend to be shorter with more crowded anterior segments. A shallow anterior chamber depth (less than 2.5mm) indicates limited space for aqueous humor drainage. Short axial length of the eye (less than 23mm) correlates with angle-closure risk. Thick crystalline lens, whether from natural aging or cataract formation, can push the iris forward. Small corneal diameter may indicate overall smaller eye dimensions. Previous acute attack in one eye dramatically increases risk in the fellow eye, with up to 80% developing an attack within 5 years without prophylactic treatment.
Modifiable Risk Factors
Certain medications and behaviors can increase risk in susceptible individuals. Medications with pupil-dilating effects should be used cautiously, including over-the-counter cold medications, certain antidepressants, and anti-anxiety medications. Prolonged time in dim lighting, excessive caffeine intake, and severe emotional stress can trigger attacks. Dehydration and rapid fluid intake can alter eye pressure dynamics. Some systemic conditions like diabetes may increase risk through lens swelling during blood sugar fluctuations. While these factors alone don't cause acute glaucoma, they can trigger attacks in anatomically predisposed eyes. Understanding and managing these modifiable factors is crucial for high-risk individuals.
Diagnosis
Rapid and accurate diagnosis of acute glaucoma is critical for preserving vision. The combination of clinical symptoms, examination findings, and specialized tests allows eye care professionals to confirm the diagnosis and initiate urgent treatment.
Clinical Examination
The initial examination reveals characteristic findings that strongly suggest acute glaucoma. Visual acuity is typically severely reduced in the affected eye, often to counting fingers or light perception only. The eye appears red with ciliary injection (redness concentrated around the cornea). The cornea often has a hazy, ground-glass appearance due to edema from elevated pressure. The pupil is characteristically mid-dilated (4-6mm) and poorly reactive or fixed. Gentle palpation may reveal a rock-hard eye compared to the fellow eye, though this is less reliable than measurement. The examiner must be careful not to apply pressure that could further elevate IOP or rupture a compromised globe.
Intraocular Pressure Measurement
Tonometry is essential for confirming dangerously elevated IOP. In acute attacks, pressure typically ranges from 40-80 mmHg (normal is 10-21 mmHg). Goldmann applanation tonometry is the gold standard, though handheld devices like Tono-Pen or iCare may be used in emergency settings. Extremely high pressures may actually cause falsely low readings due to corneal edema. Serial measurements help monitor treatment response. The unaffected eye should also be measured as it may show borderline elevated pressure or help establish the patient's baseline. Pressure in the fellow eye above 21 mmHg suggests bilateral narrow angles at risk.
Specialized Testing
Gonioscopy, examination of the drainage angle using a special mirrored lens, is the definitive test for confirming angle closure. However, corneal edema during acute attacks may limit visualization. Once the acute attack is broken and the cornea clears, gonioscopy reveals a closed or extremely narrow angle. Anterior segment optical coherence tomography (AS-OCT) can image angle structures even through a hazy cornea. Ultrasound biomicroscopy provides detailed images of angle anatomy and can identify mechanisms like plateau iris. B-scan ultrasonography rules out other causes of acute pressure elevation like tumors or hemorrhage. Visual field testing and optic nerve evaluation are performed after the acute phase to assess damage.
Treatment Options
Treatment of acute glaucoma is a true medical emergency requiring immediate intervention to lower intraocular pressure and prevent permanent vision loss. The approach involves rapid medical therapy followed by definitive laser or surgical treatment to prevent future attacks.
Immediate Medical Management
The first priority is rapidly reducing IOP using multiple medications simultaneously. Topical medications include beta-blockers (timolol), alpha-agonists (brimonidine), and prostaglandin analogs (latanoprost) applied every 5-15 minutes initially. Pilocarpine, a miotic that pulls the iris away from the angle, is crucial but works poorly when pressure exceeds 40 mmHg due to iris ischemia. Topical steroids reduce inflammation. Systemic treatments include intravenous acetazolamide (500mg) or oral (500mg twice daily) to decrease aqueous production, and intravenous mannitol (1-2 g/kg) for osmotic dehydration of the vitreous. Oral glycerol or isosorbide can be used if IV access isn't available. Pain management and antiemetics address severe symptoms.
Definitive Treatment - Laser Peripheral Iridotomy
Once IOP is controlled and the cornea clears, laser peripheral iridotomy (LPI) is the definitive treatment. This procedure creates a small hole in the peripheral iris using YAG or argon laser, providing an alternative pathway for aqueous humor to reach the anterior chamber. This bypasses the pupillary block mechanism and prevents future attacks. The procedure takes only minutes and is performed in-office. Success rate exceeds 90% for preventing future acute attacks. Prophylactic LPI is recommended for the fellow eye given the high risk of bilateral involvement. Complications are rare but may include temporary IOP elevation, mild bleeding, or glare symptoms.
Surgical Options
When medical therapy and LPI fail to control pressure, or when cataracts contribute to angle crowding, surgical intervention is necessary. Cataract extraction alone can deepen the anterior chamber and open the angle in many cases, particularly in eyes with thick lenses. Trabeculectomy creates a new drainage pathway when the angle remains compromised despite LPI. Goniosynechialysis can mechanically break adhesions between iris and angle structures. In severe cases with extensive angle damage, tube shunt surgery or cycloablation may be required. Combined procedures addressing both cataract and glaucoma are increasingly common. The choice depends on angle anatomy, lens status, and degree of optic nerve damage.
Long-term Management
After the acute phase, ongoing monitoring is essential. Regular IOP checks ensure adequate control, while gonioscopy monitors angle status. Visual field testing and optic nerve imaging assess for glaucomatous damage that may progress despite pressure control. Many patients require chronic glaucoma medications even after successful LPI. Fellow eye prophylaxis is crucial - without treatment, 40-80% develop acute attacks within 5 years. Patients must understand medication risks and warning symptoms. Genetic counseling may benefit those with strong family histories. Regular follow-up intervals depend on angle anatomy, pressure control, and optic nerve status but typically range from 1-6 months.
Prevention
Prevention of acute glaucoma attacks focuses on identifying high-risk individuals and providing prophylactic treatment before vision-threatening events occur. This proactive approach has dramatically reduced the incidence of acute attacks and their devastating consequences.
Screening and Risk Assessment
Regular eye examinations are crucial for identifying narrow angles before they close. High-risk populations, including people over 40, those with family history, hyperopes, and individuals of Asian descent, should undergo comprehensive eye exams including angle assessment. Simple screening tests like the penlight test (oblique flashlight test) can identify potentially narrow angles - a shallow shadow on the nasal iris suggests a narrow angle. More sophisticated screening uses anterior segment OCT or scanning peripheral anterior chamber depth analyzers. Van Herick technique during slit lamp examination estimates angle width. These screening methods help identify the estimated 10 million Americans with narrow angles who could benefit from preventive treatment.
Prophylactic Treatment
For individuals with anatomically narrow angles, prophylactic laser peripheral iridotomy prevents acute attacks with minimal risk. The procedure is performed on an outpatient basis when the eye is quiet and the cornea clear, allowing for optimal laser delivery. Studies show prophylactic LPI reduces acute attack risk by over 95%. The decision for prophylactic treatment considers angle anatomy, fellow eye history, access to emergency care, and patient lifestyle factors. Some practitioners recommend prophylactic treatment for all angles judged occludable on gonioscopy, while others reserve it for the highest-risk cases. Clear lens extraction is increasingly recognized as an alternative prevention strategy in eyes with significant lens-related crowding.
Lifestyle Modifications and Precautions
Individuals with narrow angles should be counseled about risk factors and warning signs. They should avoid medications with anticholinergic effects unless cleared by an eye care provider, including many over-the-counter cold and allergy medications. Caution is advised in dim lighting situations - using a small flashlight can help maintain pupil constriction. During dilated eye examinations, high-risk patients need careful monitoring. Patients should understand prodromal symptoms like halos around lights, intermittent blurring, or mild eye pain. Maintaining good general health, managing stress, and staying hydrated may help reduce attack risk. Emergency contact information and clear instructions about seeking immediate care for acute symptoms are essential components of prevention education.
When to See a Doctor
Recognizing when to seek medical care for potential acute glaucoma can save vision. The condition's rapid progression from onset to irreversible damage makes understanding warning signs and appropriate response crucial for anyone at risk.
Seek immediate emergency care if experiencing: Severe eye pain that doesn't improve with over-the-counter pain relievers, sudden vision loss or severe blurring in one eye, seeing rainbow halos or colored rings around lights, eye redness accompanied by pain and vision changes, nausea and vomiting along with eye symptoms, or a pupil that appears larger than the other and doesn't react to light. These symptoms, especially in combination, suggest acute glaucoma and require immediate evaluation at an emergency room or urgent care facility with ophthalmology coverage.
Schedule prompt ophthalmology consultation for: Intermittent episodes of blurred vision that improve in bright light, recurring mild eye pain or pressure sensation, occasional halos around lights at night, family history of glaucoma with any visual symptoms, or previous narrow angle diagnosis without prophylactic treatment. These may represent prodromal symptoms or intermittent angle closure that could progress to an acute attack. Evaluation within days to weeks can identify the need for preventive treatment.
Regular screening is recommended for: Individuals over 40 with risk factors like Asian ethnicity or hyperopia, anyone with family history of angle-closure glaucoma, patients taking medications that could precipitate attacks, and those with known narrow angles not yet treated. Annual or biannual comprehensive eye exams should include angle assessment. Don't wait for symptoms - anatomically narrow angles can be identified and treated before any attack occurs. The key message is that acute glaucoma is preventable in most cases with proper screening and prophylactic treatment, but once an acute attack begins, every hour of delay increases the risk of permanent vision loss.
Frequently Asked Questions
Can acute glaucoma affect both eyes at once?
While acute glaucoma typically affects one eye at a time, bilateral simultaneous attacks can occur in about 5-10% of cases. This is more likely with systemic triggers like certain medications or during bilateral dilated eye exams. However, if you've had an attack in one eye, your other eye is at very high risk (40-80%) of developing an attack within the next 5 years without preventive treatment. This is why prophylactic laser iridotomy is recommended for the fellow eye.
How quickly can vision be lost during an acute glaucoma attack?
Vision loss can occur remarkably quickly during an acute attack. Permanent damage to the optic nerve can begin within 6-12 hours of pressure elevation above 40-50 mmHg. Complete, irreversible blindness can occur within 24-48 hours without treatment. This rapid progression is why acute glaucoma is considered a true ophthalmic emergency requiring immediate treatment, unlike chronic glaucoma which causes damage over years.
Are there any warning signs before an acute attack?
Yes, many patients experience prodromal symptoms before a full acute attack. These include intermittent blurring of vision (especially in dim light), mild eye pain or headache, seeing rainbow-colored halos around lights, and mild nausea. These episodes often resolve when moving to brighter light or sleeping (which constricts the pupil). Recognizing these warning signs provides an opportunity for preventive treatment before a devastating acute attack.
Can acute glaucoma be cured permanently?
While the acute attack can be treated and future attacks prevented, any vision loss from optic nerve damage is permanent. Laser peripheral iridotomy successfully prevents future attacks in over 90% of cases by creating a permanent opening for fluid drainage. However, some patients may still need ongoing treatment for chronic glaucoma if the drainage system was damaged during the acute attack. The key is prevention and rapid treatment to minimize permanent damage.
What medications should I avoid if I have narrow angles?
If you have narrow angles, you should be cautious with medications that can dilate pupils, including many antihistamines (like diphenhydramine/Benadryl), decongestants (pseudoephedrine), tricyclic antidepressants, anti-anxiety medications, motion sickness patches, and some antipsychotics. Always inform healthcare providers about your narrow angles before taking new medications. However, if you've had successful laser iridotomy, most of these medications become safe to use.
References
- Friedman DS, et al. Angle closure and angle-closure glaucoma: what we are doing now and what we will be doing in the future. Clin Exp Ophthalmol. 2012;40(4):381-387.
- Prum BE Jr, et al. Primary Angle Closure Preferred Practice Pattern. American Academy of Ophthalmology. Ophthalmology. 2016;123(1):P1-P40.
- Tham YC, et al. Global prevalence of glaucoma and projections of glaucoma burden through 2040. Ophthalmology. 2014;121(11):2081-2090.
- He M, et al. Laser peripheral iridotomy for the prevention of angle closure: a single-centre, randomised controlled trial. Lancet. 2019;393(10181):1609-1618.
- Wright C, et al. Primary angle-closure glaucoma: an update. Acta Ophthalmol. 2016;94(3):217-225.