What is Acute Angle-Closure Glaucoma?
Glaucoma, a condition characterized by increased pressure inside the eye, can lead to damage to the optic nerve and vision loss if not treated early. There are two types – open-angle and closed-angle, and both can be primary or secondary, depending on if the front part of the eye is obstructed or not. This part of the eye, known as the anterior chamber, houses the space between the iris and the cornea, which can get blocked.
Primary glaucomas do not occur as a result of known eye diseases or other health conditions and typically affects both eyes. On the other hand, secondary glaucomas often affect just one eye and are associated with other eye or health conditions. Acute closed-angle glaucoma (ACAG) falls under the category of primary angle-closure glaucoma. An acute angle-closure (AAC) is an eye emergency that comes with an increased eye pressure, risking permanent damage and potential blindness if it doesn’t get treated quickly.
Acute angle-closure usually shows distressing and significant symptoms like severe pain around one eye, eye redness, quick vision loss, whole body symptoms, nausea, headache, seeing halos around lights, and vomiting. Non-eye doctors may mistake these symptoms for a brain condition, resulting in unnecessary brain scans and consultations with brain specialists before an eye exam is done.
AAC diagnosis is confirmed by a high pressure inside the eye, typically between 50 to 80 mm Hg, as measured using an instrument called a tonometer. An eye examination with a specialized microscope usually shows a shallow front part of the eye, eye swelling, a wide and rigid pupil, eye redness, and a closed angle. Treatment includes medications, laser therapy, and surgery to lower the eye pressure, ease acute symptoms, and prevent future angle-closures.
The normal pressure inside the eye ranges from 10 to 21 mm Hg. Changes in eye pressure can be influenced by the production rate of a fluid produced in the eye called the aqueous humor, the resistance to this fluid’s outflow through an area called the trabecular meshwork and Schlemm’s canal, and the pressure in the episcleral veins. In ACAG, the pressure inside the eye increases rapidly due to the blockage of the aqueous humor’s outflow. The key risk factor for ACAG is the structure of the front part of the eye, which can lead to a shallower angle.
What Causes Acute Angle-Closure Glaucoma?
Primary angle closure is a condition where the front part of the eye gets blocked either temporarily or permanently. This condition can either come on suddenly or develop over time. A sudden onset is called acute angle closure and happens when there’s a quick rise in eye pressure due to a stop in fluid flow. This stoppage is caused by a blockage in the iris that leads to a complete closure of the eye’s front angle.
The other versions of primary angle closure either happen intermittently or consistently over time. These forms are characterized by recurring episodes which are commonly undetectable but still cause high eye pressure and structural changes in the eye due to prolonged contact between the ‘trabecular meshwork’ (a part of the eye) and the outer edge of the iris. This contact and the resulting changes can lead to an impairment in the eye structure and function over time.
The obstruction of fluid flow in primary angle closure is usually because of different physical factors such as a shallow front part of the eye, lens size, forward positioning of the iris-lens diaphragm, and a narrow entrance to the front part of the eye. Excessive contact between the iris and lens stops the fluid flow from the back to the front of the eye, creating a pressure difference known as a ‘pupillary block’.
This ‘pupillary block’ can cause a change in the structure of the iris, leading to a further narrowing of the front area of the eye. This chain reaction continuously increases eye pressure, leading to the development of a clinical condition called ACAG.
The American Academy of Ophthalmology has guidelines that classify primary angle closure based on factors like the presence of a narrow angle, extensive contact between the iris and the trabecular meshwork, the presence of attachments between the iris and cornea, high eye pressure, and signs of damage to the optic nerve. There are classifications based on combinations of these factors: ‘primary angle closure suspect’ (an eye with the iris in extensive contact but no high pressure or attachments), ‘primary angle closure’ (a condition when there is extensive contact with either high eye pressure or attachments), and ‘primary angle-closure glaucoma’ (a condition involving nerve layer damage with or without damage to the optic nerve).
Risk Factors and Frequency for Acute Angle-Closure Glaucoma
In 2013, around 65 million people globally were affected by glaucoma. The number is believed to have risen to 76 million in 2020, and it may rise further to more than 110 million by 2040. Of these, one-third of cases are due to Primary Angle Closure Glaucoma (PACG), which is more likely to cause blindness than primary open-angle glaucoma.
Acute Angle-Closure (AAC) Glaucoma is deemed to be rare. It affects about 2 to 4 individuals per 100,000 in white populations. However, higher occurrences have been recorded in places like Singapore and Asia with 6 to 12 cases per 100,000 people.
- Age-related changes in the eyes increase the risk of Acute Angle-Closure Glaucoma (ACAG). It is most likely to develop between the ages of 55 and 65, with risk increasing over time.
- Women are 2 to 4 times more likely to have AAC than men.
- Certain ethnic groups, such as Southeast Asians, Chinese, and Inuits, have a higher risk of ACAG, while it is less common in black populations. Anatomical differences in the ciliary body and iris are thought to be the reason behind this ethnic variability. ACAG represents 6% of all glaucoma cases in white individuals.
- A family history and certain eye-related conditions increase the risk of developing ACAG.
- Over 60 medications are linked to AAC and are considered risk factors, especially for those with pre-existing eye conditions. Some of these medications include atropine, cyclopentolate, topiramate, sulfonamides, duloxetine, and phenothiazines. Regular eye check-ups are advised for those using these medications, particularly if they are at risk for AAC.
Signs and Symptoms of Acute Angle-Closure Glaucoma
Acute Angle Closure (AAC) usually comes on suddenly and severely. Symptoms could include eye pain or headaches, blurry vision or less clear sight, seeing rainbow-colored halos around lights, and feeling sick or vomitting.
When you go to the doctor, they might find:
- Your pupil in the middle of your eye is wide open and not changing size
- The blood vessels in the white part of your eye (conjunctiva) are swollen
- Your cornea, the outermost layer of your eye, is hazy or cloudy
- The white part of your eye appears very red
- The pressure inside your eye is much higher than normal, potentially reaching 60 to 80 mm Hg
- There’s slight haziness and small cells in the liquid inside your eye (anterior chamber), which shows inflammation
- A specific type of eye exam (gonioscopy) shows that the drain in your eye is completely closed
- The optic nerve, the part that sends visual information to your brain, appears swollen
Testing for Acute Angle-Closure Glaucoma
If you are suspected to have Acute Angle-Closure Glaucoma (AAC), several diagnostic procedures may be performed to make a correct diagnosis. These procedures include a slit-lamp examination, intraocular pressure measurement, visual field testing, and several more.
A slit-lamp examination allows your doctor to get a detailed view of the front part of your eye. This includes the cornea, iris, and the anterior chamber. Any abnormalities such as cornea swelling, redness in the white part of the eye, or an unusually narrow angle can be noticed during this examination.
Another critical procedure is the measurement of intraocular pressure (IOP), which is the pressure inside your eye. Increased IOP is a common sign of AAC and can be greatly increased during an acute phase. The pressure inside your eye is measured with a technique known as tonometry.
Imaging studies are usually not required for diagnosing AAC during an acute phase. The diagnosis can be made based on your symptoms, the results of the slit-lamp examination, and your IOP measurement.
If some drugs such as mannitol or glycerin are used as part of the treatment, a basic metabolic panel may be performed to check your kidney function and electrolyte levels. This is because these drugs can potentially affect your body’s electrolyte balance and kidney function.
A gonioscopic examination, done by an eye specialist, is crucial in diagnosing AAC. It checks the angle between the iris (colored part of the eye) and the cornea (the front surface of the eye) to evaluate the extent of closure. Your other eye might also be checked using gonioscopy, as it might reveal a narrow or almost closed angle due to the structure of your eyes which may make you more prone to AAC.
Glaucomflecken or grey-white spots on the front capsule of your lens could be visible during a slit-lamp examine. These spots could indicate past episodes of AAC.
Visual field testing with automated static perimetry and Optical Coherence Tomography (OCT) are key checks in managing AAC. Visual field testing checks how well you see light brought to different parts of your visual field. Repeated testing over time can provide important data about the progress of AAC and the effectiveness of the treatment.
OCT provides detailed images of the retina and the optic nerve head, which are important structures in the eye. It checks for damage caused by AAC by assessing the thickness of the retinal nerve fiber layer. It can also detect structural changes characteristic of glaucoma. OCT scans taken over time can monitor changes and assess how well the treatment is working.
In patients with AAC risk factors like hyperopia, shallow anterior chamber, or a history of AAC in the other eye, anterior segment OCT and ultrasound biomicroscopy can be useful. They provide detailed images of the anterior segment structures, which include the angle, iris, and ciliary body. They can help evaluate features associated with angle closure and assist in deciding preventive measures or future interventions.
Treatment Options for Acute Angle-Closure Glaucoma
The treatment for sudden and severe glaucoma, also known as acute angle-closure glaucoma, focuses on quickly reducing eye pressure. It does so by decreasing the volume of eye fluid (aqueous humor), blocking its production, and increasing its flow out of the eye.
The initial treatment usually involves a combination of medications to quickly lower eye pressure and relieve symptoms. Here are some of the commonly used medications:
Acetazolamide is given orally or intravenously (through the veins). It helps in reducing fluid production in the eye, thereby lowering eye pressure. It works by inhibiting a specific enzyme, which decreases the production of eye fluid.
If given intravenously, mannitol, a type of fluid that makes you urinate more, can decrease the volume of eye fluid and quickly lower eye pressure. It works by drawing fluid out of the eye.
Beta-blocker eye drops, such as timolol, are used to block the production of eye fluid. These drops work by blocking certain receptors in the eye, reducing eye fluid production.
Alpha 2-agonists, like apraclonidine, are used as eye drops to block the production of aqueous humor. They reduce eye fluid production and enhance its flow out of the eye.
Pilocarpine, a medication that makes the pupil smaller, is used as eye drops to increase the outflow of eye fluid. It does this by making the pupil smaller and increasing the tension of the colored part of the eye (iris), which helps open up the space between the iris and cornea, allowing the eye fluid to drain. Pilocarpine is usually administered once the eye pressure is below a certain level.
When a patient is experiencing an episode of sudden severe glaucoma, it’s important to closely monitor their eye pressure to make sure the treatments are effective. Frequent eye pressure measurements are needed to check the patient’s response to the treatment and to make any necessary adjustments. The frequency of these checks can vary depending on the situation, but it’s generally recommended to check eye pressure at least every hour until it stabilizes.
After the acute episode, the ongoing treatment is aimed at preventing future episodes and managing the underlying risk factors. Here are some commonly used treatments:
Laser peripheral iridotomy is often the treatment of choice. It involves using a laser to create a small hole in the colored part of the eye, allowing the eye fluid to flow from one part of the eye to another, bypassing the blocked areas.
A surgical iridectomy involves surgically creating a permanent opening in the iris to relieve the blockage. This treatment is typically reserved for cases where laser treatment doesn’t work or isn’t possible.
In some cases, lens extraction may be the first choice of treatment, especially when there are significant anatomical risk factors. It involves removing the eye’s natural lens, which can relieve the factors contributing to angle closure. This approach often helps in advanced cases of sudden severe glaucoma.
If high eye pressure persists after the sudden severe glaucoma episode, similar treatments to those used for open-angle glaucoma can be used. This includes eye drops, laser treatment, and surgical interventions.
Regular eye check-ups, vision field tests, and other tests to look at different layers of the retina (OCT) should be considered if the patient is at risk of developing high eye pressure and future damage due to glaucoma.
What else can Acute Angle-Closure Glaucoma be?
When someone is experiencing symptoms like high eye pressure, cloudiness of the eye’s surface (cornea), inflammation of the white part of the eye (conjunctiva) and the front part of the eye (anterior segment), there could be various conditions causing it. These are the same symptoms that people with a type of glaucoma known as Acute Angle Closure (AAC) have. Because of this, when a patient comes in with these complaints, doctors would consider several potential issues including:
- Allergic reaction in the eye (Allergic conjunctivitis)
- Eye infection caused by bacteria (Bacterial conjunctivitis, also known as “pink eye”)
- Eye infection caused by a virus (Viral conjunctivitis)
- An inflammation or infection of the cornea (Keratitis)
- Inflammation of the layers of the white part of the eye (Episcleritis or scleritis)
- An eye injury
- Damage to the eye caused by chemicals
- An ulcer on the cornea (Corneal ulcer)
- A type of glaucoma where the eye’s drainage canals are open but blocked (Open-angle glaucoma)
- Glaucoma caused by medication (Drug-induced glaucoma)
- A severe and rare form of glaucoma (Malignant glaucoma)
- Glaucoma caused by the growth of new blood vessels in the eye (Neovascular glaucoma)
- Glaucoma caused by a swollen lens in the eye (Phacomorphic glaucoma)
- An age-related eye condition where the eye’s natural lens becomes cloudy (Senile or age-related cataract)
- A condition where the lens inside the eye has moved from its normal position (Lens subluxation)
- A severe headache often accompanied by aura (Migraine headache)
- A type of severe recurring headache (Cluster headache)
- Bleeding between the white layer of the eye and the retina (Suprachoroidal hemorrhage)
Knowing these possibilities will help the doctor conduct appropriate tests to diagnose the correct condition.
What to expect with Acute Angle-Closure Glaucoma
The chances of patients recovering from Acute Angle Closure Glaucoma (AAC) significantly improve with early detection and quick treatment. A study that examined 116 cases of AAC noted that how soon the patients sought treatment and how long the acute episode lasted directly influenced their overall recovery. On the other hand, the study found that having high intraocular pressure (IOP) – the pressure inside the eyes – doesn’t greatly affect the long-term recovery of these patients.
Possible Complications When Diagnosed with Acute Angle-Closure Glaucoma
If Acute Closed-Angle Glaucoma (ACAG) isn’t caught and treated in its initial stages, it can lead to temporary vision loss or even blindness. The loss of sight usually starts from the edges of the visual field (peripheral vision) and then moves to the center (central vision). In some instances, ACAG can evolve into a more severe form of glaucoma called malignant glaucoma.
Malignant glaucoma is defined by a significant rise in the eye’s internal pressure, even when the small hole in the iris (patent iridotomy) is open. With this condition, the front part of the eye flattens due to an imbalance of fluid, resulting in an increase in internal eye pressure. This form of glaucoma, also known as aqueous misdirection syndrome or ciliary block glaucoma, is quite difficult to treat and progressively results in blindness.
Preventing Acute Angle-Closure Glaucoma
Patients who have experienced acute angle-closure glaucoma should be careful to stay away from low light conditions. This is because dim lighting can cause the pupils to widen, which can make the angle between the iris and cornea even narrower.
People with long sightedness, or hypermetropia, have a higher chance of getting angle-closure glaucoma. This is mostly because being long-sighted often leads to certain physical predispositions in the eye, which can lead to angle closure. These might include a shallow front part of the eye, or the lens of the eye being positioned more towards the front. A procedure known as LPI is recommended for preventing this in people who are at risk for AAC.
