Narrow-angle or closed-angle glaucoma – Acute glaucoma
Angle-closure glaucoma (also called narrow-angle glaucoma) is a specific type of glaucoma. It occurs when a patient's iris blocks the eye's pressure-regulating system called the trabecular meshwork or iridocorneal angle. When the drainage angle is partially blocked, eye pressure gradually begins to rise (chronic angle-closure glaucoma). If this happens suddenly, it is called acute angle-closure glaucoma. Glaucoma is a degeneration of the optic nerve caused by abnormalities in eye pressure. It is one of the leading causes of blindness in people over 60. Its most common form is open-angle glaucoma . Narrow-angle glaucoma is a rarer but often more aggressive variant.
What is angle-closure glaucoma?
Angle-closure glaucoma corresponds to an obstruction of the trabecular meshwork (the mesh that regulates intraocular pressure) by the iris (the colored part around the pupil).
The obstruction can be partial (chronic form) or total (acute form).
The obstruction leads to an overfilling of the aqueous humor. Intraocular pressure rises because the eyeball is not expandable.
It is this eye pressure that presses on the optic nerve at the back of the eye and causes its degeneration: this is angle-closure glaucoma.
Narrow-angle or closed-angle glaucoma
Angle-closure glaucoma can present in acute or chronic (slow) form:
Acute angle-closure glaucoma
Acute angle-closure glaucoma corresponds to a sudden increase in intraocular pressure.
The entire trabecular meshwork is obstructed and no drainage of aqueous humor is possible.
The blood pressure suddenly increases, going from a normal 15 mmHg to a peak of over 40 mmHg.
This is a genuine eye emergency!
Urgent consultation is necessary (< 24 hours) to avoid the risk of permanent sight loss.
Symptoms of acute angle-closure glaucoma
Symptoms of an acute glaucoma attack:
Vision suddenly blurred
Intense eye pain
Headache
Nausea and vomiting
Kaleidoscope vision – Seeing rings or halos in rainbow colors around lights.
Angle-closure glaucoma develops slowly in many people. This is referred to as the chronic form.
Patients are asymptomatic at first and are unaware of their condition until the lesions are severe or they experience an acute glaucoma attack.
One in three people (30%) suffering from chronic closed-angle glaucoma experiences a sudden blockage that causes an acute attack.
There are sometimes certain symptoms that should prompt investigation for mini-angle-closure attacks in cases of chronic glaucoma:
Kaleidoscope vision – Particularly when passing through darkness.
Morning headaches – Headaches affecting the eye socket.
Causes
There are many anatomical factors responsible for a narrow iridocorneal angle. These factors result in a "lack of space" in the eye and obstruction of the trabecular meshwork:
A forward-bulging iris (pupillary block) – This is the most common cause.
An excessively thick lens.
An iris that is thicker than normal.
An iris pushed upwards on the sides (plateau iris).
One or more of these factors can cause a progressive closure of the drainage angle, leading to an increase in intraocular pressure.
Risk factors
Some people are at a higher than normal risk of developing angle closure. These include:
Aged over 50.
Having family members with angle-closure glaucoma
Having an enlarged lens or a cataract.
Of Asian or Inuit origin.
Of the female sex.
Hyperopia – Eye too small.
Discuss your glaucoma risk with an ophthalmologist. People with more than one of these risk factors have an even higher risk of angle-closure glaucoma.
How is angle-closure glaucoma diagnosed?
The only reliable way to diagnose chronic angle-closure glaucoma is through a complete eye examination. Glaucoma screening that only checks intraocular pressure is insufficient to detect chronic angle-closure glaucoma.
During a glaucoma evaluation, your ophthalmologist will perform:
A measurement of your eye pressure
A gonioscopy – Inspection of the drainage angle of your eye
A non-dilated fundus examination – To examine your optic nerve and see if it is damaged.
An optic nerve OCT to count your optic fibers and of the drainage angle to superficially analyze your iris and trabecular meshwork.
If there is any doubt about the type of glaucoma (open or closed), the ophthalmologist may perform a UBM (high-resolution ultrasound). The examination involves analyzing your lens, iris, and drainage angle in the dark, with your pupil dilated. Ultrasound allows visualization behind the iris, unlike OCT of the angle.
How is closed-angle glaucoma treated?
Optic nerve damage caused by glaucoma is permanent; it cannot be cured.
Medications, lasers, and surgery can prevent the lesions from worsening.
Treatment of chronic angle-closure glaucoma almost always requires the use of laser or surgery to reopen the blocked drainage angle.
For most people, eye drops are also needed as an additional treatment to help control eye pressure.
Laser in consultation – Iridotomy and iridoplasty
There are two main types of laser surgery to treat chronic angle-closure glaucoma. Both reposition the iris away from the drainage angle, facilitating fluid drainage from the eye. These procedures are typically performed in the office under local anesthesia with eye drops.
Iridotomy – The laser creates a tiny hole in the iris. This hole facilitates the flow of fluid towards the drainage angle by bypassing the iris.
Iridoplasty – More discreet and less effective. The laser is used to retract the iris and move it away from the drainage angle. Its effectiveness is temporary and limited.
Operating room surgery – Cataract and trabeculectomy
Some glaucoma treatments are performed in the operating room. These procedures either reopen the obstructed drainage angle or create a new drainage channel to allow the aqueous humor to leave the eye.
Cataract surgery – Some patients have a thickened lens. This pushes the iris above the drainage angle, causing angle-closure glaucoma. If the lens is also cloudy, it is a cataract. Your ophthalmologist can remove the lens and replace it with a thin, clear implant, correcting vision. This reopens the drainage angle and helps reduce eye pressure.
Trabeculectomy – Your ophthalmologist creates a small flap in the sclera (white of the eye) and a small hole in the iris. They will also create a bubble (like a blister) with the conjunctiva (the thin membrane that lines the inside of your eyelids and covers the white part of your eye) called a filtering bleb. It is hidden under the upper eyelid and invisible to the naked eye. Fluid can drain from the eye through the hole in the iris, the flap, and into the bleb to lower intraocular pressure.
Diode laser – When the iris is pushed against the drainage angle by the ciliary body (organs that secrete aqueous humor), a laser treatment can be used to retract the ciliary body. This retraction repositions the iris and reduces aqueous humor secretion. Laser treatment is generally reserved for severe cases.
Medications – Eye Drops
Medications are generally used in conjunction with laser or certain surgeries because the trabecular meshwork has been damaged by several years of obstruction before the diagnosis was made.
The medications do not treat the angle-closure mechanism but provide a supplement to lower intraocular pressure.
What to do in case of narrow-angle or closed-angle glaucoma?
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Narrow-angle glaucoma is asymptomatic for a long time before degenerating into acute glaucoma.
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From the moment of diagnosis, it is important to assess the risk of progression to an acute flare-up.
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Iridotomy laser treatment is used preventively; it does not replace close ophthalmological monitoring.
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Eye drops do not treat the angle closure mechanism, therefore they are not used as a first line of treatment but simply as a complement to laser or surgery.
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Intraocular pressure is a misleading indicator in angle-closure glaucoma, as it can be normal during the day and double at night.
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Regular monitoring with intraocular pressure measurement, but especially an ophthalmological examination, OCT and visual field testing are necessary.