Narrow Angles and Primary Angle Closure Glaucoma
The spectrum of primary angle closure glaucoma begins with having a narrow angle. Patients with narrow angles but otherwise normal healthy eyes are called primary angle closure suspects. Before you can begin to understand angle closure glaucoma you need to understand what a narrow angle means.
Where is the angle? The diagram below is a helpful reference and will help you understand the anatomy. The angle is the location where the iris meets the sclera as shown in the diagram below. There are 4 important structures in the angle; iris, sclera, the trabecular meshwork, and the ciliary body. The diagram below shows that internal eye liquid called aqueous humor fluid is formed by the ciliary body and circulates between the lens and iris, passes through the pupil, and then drains into the trabecular meshwork.
The space between the iris and sclera varies in width between individuals. Nearsighted or myopic persons tend to have wide angle widths and farsighted or hyperopic persons tend to have narrower widths. When the space becomes so narrow that the iris makes contact up against the sclera the pathway to the trabecular meshwork is blocked and the angle is said to be closed. A narrow angle less than 10 degrees in width is at higher risk for closure.
Narrow angle- the iris is pushed up towards the trabecular meshwork narrowing the approach to the trabecular meshwork.
Closed angle-in this case the iris is pushed up completely into the angle and the trabecular meshwork is not visible.
What can happen if I have narrow angles?
A patient with a narrow angle who is susceptible to closure can develop a slow progressive form of closure where parts of the angle begin to close without causing any symptoms or a noticeable change in eye pressure (intraocular pressure or IOP). With time the extent of closure worsens and the IOP starts to increase and may become erratic. The high IOP causes damage to the optic nerve and results in irreversible vision loss. In others, closure can occur all at once leading to acute angle closure crisis. Acute angle closure is a very serious and the most dramatic form of angle closure where the angle completely closes all at once, and IOP suddenly rises to very high levels. The patient with acute angle closure complains of a rather sudden onset of blurred vision, rainbows around lights, headache, nausea, and vomiting. Such a crisis may be triggered by medications, illness, and even stress, but often no inciting event can be identified. The acute crisis can lead to irreversible damage to the optic nerve with permanent loss of vision. Emergency treatment is required to reverse the attack.
Who gets angle closure glaucoma?
Angle closure occurs in all races and ethnicities but is much more common in Asians and Eskimos. Farsighted or hyperopic individuals more commonly have narrow angles.
What is the treatment for narrow angles or angle closure glaucoma?
The definitive treatment is laser iridotomy by which a small hole is made in the iris to balance the pressure behind the iris and allow the angle to open. Most patients with narrow angles do well with just laser iridotomy. However, in some patients the degree of closure progresses to the point there is irreversible blockage of part or all of the trabecular meshwork necessitating use of glaucoma drops, additional forms of laser treatment, or even surgery in addition to laser iridotomy.
Laser iridotomy-the laser beam (green) penetrates the iris causing a small hole in the iris to be created.
After the iridotomy is made the iris becomes flatter and the angle opens allowing the internal eye liquid (aqueous humor) to drain into the trabecular meshwork.
How is laser iridotomy performed?
Laser iridotomy is an outpatient office procedure where laser energy is delivered to the iris creating a small hole which cannot usually be seen by the naked eye. After the laser treatment the patient will be given anti-inflammatory drops for about 1 week.
If I have a narrow angle is there anything I should avoid?
A patient whose angle is narrow enough to be at risk for closure should generally avoid medications such as decongestants and antihistamines for allergies, certain antidepressants and anti-anxiety medications, as well as medications for bladder and other urinary conditions, until laser iridotomy is performed. The patient should read the package insert on over the counter as well as prescription medications before use if they have been diagnosed with narrow angles and need laser. The patient should discuss what should be avoided with their physician who is prescribing such medications and whether it is safe to not use them until laser is performed. After successful laser iridotomy has been performed, use of such medications is usually permitted.
What should I expect after laser iridotomy?
Most patients have little to no symptoms after laser iridotomy. Mild discomfort during the first few days may occur and resolves relatively quickly with the use of anti-inflammatory drops for about 1 week. Rarely, chronic inflammation may occur, causing formation of adhesions between the iris and lens as well as in the angle necessitating the need for chronic anti-inflammatory medications such as steroid drops. Inflammation and use of long term steroid drops may accelerate the development of a cataract and increase in eye pressure. A cataract may also develop after laser iridotomy but is usually localized to the area of treatment. In addition, few patients may develop optical aberrations and complain of seeing a horizontal line after iridotomy. Although, the optical disturbances may occur, they often become less noticeable with time and seem to disappear altogether.
What happens if the laser iridotomy doesn’t open the angle?
Most patients with just narrow angles after iridotomy do well without the need for additional laser. A smaller fraction of patients may need additional laser treatment called iridoplasty. In some complex cases iridoplasty is still not enough and the patient may need cataract surgery to open the angle and lower eye pressure, or need glaucoma filtering surgery.