Acute glaucoma is caused by a sudden rise in pressure in the eye. It is often very painful, but is often easy to treat. This page describes the condition and the treatment. The are different types of acute glaucoma, but this page describes the commonest, acute angle closure glaucoma. Animation
The eye is partly filled with a watery fluid, called 'aqueous'. The aqueous is produced in the ciliary body, in the 'posterior chamber' of the eye.
Then the aqueous flows forward into the anterior chamber, and leaves the eye in a the eye's drainage system.
The eye's drainage system: aqueous (green arrow) drains from the posterior chamber, to the anterior chamber, through trabecular meshwork, through the canal of schlemm, and out through the episcleral veins into the blood stream. (This has nothing to do with tears; tears cover the front surface of the eye only.) enlarge
normal aqueous flow enlarge
The eye is partly filled with a watery fluid, called 'aqueous'. The aqueous is made in the middle chamber of the eye. The aqueous flows forward into the front chamber, and leaves the eye in a the eye's drainage system, through trabecular meshwork, canal of schlemm, and out through the episcleral veins.
From the drainage system, the aqueous flows into the blood stream.
Thus normally aqueous flows from the posterior to the anterior chamber, then out of the eye.
The first blockage occurs (red blob) when the iris contacts the lens; this pushes the iris forward to obstruct the flow to the trabecular meshwork (yellow blob) enlarge
First, the iris presses backwards on the lens of the eye. Every year the lens gets a little thicker, and so the gap gets narrower. Some drugs make the iris a little more rigid (Atrovent inhalers for asthma, some antidepressants). Animation
Oen day, perhaps when coming from a dark room to a light room, this blocks the flow of aqueous (red blob). This puts the pressure up little.
Next, the pressure pushes the iris further forward forward (pink square). Animation
And then this iris blocks the entrance to the trabecular meshwork drainage system (yellow blob).
Finally, as the aqueous cannot leave the the eye, the pressure in the goes up a lot, like a tyre being pumped up to much. This pressure is transmitted to the the optic nerve.
The eye ecomes reda and achy (see below). If the pressure is high enough for long enough the optic nerve becomes damaged (caved in or 'cupped') and the sight becomes damaged.
The condition may develop gradually ('chronic'), as with most glaucoma, and there are no symptoms. The condition may be identified by optometry tests or other eye examinations. (Chronic narrow angle glaucoma). Later, there may be headaches or loss of sight, but by then some vision is lost.
In some people mild attacks of acute glaucoma may be occurring. There may be episodes of blurred hazy sight and slight eye pain or headache.
But in some people the attack is severe, the eye becomes red, the pressure is very high, and there is sickness and vomiting and severe pain in the eye. Urgent treatment is carried out in the eye department.
This top photo is a healthy eye.
This bottom photo shows that the iris is pushed up, 'bowed forward', obstructing the trabecular meshwork.
This includes diamox (acetazolamide) tablets/injection, and eye drops. Resist cases may need more treatment, such as an injection into the eye to drain the aqueous. All this treatment lowers the pressure, to resolve the attack of glaucoma.
See animation Once attack of glaucoma is over, laser is needed to prevent the condition occurring again. PIs for professionals. Nearly always both eyes are treated to prevent an attack in the other eye.
An hour before laser
Drops are needed to make the pupil small. These may cause a headache. Tablets keep the eye pressure down for the first day, and these can make patients feel a little funny, with pins and needles.
'Laser' is a type of
very bright focused light.
The patients sit at the laser machine, then drops are used to anaesthetise the front of your eye, and a small contact lens is placed on the eye. When the button is pressed there may be a slight pain lasting a second or less.
The laser makes a tiny hole in the iris of your eye. The hole is invisible to the naked eye. Once the hole is made fluid can flow though to the front chamber and then out of the eye. This hole keeps the eye pressure down.
Week of laser
You need anti-inflammatory
drops for 2 weeks (such as dexamethasone), as well as your regular
glaucoma drops if you have any.
Occasionally the laser only goes half way through the iris, and you may need the hole completed a week or two later.
Month after laser
Many people do not need drops after 4 weeks, but some do.
Laser completely prevents an 'attack' of acute glaucoma, so this will never be a problem. Most people have the laser, are seen a month after, about 6 months later, and are later discharged to be followed up by their optometrist.
However, a few people with chronic angle closure glaucoma may still have a slightly high pressure even after laser, and they need drops indefinitely. Imagine an overflowing sink. If you remove the plug (with laser), there may still be a blocked trabecular meshwork, or entrance to the trabecular meshwork (peripheral anterior synechiae).
Technically the blockage is in the trabecular meshwork, which is the drainage system of the eye. The blue arrow is the site of the laser hole. If you need drops you will be followed up in the outpatient clinic. If your doctor thinks you are lucky enough not to need drops, always have your eyes checked by your optometrist every year as a precaution. See animation.
About one third of patients will not need drops after laser. One third will need drops. Of the other third, some may need drops later. Some of the patients needing drops may need treatment for plateau iris, which includes laser iridoplasty or cataract surgery (our page)
Aqueous flow in acute closed angle glaucoma, left. Right, aqueous flow is restored after cataract surgery. Enlarge
Thickening of the lens of the eye (cataract) contributes to the angle closure. This happens naturally as we get older, but may happen earlier if we develop a cataract. As cataracts are common as we get older, (and more common in smokers), we are more prone to acute glaucoma as we get older. Some patients with unusually small eyes may develop it at a younger age.
If you have a cataract then cataract surgery will also prevent attacks of angle closure glaucoma. As cataract surgery is becoming safer ophthalmologists are starting to recommend cataract surgery for patients with narrow angles .
A normal cataract is about 4.5mm thick, and the lens implant is about 1mm, so there is about 3.5mm extra room for the aqueous to circulate.
People with glaucoma generally have smaller eyes than normal (21mm long of less instead of the normal 22.4 mm). Taiwanese/Inuits/Chinese seem to have a different anterior chamber structure, and the lens may be further forward than usual. Taiwanese/Inuits/Chinese are much more prone to angle closure glaucoma than Caucasians.
normal size eye
smaller eye with narrower anterior chamber enlarge
See this page .
If you are a health professional and want to have a leaflet to give to give to patients, instead of this web page, see 120k Adobe PDF version. This Publisher is a Microsoft Publisher document 150k, and you are welcome to download it and print copies. You are welcome to make changes for your patients (you can edit the leaflet in Microsoft Publisher). You will need M Publisher 2000 to open and print the document. The document is The document can be printed out and photocopied to provide a double-sided leaflet 1/3 A4 size for your patients. The address is http://www.diabeticretinopathy.org.uk/leaflets/angleclosureglaucoma.pub