Good Hope Eye Clinic

Chronic angle closure glaucoma

David Kinshuck

 

What is eye pressure?

normal aqueous flow

aqueous fluid flow, shown in blue (blue)

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.

From the drainage system, it flows into the blood stream. (This has nothing to do with tears; tears cover the front surface of the eye only.)

The diagram opposite shows how aqueous flows. The middle chamber is known as the 'posterior' chamber, and the front chamber the 'anterior' chamber. Aqueous flows from the posterior to the anterior chamber, then out of the eye


 

Anatomy   

the 'angle' of the eye...the drainage channel of the eye

Anatomy of the eye. Close up on right, fluid flow as below.

diagram of angle anatomyBlockage to aqueous flow

 

 

 

site of blockage and glaucoma

The eye is partly filled with a watery fluid, called 'aqueous'. The aqueous is made in the middle chamber of the eye, secreted by the ciliary body. The aqueous fluid normally flows forward into the front chamber, and leaves the eye in a the eye's drainage system (the trabecular meshwork and hen the canal of schlemm).
From the drain (canal of schlemm), the aqueous flows into the blood stream. (This has nothing to do with tears; tears cover the front surface of the eye only.) In open angle glaucoma the blockage is in the trabecular meshwork.
In narrow angle glaucoma the iris moves forward and blocks the 'angle'.

 

Why does the eye pressure go up?

If the drain of the eye blocks or is blocked, the fluid cannot drain out of the eye. If the fluid cannot drain out, the pressure in the eye goes up. This is like a tyre being pumped up and going a little 'hard'.
The extra pressure then presses on the nerve at the back of the eye.
The optic nerve is the 'electric wire' of the eye that takes messages about what you see to the brain. See animation.

 

normal aqueous flowaqueous fluid flow, shown in blue (blue) Here is the normal aqueous flow.
when the drainage channel is blocked, aqueous flow is directed to the back of the eye pressure rises

As aqueous fluid cannot drain out of the eye, flow is directed back and pressure rises

 

What is glaucoma?

a healthy optic nerve and a cupped damaged optic nerve

The pressure presses on the optic nerve at the back of the eye, and as the nerve is damaged the sight becomes reduced. As nerve becomes damaged, examination may show the damage as 'caved in'. Medically we call it 'cupped'.

What is chronic angle closure glaucoma?

If you have chronic angle closure glaucoma the front/anterior chamber is usually smaller than normally. (A simplified explanation!)

 

normal aqueous flow...deep anterior chamber

normal eye & fluid flow

aqueous flow in angle closure glaucoma

small eye...small eyes are more prone to narrow angle/acute glaucoma

Aqueous is 'made' in the ciliary body (blue blob), but cannot flow past the iris or out of the eye the normal way. Pressure is transmitted to the optic nerve which it damages.
The aqueous pushes the iris forward (see below) and animation .

Because the anterior chamber of the eye is smaller than usual, the process may begin with a blockage between iris and lens (opposite: norally there is a gap between the iris and less as above). As a result there is not enough space for the aqueous fluid to flow to the front chamber of the eye and out of the eye.
Then... the fluid pushes the iris even further forward, trapping more fluid in the eye (blocking the entrance to the drainage system). As the aqueous fluid cannot drain out of the eye, this puts the pressure up and damages the optic nerve. This is explained better in this animation.

 

Acute vs more gradual angle closure glaucoma

This blockage can develop all of a sudden, perhaps one day coming out of the dark into a well lit room, as the pupil reaches a 'mid-dilated' size. This causes 'acute glaucoma'.
The blockage may be more gradual, 'chronic narrow angle glaucoma'.

Alternatively, you may have open angle glaucoma (see) and then this extra blockage may develop...'open angle glaucoma with narrow angles'.  There are many different terms used to describe these conditions.

 

Ethnicity and acute glaucoma

Similarly some Asian patients (Taiwanese for example) or Inuits, are far more prone to acute of chronic narrow angle glaucoma at a younger age. In such communities screening services need to examine patients to identify patients who need laser iridotomies.

 

irido-lens contact is the start of the angle closure a partial blockage develops here (black) where the iris and lens are in contact
the irs gets pushed forwards by the aqueous 'iris bombe'

as the iris gets pushed forward, a secondary blockage develops here (black arrows) at the entry point to the trabecular meshwork and the canal of schlemm (the drainage system).

 

The iris...when it is pushed forward in this way blocks the entrance to the drain, so pressure goes up.

 

an ultrasound photo of the anterior chamber (Ophthalmology International)A photo with a normal anterior chamber above, and  narrow angles below (Ophthalmology International)

What do you notice?

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 episdoes of blurred hazy sight and slight eye pain or headache.

 

Laser treatment

The hole made with laser

Laser is the main treatment for this condition at the beginning. How to laser PIs for professionals

An hour before laser Before the laser you need drops to make your pupil small. These may give you a headache. Tablets keep the eye pressure down for the first day, and these can make you feel a little funny, with pins and needles.

 

iridotomy...the treatment of acute glaucoma hole made with laser allows fluid flow out of eye

The laser 'Laser' is a type of very bright focused light. You sit at the laser machine, then drops are used to anaesthetise the front of your eye, and a small contact lens is placed on your eye. When the button is pressed you may feel a slight pain lasting a second or less.

The laser hole 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.

Month after laser Many people do not need drops after 4 weeks. Occasionally the laser only goes half way through the iris, and you may need the hole completed a week or two later. See animation

 

After laser, you may need drops indefinitely

a close up diagram of the iridotomy

Laser completely prevents an 'attack' of acute glaucoma, so this will never be a problem. However, some 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 drain.The diagram opposite shows where the remaining blockage may remain (the black rectangle).

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)

 

narrow angle...normal aqueous flowaqueous flow in a younger patient

Cataract surgery in angle closure glaucoma

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 .   Reduced press if angles narrow JCRS 14

 

later anterior chamber narrows and aqueous obstructed

aqueous flow in a older patient (rarely patients can be younger...they will have small eyes)

cataract surgery is one of the treatments of angle closure glaucoma aqueous flow is restored after cataract surgery

 

 

Ethnicity and acute glaucoma

Similarly some Asian patients (Taiwanese for example) or Inuits, have narrower anterior chambers and crowded angles and are far more prone to acute glaucoma at a younger age. In such communities screening services need to examine patients, to pick out patients who need laser iridotomies.

 

For Professionals

See this page .

 

Leaflet download

a leaflet explaining angle closure glaucoma

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, 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. M Publisher is bundled as part of Microsoft Office. The only condition is that you let me know if there are any errors. The document is 150k. 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