Chronic angle closure glaucoma David Kinshuck |
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What is eye pressure? |
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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.)
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aqueous
fluid flow, shown in blue (blue)
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Anatomy |
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Anotomy of the eye. Close up on right, fluid flow as below. |
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Blockage to aqueous flow |
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'. |
What is eye pressure? |
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Here is the normal aqueous flow. |
aqueous
fluid flow, shown in blue (blue)
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Why does the eye pressure go up? |
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If the drain of the eye blocks or is blocked, the fluid cannot drain out of the eye. The optic nerve is the 'electric wire' of the eye that takes messages about what you see to the brain. |
As
aqueous fluid cannot drain out of the eye, flow is directed back and
pressure rises
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What is glaucoma? |
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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'.
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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!) |
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normal eye & fluid flow
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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 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 |
a partial blockage develops here (black) where the iris and lens are in contact
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. |
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What do you notice? |
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Laser treatment |
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How to laser PIs for professionals Laser is the main treatment for this condition at the beginning. An
hour before laser The laser The laser hole Month after
laser |
![]() The
hole made with laser
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hole
made with laser allows fluid flow out of eye |
After laser, you may need drops indefinitely |
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Laser completely
prevents an 'attack' of acute glaucoma, so this will never be a problem. 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. 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) |
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Cataract surgery in angle closure glaucoma |
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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. Cataract surgery As cataract surgery is becoming safer ophthalmologists are starting to recommend cataract surgery for patients with narrow angles . Ethnicity and acute glaucoma |
aqueous flow in a younger patient |
aqueous flow in a older patient (rarely patients can be younger...they will have small eyes) |
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aqueous flow is free again after cataract surgery
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For Professionals |
See this page |
Leaflet download |
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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. |
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The address of this site ('org' changing to 'nhs') is changing from http://www.goodhope.org.uk/departments/eyedept/ to http://www.goodhope.nhs.uk/departments/eyedept/ |
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