www.diabeticretinopathy.org.uk

  

Glaucoma in diabetes

Links...sister site

This is a condition that may occur in people with and without diabetes. It is usually caused by too much fluid pressing on the nerve at the back of the eye, as explained below in more detail.

Parts of the eye

     
The eye is a round ball the size of a small tomato.
   
 
It is partly hidden behind the eyelids.
   
       
   
Imagine the eye turning as shown below...
       
       
       
     
turning more
..
       
       
then imagine 'cutting' through the eye ball...
   
 
.....this is the view used below to explain glaucoma.

The green arrow shows the flow of fluid, like water, through the eye
.

 

The optic nerve

The optic nerve is the 'electric wire' of the eye, taking messages about what you see on towards the brain. In the main type of glaucoma the optic nerve is pressed on by extra fluid in the eye, and this may damage the sight in the eye.

 

 

the optic nerve is the electric wire of the eye taking messages to the brain

How does glaucoma develop?

Everybody's eye produces a fluid like water in it's middle chamber, in the 'ciliary body'. This fluid then flows around the lens of the eye to the front chamber, as shown in the diagram below... the blue arrow.

Then, from the front chamber the fluid leaves the eye by entering a drainage meshwork, like the drainpipe of a sink or bath.

From this drainage system the fluid enters the bloodstream. see an animation (sister site)

In the common type of glaucoma this drainage system can block. The fluid gets trapped in the eye, and the pressure inside the eye goes up like a tyre being blown up to much.

This pressure or fluid then presses on the nerve at the back of the eye. If the pressure is high or continues for a long time, usually years, the nerve at the back of the eye may become damaged, and eventually the sight may be affected.

This pressure effect is shown by the red arrow in the diagram below.

 
The eye produces its own fluid, like a 'tap in the bathroom', in its middle chamber.

 

The fluid ...like water.. flows through from the middle to the front chamber, the eye.  The fluid then drains out of the eye through a 'drain', like the plughole of a sink. This flow is shown by the blue arrow.
If the drain blocks, the fluid cannot get out of the eye, and the pressure in the eye builds up like a car tyre being pumped up too much. (Shown by the red arrow.)
This pressure (red arrow) damages the optic nerve at the back of the eye, pressing it in.

 

 

Animated eye

 

Glaucoma animation

red = blood flow

green = aqueous flow

 

Your sight in glaucoma

At first the sight is normal,

A common type of loss of vision in glaucoma.

 

Severe glaucoma is not common if you have diabetes, but it can occur.

At first the sight is normal, but it if the glaucoma is severe, the sight may get  progressively worse as opposite.

You cannot 'feel' glaucoma, and usually would would not know there was anything wrong in the early stages.

The optometrist or ophthalmologist usually tests people with diabetes for glaucoma about once a year, as below.

 

 

then a small area of poor vision may develop.

 

This can extend, affecting much of of the sight,

 

or nearly all the sight.

 

How does the doctor or optometrist know you have glaucoma?

Glaucoma is found by an ophthalmologist or optometrist by

 

Treatment for glaucoma

The basic treatment for glaucoma in diabetes is eye drops, and the commonest is one of the beta-blocker drops such as betaxalol, teoptic (cartelol), or timolol. These drops switch the tap off that makes the fluid. You generally should not use these drops if you get asthma or breathing difficulties, and should use an alternative drop. They may slow the heart down (if they make you dizzy you should stop them) or make your ankles swell. Drops are discussed here.

 

Will you go blind?

Once the pressure reaches a satisfactory level the glaucoma should not get worse or get very slowly worse. A satisfactory pressure if the optic nerve is healthy is 18-20mmHg, but if the nerve is already damaged the pressure needs to be lower, and 10-12 would be ideal. (The pressure level needed also depends on your type of glaucoma. People with 'low tension glaucoma' need a lower pressure, for instance.)

 

More details

Above one treatment has been discussed. Other web-sites discuss details of other drops.

This explanation to the usual type of glaucoma that may occur in diabetes.
A more severe glaucoma is mentioned here (rubeotic glaucoma); this and other types of glaucoma are discussed in more detail on other sites, although the basic mechanism is similar to that above.

See

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