Glaucoma is usually caused by too much fluid pressing on the nerve at the back of the eye and can also be caused by having a reduced blood flow.
Glaucoma is not a single disease, but represents conditions that occur for different reasons with the final event being optic nerve damage and visual field loss.
Types of glaucoma
- Chronic open angle
- Narrow angle
- Angle dysgenesis
The optic nerve is the ‘electric wire’ of the eye, and it takes messages from the eye to 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.
How does glaucoma develop?
Everybody’s eye produces a fluid like water in its middle chamber. This fluid then flows around inside the eye to the front chamber, as shown in the diagram below.
Normally fluid is made in the ciliary body and circulates to the front chamber, where it drains through the trabecular meshwork out of the eye.
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. The trabecular meshwork is a type of filter system.
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.
The pressure reduces the blood flow in the tiny blood vessels in the optic nerve.
Intraocular pressure is strongly related to the metabolic syndrome. Metabolic syndrome and other insulin resistance-related features, including hepatic steatosis, increased left ventricular mass, and proteinuria, are strongly associated with IOP
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 (the trabecular meshwork).
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.This pressure damages the optic nerve at the back of the eye, pressing it in.
Glaucoma may not have any symptoms at first as it is usually first diagnosed at a routine eye test. So for those who do not have regular eye tests may not even realise they have it until glaucoma develops over a few years. The first thing you may notice is a loss to your peripheral vision, which could eventually lead to blindness if left untreated.
In rare cases glaucoma could develop rapidly and cause:
- Blurred vision
- Eye tenderness/ pain
- Migraines/ headaches
Who is at risk?
There are certain groups of people that are more at risk than others of developing glaucoma, such as:
- Those with close relatives with glaucoma
- Aged over 40
- Raised eye pressure
- Those of African, Caribbean and Asian origin
Early diagnosis and early intervention is paramount in helping delay the rate at which glaucoma progresses. For further information on glaucoma visit the NHS Choices