What is glaucoma
Glaucoma is a chronic disease of the optic nerve. Its main risk factor is eye pressure that is too high for that eye. Understanding how it works is the first step to recognising it in time.
The optic nerve can be compared to a transmission cable that connects the retina to the brain. It is made up of a bundle of threads called nerve fibres, more than a million for each eye.
The point where this cable meets the back of the eye is called the optic disc. The health of the optic disc depends on the circulation of blood and nutrients, which slows down and is hindered when eye pressure becomes too high.
Each nerve fibre carries part of the visual message from the retina to the brain, where images of the surroundings are put together. The 'visual field' is the part of our surroundings within which we can perceive images without moving our gaze.
- What it affects
- The optic nerve — more than a million nerve fibres for each eye.
- Main risk factor
- High eye pressure, which hinders blood flow to the optic disc. Damage can also occur with pressure in the normal range.
- Key feature
- Progressive and irreversible: damage to nerve fibres does not recover.
- Early symptoms
- Often none — the disease has no symptoms until the advanced stages.
How it progresses
When the fibres of the optic nerve begin to be damaged, areas appear in the visual field where you can no longer see — called scotomas. Initially very small, they are only noticed when they become large and the damage is already considerable.
The glaucoma trap
Meanwhile, the patient will continue to see clearly in the centre. In the final stages the optic nerve is completely destroyed and the patient becomes blind. That is why it is essential to detect glaucoma in time.
The different types
There is not just one type of glaucoma: the disease takes different forms depending on its origin, how quickly it progresses and how it is treated. Recognising them is essential to choosing the right treatment strategy.
- 01
Chronic open-angle glaucoma
The most common formAlso known as primary open-angle glaucoma, it is the most common type and is linked to a sort of ageing of the drainage filter: the ability to reabsorb aqueous humour slowly decreases over the years and the pressure inside the eye rises.
The drainage angle remains open, but the filter works progressively less well. In Europe it is the most common form of glaucoma in adults.
Unfortunately, this form can damage sight gradually and insidiously, to the point of causing very serious damage before it is recognised. In some cases glaucomatous damage progresses even though the intraocular pressure appears to be within normal limits. Managing these cases of normal-tension glaucoma can be difficult.
- 02
Angle-closure glaucoma
Acute attackAngle-closure glaucoma is caused by an obstruction of the drainage angle, which closes as if a sheet of paper floating in a sink came to rest right over the plughole, blocking it completely.
In the eye, the iris can behave like the sheet of paper: it presses against the cornea, completely closing off the flow of aqueous humour towards the angle. Usually this happens slowly but, if it happens suddenly, it is called an acute attack of glaucoma.
Normal drainage vs closed, blocked angle Symptoms of an acute attack
- Seeing coloured haloes around lights
- Intense eye pain
- Blurred vision
- Headache
- Nausea and vomiting
- 03
Congenital glaucoma
In childrenVery rarely, glaucoma can appear at birth or in early childhood. In these cases the drainage angle is abnormal from birth. These cases need highly specialised management.
Usually noticed
- Enlargement of the eyeball
- Cloudiness of the cornea
- Watering of the eyes
- Tendency to close the eyes in bright light
- 04
Secondary glaucoma
Specific causesSecondary glaucoma is caused by specific factors such as: trauma, medication, tumours, inflammation and circulatory abnormalities.
Eye pressure rises because the fluid drainage system is damaged. In these cases treatment can be very complex.
Why early diagnosis is crucial
Glaucoma is often called 'the silent thief of sight' because it can progress without obvious symptoms until the damage is already significant. Once the visual field has been compromised, it cannot be recovered.
Regular eye check-ups after the age of 40 — or earlier if you have risk factors — are essential to detect glaucoma in its early stages, when treatment is most effective at preserving sight.