The optic nerve and glaucoma

What is glaucoma?

Glaucoma is a group of conditions that damage the optic nerve, which carries signals from the retina to the brain. The exact cause of the most common types is not fully understood, but high eye pressure plays a part in many cases.

About half of people with glaucoma do not know they have it, because there are no early symptoms. Side vision fades slowly, often starting nearest the nose, and people may not notice until late.

The main types

• Open-angle: the most common type, slow and silent.
• Angle-closure: less common, and it can start suddenly as an emergency.
• Normal-pressure: the nerve is damaged even though pressure is in the normal range.
• Congenital: a less common type.

An acute attack is an emergency

Severe eye or forehead pain, redness, sudden blurred vision, headache, nausea and vomiting, and coloured halos around lights can mean an angle-closure attack. Do not wait for an appointment. Go to the emergency department or an eye doctor at once.

Who is at higher risk?

• Age over 40, with the risk rising further with age
• A family history of glaucoma
• High eye pressure
• Short or long sight
• A past eye injury
• Long-term steroid use
• Thin corneas
• Diabetes, migraine and high blood pressure

Which tests diagnose it?

A pressure reading alone is not enough. A full exam usually includes:

• Eye pressure measurement
• A check of the drainage angle (gonioscopy)
• A look at the optic nerve by examination, photograph or OCT
• A visual field test of side vision
• A measurement of corneal thickness

Treatment

Treatment aims to lower the pressure and protect the sight you have:

• Drops: usually the first treatment, and they must be used every day.
• Laser: depending on the type, it improves drainage or makes a tiny hole in the iris.
• Surgery: when drops and laser are not enough, a new drainage path or a drainage tube is created.

Once you start medicine, follow-up visits are typically every 3 to 6 months. These visits are part of treatment, because the disease is silent.

To learn how to put in drops properly, see the patient guide.