High eye pressure does not always mean an operation

Your eye makes fluid all day and drains it away. If the drain is slow, pressure builds up and squeezes the optic nerve — the cable that carries pictures to your brain. Damaged nerve fibres do not grow back, so the goal is to stop further loss.

Side vision goes first, and you will not notice it. That is why the tests matter more than how you feel.

• Pressure reading. One high number on one day is not glaucoma. Doctors look at several readings.
• Visual field test. The button-pressing test with flashing lights. It maps the side vision you have already lost.
• OCT of the nerve. Measures how thick the nerve layer is. Repeated over years, it shows whether things are getting worse.

One test alone rarely decides anything. The trend over time decides.

1. Eye drops, once or twice a day. For most people this is enough for many years.
2. Laser to open the drain. A short outpatient procedure, no cutting.
3. Surgery to make a new drainage path, when drops and laser are not holding the pressure.

Surgery is a real and sometimes necessary step. But if you have not properly tried drops, or nobody has checked whether you are using them correctly, ask why you are skipping ahead.

• Pressure stays very high despite maximum drops.
• Field tests show loss getting worse visit after visit.
• A sudden painful attack with red eye, headache and vomiting. Go to hospital now.
• A child born with glaucoma.

• Ask to see your field test and OCT from last year next to this year's.
• Ask which drops you have tried, and for how long.
• Ask what the surgery aims to prevent, and what it cannot bring back.
• Keep every printout. Old reports are the most valuable thing you own here.