World Glaucoma Week: what a screening finds

World Glaucoma Week falls in the second week of March, and the chapter's zones run public screening around it. Attendance is free and open. This is what the session involves and what you should take away from it.

Why a screening week exists at all

Glaucoma causes no symptoms until it has taken a substantial amount of sight, and what it takes does not come back. There is no discomfort to prompt a visit and no blurring to notice. The only way it is caught early is by looking for it in people who feel perfectly well — which is a difficult thing to organise, and the reason a week is set aside for it.

The disease is more common in people of African descent, tends to start earlier, and tends to progress faster. It is among the leading causes of irreversible blindness in Nigeria.

What is checked

Intraocular pressure. Quick and painless. Raised pressure is the main treatable risk factor.

The optic nerve head. Examined directly, and the most informative single observation — the proportion of the nerve that is cupped, the shape of what remains, and whether the two eyes differ from each other.

Visual field, where indicated. This maps peripheral sensitivity and finds losses the brain has been filling in.

The drainage angle, to distinguish open-angle from angle-closure disease, which are managed differently.

History: family history above all, plus diabetes, long-term steroid use, previous eye injury, and high short-sightedness.

What the pressure number does not tell you

This is the most important thing to take away from a screening.

A normal pressure does not mean you do not have glaucoma. A significant proportion of glaucoma in African populations occurs at pressures within the normal range — normal-tension glaucoma — and a screening that measured only pressure would miss it entirely. This is why the optic nerve is examined and why a pressure check alone is not a glaucoma screening.

Equally, a single high reading does not mean you have glaucoma. Pressure fluctuates through the day, corneal thickness affects the measurement, and plenty of people have raised pressure with a healthy nerve. It means you need a fuller assessment, not that you have the disease.

What happens if something is found

You will be referred for a full examination — the screening is a filter, not a diagnosis. Diagnosis requires repeated measurements, formal visual fields, and often imaging of the nerve fibre layer.

If glaucoma is confirmed, treatment is usually drops to lower the pressure, with laser and surgery available where drops are insufficient. Treatment protects what you have; it does not recover what has gone. That asymmetry is the entire argument for being screened before you notice anything.

Who should come

Anyone over forty. Anyone over thirty-five of African descent. Anyone with a parent or sibling who has glaucoma, at any age. Anyone with diabetes, anyone who has used steroid medication long-term, and anyone who has had a significant eye injury.

If you have been told in the past that your pressures were "a bit high" and nothing came of it, come. That is exactly the group worth re-examining.

Dates and venues

Each zone announces its own venue and times. Details appear on this site's events page as they are confirmed, and through the zonal secretaries.