Glaucoma—1: Diagnosis

doi:10.1136/bmj.328.7431.97

From trainee to consultant, BMJ Group offers doctors around the world tailored information, special events, learning resources and recruitment services at every step along their career path.

... by doctors, for doctors, for patients
We are open for entries!

Online learning

BMJ Learning

High-quality CME / CPD for doctors and other healthcare professionals. BMJ Learning features hundreds of accredited, peer-reviewed learning modules in text, video, and audio formats. Find out more

Courses and Qualifications

BMJ Masterclasses

BMJ Masterclasses, led by experts, help clinicians to use the latest evidence and recent guidelines in practice and meet their CPD/CME requirements. Find out more

Exam Preparation

The leading provider of online exam preparation, helping over 167,000 healthcare professionals to pass their exams. Find out more

onExamination

Search all BMJ education articles:

From

Limit by

The BMJ iPad app brings you the best of print and online, including live links to the latest news, blogs, video, and podcasts. Get the BMJ iPad app.
You can use bmj.com to help you with your continuing medical education. Find out about CME/CPD credits for BMJ articles
Keep up to date with cardiology: Access the latest cardiovascular medicine resources from across BMJ Group.
Countdown to London 2012: BMJ Group's Olympics portal highlights latest Olympics and sports medicine-themed research, comment and learning

This article has a correction

Please see: ABC of Eyes

Access to the full text of this article requires a subscription or payment. Please log in or subscribe below.

P T Khaw,
A R Elkington

Introduction

The glaucomas are a range of disorders with a characteristic type of optic nerve damage. The glaucomas are the second commonest cause of blindness in the world, and the commonest cause of irreversible blindness. The most effective way of preventing this damage is to lower the intraocular pressure.

Normally, the ciliary body secretes aqueous, which flows into the posterior chamber and through the pupil into the anterior chamber. It leaves the eye through the trabecular meshwork, flowing into Schlemm's canal and into episcleral veins. The flow and drainage can be obstructed in several ways.

Normal aqueous drainage and possible sites of obstruction

Symptoms and signs

Raised intraocular pressure

The intraocular pressure is determined by the balance between aqueous production inside the eye and aqueous drainage out of the eye through the trabecular meshwork. Each normal eye makes about 2 μl of aqueous a minute—that is, about 70 l during the course of a lifetime. Normal intraocular pressure is 10-21 mm Hg, but it can drop as low as 0 mm Hg in hypotony and can exceed 70 mm Hg in some glaucomas.

The rate at which raised intraocular pressure causes optic nerve damage depends on many factors, including the pressure and whether glaucomatous damage is early or advanced. In general, pressures of 20-30 mm Hg usually cause damage over several years, but pressures of 40-50 mm Hg can cause rapid visual loss and also precipitate retinovascular occlusion.

Haloes around lights and cloudy cornea

The cornea is kept transparent by the continuous removal of fluid by the endothelial cells. When the pressure rises quickly (acute closed angle glaucoma), the cornea becomes waterlogged, causing a fall in visual acuity and creating haloes around lights (like looking at a light through frosted glass).