Glaucoma is a very well known illness of the eyes. A visit to the optician often involves a check on the pressure within the eye (intraocular pressure (IOP)). This has been the standard test for glaucoma for years. Unfortunately once there are symptoms, damage will often already have been done to the eyesight. That damage can include blindness and it accounts for 7% of new registrations of visual disability.
IOP increases during the acute phase but 8 - 10% of people over 40 will have pressure in the eyes over the conventional danger limit of 21 mmHg. By no means all will go on to develop glaucoma. Of great concern is that this screening method leads to over-diagnosis and possible harm from over treatment. It is said that glaucoma and more particularly suspected glaucoma accounts for the sixth largest share of NHS outpatient attendances and therefore almost certainly over use of resources.
A recent paper in the British Medical Journal (Glaucoma and Intraocular Pressure in EPIC – Norfolk Eye Study by Chan and others) reviewed the pressure in 8401 pairs of eyes in patients over 48 in Norfolk. It identified a large number of people with raised ocular pressure and suspected glaucoma. It also found that there were many with confirmed glaucoma, but with pressure below the threshold figure of 21 mmHg.
The conclusion was that IOP is a very weak marker for the detection of glaucoma. Those with raised pressure should be monitored regularly but other markers such as age, African or Asian descent, and those with a first degree relative with glaucoma should also be considered. An optical CT scan can be performed but the cost is very high and the process not sufficiently evaluated. Testing of the functioning of the optic nerve has also been proposed but has been found to be not sufficiently sensitive for detection of glaucoma.
Therefore no adequate screening test presently exists but it has been suggested that a better way forward would be to routinely screen for the four main eye diseases. Those include glaucoma, cataract, age-related macular degeneration and diabetic disease of the retina. The test for one will often show up signs of another and it would clearly be efficient to carry out all four sets of tests at the same time, not only for the benefit of the clinician but also for the patient.
Tim Wright, senior associate in Penningtons Manches’ clinical negligence team, comments: “We welcome proposals to introduce a more streamlined system of eye testing. A change in methods of diagnosis is likely to lead to more accurate results, earlier treatment and saving more people from blindness.”