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These articles will be changed regularly and cannot be reproduced without the prior consent of Glaucoma Australia Inc. Click here to return view previous Articles of the Month index page The following item, slightly modified, appeared in Glaucoma News, Autumn 1998 issue Field Test The telephone at Glaucoma Australia rings and a rather anxious voice tells us " I’ve just found out that I have glaucoma, and my specialist wants me to have a field test. What is it? Is it painful? Will I be able to do it? I’m 73 and not very active." Those of us with longer experience of glaucoma are very familiar with field of vision tests, which we usually do once or twice a year. We are quite used to being sat down in front of a Humphrey or another brand of computer that monitors the test and then prints out the results in chart form so that the ophthalmologist can judge whether our field of vision has remained stable. If it has, this indicates that our treatment is controlling our pressures satisfactorily. If we have lost a little more vision, then other treatment must be prescribed. Each eye is tested separately. A Humphrey chart looks like the example shown here. The darker areas are those where sight has been lost. Lighter shading indicates partial loss of sight. We all have a normal blind spot in our eyes, and this is circled on the chart. When we do a field test, we look into an illuminated white bowl, with our chin supported on a rest, a patch over one eye, and we stare fixedly at a spot in the centre of the bowl. While keeping our eye firmly fixed on this spot, we press a little button whenever we see a spot of light flashing very briefly anywhere in the bowl. We see this with our peripheral vision, which is the first part of our sight to be affected by glaucoma. We need good concentration to keep our eye fixed on the central spot and not to let our gaze wander round the bowl as the little light flash. The computer knows when our eye wanders and disallows any button-press when we see light this way. Very few of us enjoy a field test. It is not painful in any way, but most of us find it a strain and we are anxious that we will do it badly – that we might press the button at the wrong time when we have not really seen a light, or miss pressing the button when we have. The computer allows for all this – it recognises a "false positive" and because it goes over the same area more than once, we are given a second chance to record seeing a light in the area we missed before. But we always have a sense of relief when the test is over! The good news for field-haters is that new equipment is coming along and you should find the tests are quicker
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