Features

If you are lucky enough to find yourself in Sydney at some point, and you haven't quite closed your mind to all things optometric, try this simple glaucoma test.

After coming out of the Opera House, gaze across at the Harbour Bridge. Close your left eye and fixate on the left hand pillar. You will notice that the right hand pillar disappears from view. Similarly, close the right eye (and open the left) and the left pillar will disappear when looking at the right one.

You will then notice that the arc of the bridge falls neatly across the inferior retinal arcuate fibres (the image being inverted on the fundus).

Next, you will need a fixation target. It won't be long before a ferry comes out from Circular Quay across the harbour on its way to Luna Park on the other side of the bridge. As it makes its journey, use it as your moving fixation target and you will be able to check whether you have any signs of an arcuate scotoma in the superior field, at several points from fixation.

Observe whether the bridge fades or breaks up at any time, hopefully it won't, and your arcuate fibres are intact.

As the sensitivity of the tests improves with reduced illumination, you may need to linger a while with a glass of chardonnay towards the evening, purely in the interests of accuracy.

Unless you have a strong personality, it is not recommended that you check the inferior field in the obvious way.

Although this is a relatively expensive glaucoma test for UK residents, it is well worth the expense. It is, unfortunately, unavailable with NHS funding. I hope to have a downloadable record sheet available in the New Year.

● Graham O'Regan is a practising optometrist in Gloucestershire

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