Visual fields assessment is pretty well universal in optometric practice and serves as a useful indication of retinal function. It is, however, reliant upon subjective responses and only capable of detecting retinal damage after a significant percentage of cell death. Any objective test for retinal and visual pathway should be of interest to all. Historically, electrophysiology has been used this way but, as many ex-pupils of Aston may remember from Professor Graham Harding’s lectures, if the hairnet of electrodes does not put you off this as an easily applied technique, then the differentiation of small fluctuations on the variously lettered output waves will.
However, improved techniques have now allowed much easier application of electrophysiological testing and rapid assessment of electroretinograms (ERG) and visually evoked responses are now possible and increasingly being used in primary care optometry in the US. One company has developed a simple electrode that is positioned on the face below the lower lid and allows a two-minute pattern ERG to be measured and displayed as a curve, deviations from which can easily be detected as showing the impact of ganglion cell functional loss. They also have a visually evoked potential unit similarly able to quickly detect visual pathway deficit. As well as providing a rapid, and importantly, objective assessment of retinal or pathway function so helping to screen for glaucoma and maculopathy detection, the units are also finding great use in other areas, such as assessing retinal function prior to cataract extraction or monitoring the impact of systemic drugs such as chloroquine or tamoxifen.
The company is looking to expand its operation into Europe and I very much hope to be able to report further on this interesting development. I have to say that, on first viewing, I think this area will have a big impact on optometry in the coming years.
Watch this space.
