Structural and functional imaging of the retina: new ways to diagnose and assess retinal disease

This paper describes optical coherence tomography (OCT) and the multifocal electroretinogram (mfERG), two recently available examination modes. Some of the limitations and disadvantages of using the techniques are discussed. The utility and scope of the techniques in diagnosis and assessment of some aspects of glaucoma are compared. OCT provides structural information and is fast, requiring no preparation of the patient; the output is immediately available. Current measurements of macular or peripapillary thickness provide useful quantitative data to assist in diagnosis and in monitoring the progress and any treatment of eye disease. New outputs may provide more sensitive methods of diagnosis than those currently available but it is important that such methods are carefully validated. mfERG takes longer to perform than OCT, requires preparation of the patient and the output may not be immediately available. Some outputs are complex and may require expertise in interpretation, which is not available to the average practitioner. Typically, mfERG systems are available only in specialist centres where research is carried out and where patients are referred for evaluation. It is likely that the procedures of the mfERG are so time consuming and complex that they will never reach the level of the general practitioner. Many mfERG protocols have not been widely used and there is scope for application of these protocols in spatial, temporal and contrast domains to improve the way in which they discriminate normal from abnormal visual systems. Until protocols have been standardised and their use is widespread, the findings from such reports should be viewed with a degree of caution. Currently, OCT is more widely accepted and more useful than the mfERG for evaluation of glaucoma and a wide range of other ocular defects.