Anna Brouwer

reflect the conditions of clinical practice more accurately than a study with healthy volunteers who are frequently familiar with the proceedings. However, it is important to note that uveitis patients have a great intra-individual variability, ranging from normal to almost absent responses. 18 This explains why the ranges from this study are relatively large and often not normally distributed. That being said, we believe that the conclusions drawn from this study can be extrapolated to other populations, because we tested both DTL positions in the same patient and compared these with each other. A limitation of this study is that the LLP was always measured first and the FP second. Alternating between these two positions at random would have been preferable to correct for a possible unknown bias. Since our reference values were measured with the LLP, we wanted to make sure we first obtained an ERG which was compliant with our reference values, before measuring other ERG results. Also, in future studies it would be interesting to measure the ERG twice in the FP and twice in the LLP. This would give an even better indication of the amount of variability between the two positions. In summary, we conclude that neither DTL position is preferred above the other when monitoring patients. When clinicians choose a DTL position for new reference values, they must decide whether they prefer larger responses or greater patient comfort. But above all, it is important to check the DTL position during an ERG measurement and to ensure that the DTL position is the same as in earlier measurements of the same patient. Acknowledgements Wewould like to thank all patients for participating in the study.We thankN.H. tenDam, R. Wijnhoven, J. Ossewaarde-van Norel and L. Ho, for their help in requiting patients to participate in this research. We thank D. Gültzau, Y. Burgers, and M. Ballast for their help in recording the ERGs and H. Talsma for giving additional electrophysiological advice. We thank P. Zuidhof and S. Risseeuw and for their statistical advice. Compliance with Ethical Standards: This study was supported by the following foundations: Dr. F.P Fischer Stichting and Bartiméus Fonds that contributed through UitZicht. The funding organizations had no role in the design or conduct of this research. They provided unrestricted grants. A.H. Brouwer received an Association for Research in Vision and Ophthalmology (ARVO) international chapter affiliate travel grant. G.C. de Wit is employed as a medical 150 Chapter 7