Anna Brouwer

procedures. Therefore, it is useful to see if the same results can be obtained in a large cohort of patients, who may be scared or photophobic which makes the recording of an ERGmore difficult. Also, a larger group can yield more reliable confidence intervals of differences between the two DTL positions. The aim of this study was to determine the optimal DTL electrode position for monitoring purposes. We investigated whether one DTL position yields more stable ERG results than the other. If such a difference is found, this would imply that this DTL electrode position should be used for monitoring purposes. We compared the reliability as well as the relative variability of the results and investigated differences in amplitudes and implicit times. Methods Subjects The subject population, consisting of 200 patients (355 uveitis eyes, 45 unaffected eyes) with a non-infectious uveitis, aged ≥ 18 years (median 53.4, IQR 39.2 - 63.7), has been previously described. 18 All patients were mentally competent and gave their written consent to participate. This study was conducted in compliance with the ethical principles of the declaration of Helsinki. Ethical approval was requested and obtained from the Medical Ethical Research Committee of the University Medical Centre Utrecht. ERG measurement All ERGs were measured according to the ISCEV standards. 8 An Espion E3 system with Colordome stimulator (Diagnosys LLC, Cambridge, UK) was used for full-field flash stimulation. Eyes were anesthetized with oxybuprocain 0.4%. Pupils were dilated with tropicamide 0.5%. Cup electrodes were used as ground and reference electrodes and placed on the forehead and on the temples. Impedances of reference and DTL electrodes were below 5 kΩ and below 10kΩ for the ground electrode. Figure 1: Representative example of the two Dawson, Trick, Litzkov (DTL) positions that were used: the lower lid position (LLP) (left) and the fornix position (FP) (right). 142 Chapter 7