Anna Brouwer

Chapter 3 74 more frequently had a prolonged cone b-wave. 4 If FAs were performed on the same day as the ERG, there was at least an hour between the FA and ERG. 15 To determine whether cystoid macula oedema (CMO) was present, we used optical coherence tomography (OCT) (Zeiss, Cirrus HD OCT 5000) scans of the same day as the ERG. We defined an active uveitis as the presence of cells in the anterior chamber and/or a vitritis of ≥ 1+ cells and/or a fluorescein angiograms (FA) score of > 1. Statistical analysis For statistical analysis R version 1.1.456 (© 2009 - 2018 RStudio, Inc.) was used. ERG changes between the first and the follow-up ERG were investigated using the paired t-test or Wilcoxon paired sample test, depending on the distribution of data. Data distribution was evaluated with qq-plots, histograms and Shapiro Wilk test. All significances were two tailed. We considered p-values < 0.05 as statistically significant. Next, we investigated whether eyes that had a prolonged cone b-wave during the first ERG could improve, or worsen even more in the follow-up ERG. Also, we investigated whether eyes that had an implicit time that was within our reference values, could worsen in the follow-up ERG. These outcomes were then investigated in relation to clinical parameters using Pearson chi-square test or Fischer’s exact test for categorical variables, and a Student t-test or a Mann-Whitney-U test for continuous variables, depending on the distribution of data. For patient specific characteristics such as age, one eye per patient was analysed. For patients with a bilateral uveitis where both eyes had the same cone b-wave outcome (i.e. both uveitis eyes stable, improved, and worsened), one eye was selected at random. If the cone b-wave outcome differed between uveitis eyes of the same patients, the eye with the changed cone b-wave outcome (i.e. improved or worsened) was selected for analysis of patient-specific variables such as age or diagnosis. None of the patients had one eye which improved and one that worsened. Results ERG results Sixteen eyes of nine patients were excluded from further analysis, because the pupil size difference was > 1 mm between the two ERGs and a disparity in pupil size can cause a change in b-wave implicit time that is independent of retinal pathology. Of these excluded eyes, 2 eyes showed an improvement, 1 eye worsened and 13 eyes had no significant difference in the implicit time of the cone b-wave.