Anna Brouwer

Two clinical parameters were statistically significantly different between eyes with and without these ERG abnormalities in both the analysis using all uveitis eyes, and the analysis using only one eye per patient. These were: CME and 3+ vitreous cells (Table 2). There was no significant correlation between these two variables (Spearman’s rho correlation coefficient = 0.259; p = 0.056). No statistically significant differences were observed between the two groups with regard to treatment, or in the inflammation activity on FA score. Interestingly, we also found no statistical differences in BCVA, which was relatively good in both groups (0.05 and 0.05 LogMAR) (Table 2). Furthermore, no statistically significant differences were observed between clinical parameters and rod and combined rod- cone abnormalities. Discussion In this study, more than half of the eyes with non-anterior childhood uveitis showed ERG abnormalities. The light-adapted ERG was most frequently affected, showing a prolonged cone b-wave implicit time, particularly at lower stimulus strengths, and abnormal 30Hz flicker responses. Two clinical parameters were statistically significantly associated with these ERG abnormalities: CME and 3+ vitreous cells. All eyes with CME had abnormal cone ERGs. Although cones are densely packed in the macula, 15,16 macular dysfunction alone contributes only minimally to the full field cone. 17–19 The abnormal ERG in the children with CME therefore indicates a global retinal dysfunction and not only macular dysfunction. 18 A correlation between visual acuity and outer retinal function (represented by the a-wave) has been described, which is in line with our study in which we found a relatively good visual acuity and few a-wave abnormalities. 20,21 However, a correlation between visual acuity in inner retinal function (represented by the b-wave) as found in birdshot uveitis, was not confirmed in our study on childhood uveitis. 22 This discrepancy between birdshot and childhood uveitis may be due to a disease-specific inflammatory mechanism or to the duration of disease. Besides eyes with CME, all eyes with 3+ vitreous cells also showed ERG abnormalities, indicating that more severe inflammation frequently results in retinal dysfunction. The prolonged b-wave implicit time and the abnormal 30 Hz flicker response indicate an abnormal inner retinal transmission dysfunction from photoreceptors to bipolar cells. 18 This abnormal signal transmission could be caused by an increased interneuronal distance secondary to an increased permeability of the blood-retinal 118 Chapter 5