Anna Brouwer

ERG analysis The ERG was abnormal in 35 (56%) eyes (21 patients, 2 with unilateral uveitis) (Table 1). In line with this, when looking at the specific ERG parameters as continuous variables, uveitis patients did decidedly worse than healthy controls in all cone, 30Hz, rod and combined rod cone responses, with the exception of the rod implicit times (Figure 1 and Supplemental figures 1 - 7). The most frequently found ERG abnormality (24 eyes (38%)), was a prolonged implicit time of the cone b-wave, which was most pronounced at the lower stimulus strengths (0.3 and 1.0 cds/m 2 LA). In addition, responses showed abnormal waveforms with less steep slopes of both the ascending and descending limb of the b-wave (Figure 2). The second most frequently found ERG abnormality (21 eyes, 33%) was an abnormal 30 Hz flicker response, consisting of a reduction in amplitude, or a prolonged implicit time, or both (Figure 2). In 16 eyes (25%) both the implicit times of the cone b-wave were prolonged and the 30 Hz flicker response was abnormal. In 5 eyes the 30 Hz flicker response was abnormal, while the implicit times of the cone b-wave were within normal values, and in 8 eyes the 30 Hz flicker response was within normal values while the implicit times of cone b-waves were prolonged. No statistically significant differences were found in the b/a wave ratios of the cone ERG between uveitis and age matched controls. Besides abnormalities in the cone b-wave and 30 Hz responses, abnormalities in the rod (0.0001 - 0.01 cds/m 2 DA) and combined rod cone (3.0 - 30.0 cds/m 2 DA) responses were found in 8 eyes (13%) and 15 eyes (24%), respectively. Six eyes (10%) only had abnormalities in the dark-adapted ERG, without ERG abnormalities in the light-adapted ERG. Eyes with ERG abnormalities N (%) Overall 35 (56) Single flash cone a 27 (43) A-wave Amplitude 4 (6) Implicit time 2 (3) B-wave Amplitude 9 (14) Implicit time 24 (38) 30 Hz flicker response b 21 (33) Through Implicit time 7 (11) Peak Amplitude 17 (27) Implicit time 12 (19) Single flash rod c 8 (13) A-wave Implicit time 2 (3) B-wave Amplitude 6 (10) Implicit time 0 Single flash combined rod cone d 15 (24) A-wave Amplitude 11 (18) Implicit time 2 (3) B-wave Amplitude 7 (11) Implicit time 1 2) Abbreviations: ERG = electroretinography a) light adapted 0.3 - 10.0 cds/m 2 ; b) light adapted cone response; c) dark adapted 0.0001 - 0.01 cds/m 2 ; d) dark adapted 3.0 - 30.0 cds/m 2 Table 1: Electroretinogram abnormalities of uveitis eyes (n=63) 114 Chapter 5