ERG recordings from control and moxifloxacin-injected mouse eyes are shown in
Figure 1 .
Figure 1Ashows scotopic b-wave responses to increasing intensities of flashed light. The scotopic b-wave is a measurement of the extracellular field potential that primarily arises from rod bipolar cells in response to dim flashes of light.
23 The relationship between scotopic b-wave amplitude and intensity can be modeled with a hyperbolic saturation (Naka-Rushton) function. This model yields two parameters,
b max,scot and
I 0.5, representing the maximum b-wave amplitude and the intensity that provides half saturation, respectively. As shown in
Figure 1A , scotopic recordings from control eyes demonstrated a progressive increase in b-wave amplitude with increasing intensity of light. The maximum b-wave amplitude in control eyes was 530 ± 55 μV and the half-saturation intensity measured 1.9 ± 0.2 φ/rod. The b-waves measured from eyes injected with various concentrations of moxifloxacin demonstrate similar morphology and amplitude. There was no statistically significant difference in
b max,scot or I
0.5 between control eyes and any of the groups of moxifloxacin-injected eyes
(Table 1) . Significance was measured with both the Student’s
t-test (two-tailed, assuming equal variance) and ANOVA.
Figure 1Bshows the ERG response to an intense flash that saturates the rod photoreceptors. The saturated scotopic a-wave from control eyes measured 690 ± 25 μV. Once again, there was no significant difference between control eyes and those injected with moxifloxacin
(Table 1) . To determine cone function, photopic ERGs were measured in the presence of a rod-saturation background
(Fig. 1C) . For control eyes,
b max,phot measured 190 ± 40 μV and
a max,phot measured 75 ± 15 μV. Again, there was no significant difference in the photopic response measured from control eyes and moxifloxacin-injected eyes
(Table 1) .
Similarly, ERG recordings were performed in rabbit eyes before and 4 weeks after moxifloxacin injection. Scotopic b-wave responses to increasing intensities of flashed light
(Fig. 2A) , saturated scotopic a-wave
(Fig. 2B) , and photopic recordings
(Fig. 2C)were measured before (left) and after (right) moxifloxacin injection. Scotopic
b max was 397 ± 54 and 408 ± 23 μV, and
I 0.5 was 9.4 ± 0.6 and 9.1 ± 0.7 φ/rod, before and after moxifloxacin injection, respectively. Scotopic
a max was 199 ± 17 and 177 ± 54 μV; photopic
b max was 192 ± 12 and 177 ± 13 μV, and photopic
a max was −94 ± 5 and −85 ± 3 μV, before and after moxifloxacin injection, respectively. Again, statistical analysis showed no significant difference between the pre- and postinjection groups in any of the scotopic or photopic recordings
(Fig. 2) . Thus, ERG studies show no evidence of retinal functional change in either the mouse or rabbit model after intravitreal moxifloxacin injection of any concentration groups tested in this study.