Significant structural parameter changes (
P < 0.005) between IOP 10 mm Hg/30 minutes and IOP 45 mm Hg/60 minutes (
Table 2) were observed for neuroretinal rim measurements (RW and RV, both decreasing), RNFLV (decreasing), PLTT (decreasing), ALCS depth
BM.(increasing), and NCO depth (increasing). There were no significant changes in structural parameters generated from the volumes evaluated in the control experiment (IOP 10 mm Hg/10 minutes compared with IOP 10 mm Hg/30 minutes;
Table 3).
Table 4 shows the change in each parameter for each eye compared between IOP 10 mm Hg/30 minutes and IOP 45 mm Hg/60 minutes.
Table 5 shows the change in each parameter for each of the six eyes included in the control experiment.
Marked decreases in RW (expressed as percentage of baseline value, percentage SD; −11%, 2%), RV (−15%, 5%), and PLTT (−12%, 5%) were observed, as were considerable increases in NCO depth (65%, 25%) and ALCS depthBM (20%, 8%). The amount of change observed in RNFLT, RNFLV, and NCOarea with elevated IOP was in each case negligible, amounting to a mean of 2% or less in either direction, which was equivalent to what had been observed for those parameters in the control experiment. Although a higher percentage change was detected for ALCS depthNCO with IOP elevation (5%, 6%), this change was within the interscan variability observed in the control experiment (−1%, 8%).
Figure 1 illustrates the relationship between the change in NCO depth and the change in prelaminar tissue thickness (left) and the change in RV (right) for the 10 acute IOP elevation eyes and the six control experiment eyes. In both cases, there was a clear association between the change in each parameter and the magnitude of NCO depth change (
R 2 = 0.49 for change in prelaminar tissue thickness,
R 2 = 0.41 for change in RV for the 10 eyes with acute IOP elevation). Images obtained from the eye with the most profound changes associated with acute elevation of IOP (right eye of animal 21808) are shown in
Figure 2. The delineated structures at 10 mm Hg/30 minutes (
Fig. 2A) and at IOP 45 mm Hg/60 minutes (
Fig. 2B) are overlaid using the NCO reference plane (
Fig. 2C) and using the secondary peripheral Bruch's membrane reference plane (
Fig. 2D). An obvious posterior movement of the ILM is seen using the NCO reference plane, whereas the posterior movement of the ALCS is clearly present but less striking. When the secondary reference plane is used, the posterior movement of both the ILM and the ALCS is increased, and the posterior movement of Bruch's membrane is also seen. When examining individual eye change, only two eyes demonstrated a substantial increase in ALCS depth relative to NCO (40 μm observed for animal 21808 OD, as illustrated in
Fig. 2, and 21 μm observed for animal 25340 OS). In both cases, the increase in ALCS depth
NCO exceeded the maximal change observed for that parameter in the control group (19 μm.)