The reduction of IOP by >25% or to a predetermined target IOP in glaucomatous and OHT eyes (IOP reduced group, 18 eyes) significantly increased the PhNR amplitude by a mean +5.9 ± 2.4 μV (from 11.5 ± 1.7–17.4 ± 1.9 μV, mean 51.8% increase,
P = 0.023) and +5.3 ± 2.3 μV (from 13.2 ± 2.1–18.5 ± 2.4 μV, mean 40.2% increase,
P = 0.035) at 2.25 and 3.00 cd.s/m
2 stimulus intensities, respectively (
Table 4). An example of the improvement in PhNR amplitude following reduction of IOP is shown in
Figures 4A,
4B. The reduction of IOP also increased the PhNR/b-wave amplitude ratio by a mean +0.065 ± 0.026 (from 0.121 ± 0.020–0.186 ± 0.018 μV, mean 53.8% increase,
P = 0.023) and +0.051 ± 0.016 (from 0.135 ± 0.020–0.187 ± 0.020 μV, mean 37.7% increase,
P = 0.0046) at 2.25 and 3.00 cd.s/m
2 stimulus intensities, respectively (
Table 4,
Fig. 5). There was no significant change in a-wave (
P = 0.25 and
P = 0.44 for 2.25 and 3.00 cd.s/m
2 stimulus intensities, respectively) and b-wave (
P = 0.89 and
P = 0.72 for 2.25 and 3.00 cd.s/m
2 stimulus intensities, respectively) amplitudes following reduction of IOP. In addition, we found a significant correlation between the degree of reduction in IOP and the magnitude of increase in PhNR/b-wave ratio at the 2.25 cd.s/m
2 stimulus intensity (
r = 0.429,
P = 0.020,
n = 29,
Fig. 6A) and at the 3.00 cd.s/m
2 stimulus intensity (
r = 0.544,
P = 0.0023,
n = 29,
Fig. 6B) after the outlier with a 52 mm Hg reduction in IOP was excluded.