To further explore the impact of the severity of baseline damage on detection of structural worsening, we stratified the pooled superpixels as a function of their corresponding baseline TD values (
Fig. 6). The detection rates decreased with increasing baseline glaucoma damage for GCL, GCIPL, and GCC. Among these three measures, GCC had the highest detection rates along the spectrum of glaucoma severity, and the difference was significant regardless the severity when compared to GCL (Tukey test:
P < 0.001,
P = 0.004, and
P = 0.034 for TD values of > −6, −6 to −12, and <−12 dB, respectively); in contrast, there was no significant difference between GCC and GCIPL along the entire spectrum of 10-2 VF severity (
P ≥ 0.38, Tukey est). There was a significant difference between GCL and GCIPL only in superpixels with the least severe baseline VF damage (Tukey test:
P <0.001,
P = 0.25, and
P = 0.97 for TD values of > −6, −6 to −12, and <−12 dB, respectively). Among all five macular measures of interest, FMT had the highest detection rate (
P < 0.001 for all comparisons, except versus ORL at SPs corresponding to VF test locations with moderate [
P = 0.019] and severe [
P = 0.25] baseline damage, Tukey test), and its detection rates did not exhibit any significant trend as a function of disease severity. The proportion of superpixels with worsening of ORL increased with glaucoma severity (
P < 0.001, Tukey test). FDRs were uniformly low for all macular measures, and there was no significant difference within the same macular measure along the entire spectrum of disease severity (
P = 0.08 or above, Tukey test), except when comparing GCC FDRs for the least and most severe TD severity groups (
P = 0.003, Tukey test).
Figure 7 shows the normalized rates of change of each macular measurement stratified for the baseline TD values. The normalized rates of change for GCL, GCIPL, and GCC became slower (less negative) as the severity of damage increased (
P < 0.001) and reached 0%/year in locations where the baseline TD was worse than −12 dB. The variability of rates of change was highest for GCL regardless of the baseline TD values. The normalized rates of change of FMT and ORL were similar at the locations with moderate and severe TD damage (
P = 1.0 and
P = 0.9, Tukey test), whereas the ORL had significantly slower rates of change for locations with a mild baseline VF damage (
P < 0.001, Tukey test). The normalized rates of change did not considerably change with disease severity for FMT (
P = 0.99), whereas they became slightly faster with advancing disease severity for ORL (
P < 0.001).