We analyzed the OCT data from 57 eyes of 57 subjects (30 glaucoma subjects and 27 glaucoma-suspect subjects). The mean age was 63.1 (±14.9) years. There were 38 females. The study cohort included 53 Caucasian, 3 African-American, and 1 Hispanic patient. The mean RNFL thickness from the analysis provided by the manufacturer (Cirrus version 5.1; Carl Zeiss Meditec, Inc., Dublin, CA) was 77.8 (±14.1) microns. The mean rim area and average cup-to-disc ratio, as provided by the software (Cirrus), were 0.99 (±0.31) mm2 and 0.64 (±0.14), respectively. The Humphrey 24-2 mean deviation (MD) was −1.74 (±3.32) dB and mean pattern SD (PSD) was 3.19 (±3.22) dB.
Linear correlation between the macular RGC layer thickness and peripapillary RNFL thickness were examined across individual eyes. In particular, for each of the 66 local macular regions, a squared Pearson's correlation coefficient (
r2 ) was computed for each of the 12 local peripapillary regions. The peripapillary wedge representing the highest correlation was identified for display. For the correlation map, each of the 12 peripapillary wedge regions was assigned a separate color and each of the 66 macular regions was assigned the color of the peripapillary wedge representing the highest correlation. The resulting color-coded structure-structure correlation map and corresponding
r 2 values for each macular region are presented in
Figures 4A and
4B, respectively. The mean
r2 value across all local macular-peripapillary relationships was 0.49 (±0.11). The corresponding scatterplots, best-fit lines, and
r 2 values for all macular regions are presented in
Figure 5. In addition,
Figure 6 contains an enhanced color-coded map that illustrates, for each macular region, the set of peripapillary wedges with a Pearson's correlation coefficient not significantly different from that of the peripapillary wedge with the highest correlation.
The same correlation analysis was repeated for the 30 subjects with glaucoma (i.e., excluding the glaucoma-suspect subjects) and then separately repeated for the 27 subjects with glaucoma suspicion. In the glaucoma group (30 subjects), the mean
r 2 value across all local macular-peripapillary correlations was 0.56 ± 0.13, which was significantly larger than the mean
r 2 value in the glaucoma-suspect group (0.37 ± 0.11;
P < 0.001; paired
t-test). The corresponding color-coded correlation maps (along with illustration of peripapillary wedge sets with correlations not significantly different from that of the best wedge) for both cases are presented in
Figure 7. Note that in the glaucoma case (
Fig. 7A), for most macular regions, a smaller number of peripapillary wedges have a Pearson's correlation coefficient not significantly different from that of the best wedge when compared with the number present in the glaucoma-suspect case (
Fig. 7B) and the overall pattern more closely resembles expected nerve fiber bundle trajectories.
In addition, the analysis was repeated using both eyes of all subjects, with similar results (mean r2 value of 0.49 ± 0.11, data not shown). We also performed a similar correlation analysis between the macular nerve fiber layer (NFL) thickness and the peripapillary NFL thickness and found the correlations to be worse (mean r2 value of 0.40 ± 0.21, data not shown) than those from the macular GCL versus PP NFL thickness analysis.