Table 1 shows that the patients did not differ in age or sex from the volunteers, but the refractive power and intraocular pressure were significantly higher in the SGPPG eyes than in the healthy eyes.
Among the SGPPG eyes, 13 had localized rim thinning and the rest (17 eyes) had diffuse rim thinning. The localized rim thinning was detected within the 7-o'clock sector in 10 eyes, 6-o'clock sector in two eyes, and 12-o'clock sector in one eye. Seven (23.3%) of the 30 SGPPG eyes had NFL defects on the color or red-free fundus photographs. All these defects were located between the 7- and 8-o'clock sectors. The center of the NFL defects at the disc margin was located within the 7-o'clock sector in six (85.7%) eyes and within the 8-o'clock sector in one (14.3%).
Figure 2 shows maps of the average IRL thickness of the SGPPS and healthy eyes, and
Figure 3 shows a fractional deviation maps.
Table 2 shows the mean thickness in various macular areas (macular subfields) of the total retina, IRLs, and macular NFL in the healthy and SGPPG eyes; all three layers were significantly thinned in the outer ring (3–6 mm from the foveal center) and in the outer ring of the inferior hemisphere in the latter group. The IRLs were also significantly thinned in all but the inner ring, either for the whole macula or just the superior or inferior inner hemicircular sector.
Table 3 shows the mean thickness of the total retina, IRLs, and macular NFL in the healthy and SGPPG eyes in each sector of the GSC. All three layers were significantly thinner in the SGPPG eyes in the inferior nasal outer and inferior temporal outer sectors, and all layers but the NFL were significantly thinner in the superior temporal outer sector.
Table 4 shows mean thicknesses in the macula of the total retina, IRLs, and NFL in healthy eyes and eyes with SGPPG in each sector of the ETDRS chart. All four layers were significantly thinner in eyes with SGPPG only in the inferior outer sector. In addition, they were significantly thinned in the superior outer sector (total retina, NFL) or temporal outer sector (total retina, IRLs). The IRLs were also thinned in the inferior and temporal inner sectors, and the IRLs and NFL were thinned in the nasal outer sectors.
The cpNFL was significantly thinner in the SGPPG eyes along the 6-o'clock sector and in the inferior quadrant (
Table 5).
Table 6 shows the AROC curves for the sectors with significant thinning of the total retina, IRLs, or NFL in the SGPPG eyes versus the healthy eyes, as determined by comparison of the results based on the macular subfields, GSC, and ETDRS chart. In the macular subfield analysis of the mean thickness of the macular layers in the outer sectors (3–6 mm from the foveal center), the AROC curve for total retinal thickness (0.65 ± 0.07) was significantly less than that for IRL thickness (0.78 ± 0.06;
P = 0.004), which was significantly greater than that for NFL thickness (0.65 ± 0.07;
P = 0.018). In the inferior outer hemicircular sector, the AROC curve for IRL thickness was significantly greater than those for total retinal (
P = 0.004) and macular NFL (
P = 0.017) thicknesses. In the individual sectors of the GSC, the AROC curve for the IRL thickness (0.86 ± 0.05) was the greatest in the inferior temporal outer sector, and this value was significantly greater than the AROC curve in the same sector for the total retinal and NFL thickness (
P < 0.001 and
P = 0.001, respectively). Further, the AROC curve for the IRL thickness was significantly greater in the inferior temporal outer sector than in the inferior nasal outer sector (
P = 0.004). On the ETDRS chart, the AROC curve for the IRL thickness was significantly greater in the temporal outer sector than in the nasal outer sector and superior outer sector (
P = 0.003 and
P = 0.047, respectively), but not the inferior outer sector.
As shown in
Table 6, overall, the AROC curve for the IRL thickness in the inferior temporal outer sector (GSC) was significantly greater than for the IRL thicknesses over the whole macula (1–6 mm from the foveal center;
P = 0.005), in the outer ring (3–6 mm from the foveal center;
P = 0.03), in the inferior hemiretinal sector (
P = 0.013), and in the inferior outer hemicircular sector (
P = 0.036) of the macular subfields.
Table 7 shows the AROC curves with significant differences in the mean cpNFL thickness between the healthy eyes and the SGPPG eyes in the 6-o'clock sector (when 12-hour sectors were compared) and the inferior quadrant (when quadrants were compared). The AROC curve for the IRL thickness in the inferior temporal outer sector (GSC) was significantly larger than these sectors (
P = 0.001 and 0.009, respectively).
We calculated the variability of measurements of the total retinal and macular NFL thicknesses (automatic measurements) in 13 healthy eyes and 12 SGPPG eyes according to the macular subfields (two, four, or all sectors;
Table 8), GSC, ETDRS chart, or cpNFL thickness by 24-hour sectors or quadrants. Overall, the measurements tended to be less variable in the healthy eyes (macular subfields: CV of total retina = 0.26%–0.48%, CV of macular NFL = 2.02%–7.00%; GSC: CV of total retina = 0.46%–0.59%, CV of macular NFL = 2.47%–9.40%; ETDRS chart: CV of total retina = 0.57%–0.92%; CV of macular NFL = 2.61%–14.30%; and cpNFL: CV of average cpNFL =1.52%, CV of regional cpNFL = 2.25%–7.26%) than in the SGPPG eyes (macular subfields: CV of total retina = 1.01%–1.98%, CV of macular NFL = 2.88%–9.47%; GSC: CV of total retina = 0.88%–2.24%, CV of macular NFL = 2.84%–16.32%; ETDRS chart: CV of total retina = 0.30%–1.08%, CV of macular NFL = 2.49%–23.07%; and cpNFL: CV of average cpNFL = 1.60%, CV of regional cpNFL = 2.72%–11.19%). Thus, the measurements also tended to be less variable for total retina and cpNFL thicknesses than for macular NFL thickness in both the healthy eyes and the SGPPG eyes. Macular NFL thickness showed relatively high variability in the inner sectors (CV = 5.02%–9.47%) compared with the outer sectors (CV = 2.18%–3.21%) of the macular subfields, in the temporal sectors (CV = 4.59%–16.32%) compared with the nasal sectors (CV = 2.47%–10.06%) on the GSC, and in the temporal sectors (CV = 10.51%–23.07%), compared with the nasal sectors (CV = 3.53%–10.04%) on the ETDRS chart.
Table 9 shows the interobserver agreement for the IRL thickness measurements in various macular sectors. Overall, the IRL thickness measurements showed comparably small variability between the healthy eyes (CV = 0.38%–1.86%) and the SGPPG eyes (CV = 0.34%–1.29%).