One hundred sixty-two POAG eyes with DH, representing 162 patients, were initially included in the study. Of these, 34 patients were excluded: (1) 19 patients lacked data such as the SD-OCT or AL, (2) nine patients had a poor quality SDP or RNFLP, and (3) eight patients could not match the retinal vessel on the RNFL deviation map and RNFLP. The remaining 128 eyes of 128 patients were examined further in the ensuing analysis.
The study population's clinical characteristics are listed in
Table 1. The mean age on first visit was 59.2 ± 10.8 years. The mean follow-up was 6.0 ± 2.9 years at intervals of 4.5 ± 3.3 months; DH was detected 1.5 ± 0.7 times over the course of 3.4 ± 2.9 months. The most common proximal location of DH was the disc rim (52/128), and the largest number of DHs were detected in the inferotemporal inferior sector (74.3/128). The overall angular extent of DH was 12.02 ± 7.13°, and the overall DH area and DH area/disc area ratio were 0.072 ± 0.04 mm
2 and 0.038 ± 0.026, respectively.
Univariate and stepwise multivariate linear regression analyses were carried out to determine which variables were associated with corrected DH area. A larger corrected DH area was associated with older age (
P < 0.01, standardized
β = 0.29), use of acetylsalicylic acid (ASA;
P = 0.03, standardized
β = 0.18), lower baseline IOP (
P = 0.01, standardized
β = −0.19), and lower cup-to-disc ratio at time of DH detection (
P < 0.01, standardized
β = −0.31) (
Table 2). When the effect of IOP on corrected DH area was separately analyzed, DH area was found to be negatively correlated with the baseline IOP (
R = −0.20,
P = 0.04) (
Fig. 2).
For further evaluation, 88 eyes of 88 patients were assigned to the NTG group (baseline IOP ≤ 21 mm Hg) and 40 eyes of 40 patients to the HTG group (baseline IOP ≥ 22 mm Hg). As comparing clinical characteristics between the two groups, they did not differ in systemic parameters including age (P = 0.52), sex (P = 0.06), diabetes mellitus (P = 0.78), systemic hypertension (P = 0.29), or use of ASA (P = 0.70). On average, the NTG group had 5.9 ± 3.1 years of follow-up at intervals of 4.3 ± 3.1 months; DH was detected 1.5 ± 0.8 times/eye, and lasted for 3.8 ± 3.1 months. The HTG group had 6.1 ± 2.9 years of follow-up at intervals of 4.8 ± 2.3 months; DH was detected 1.4 ± 0.7 times/eye, and lasted for 3.0 ± 2.6 months. There were no significant differences between the two groups in the total follow-up periods (P = 0.42), follow-up intervals (P = 0.68), SDP- and RNFLP-intervals (P = 0.60), number of DH detections (P = 0.49), or duration of DH (P = 0.18). In the baseline phase, there was neither any significant difference in the ocular parameters, including best-corrected visual acuity (P = 0.27), mean deviation of HVF (P = 0.47), pattern standard deviation (PSD) of HVF (P = 0.58), spherical equivalent (P = 0.39), central corneal thickness (P = 0.23), and corrected optic disc area (P = 0.57).
The proximal location, octant location, and angular extent of DH did not show significant differences between the two groups (
P = 0.32, 0.45, and 0.20, respectively) (
Table 3). However, the NTG group had a significantly larger corrected DH area (0.078 ± 0.050 mm
2 vs. 0.060 ± 0.036 mm
2,
P = 0.04) and a larger corrected LMRE of DH (1.162 ± 0.324 mm vs. 0.972 ± 0.251 mm,
P = 0.03). Overall, the DH area/disc area ratio was also larger in the NTG group (0.041 ± 0.028 vs. 0.032 ± 0.022,
P = 0.07) (
Table 4).
On the DH diagrams, the majority of first-detected DHs were located in the inferotemporal inferior sector and started from the mid disc rim. The NTG group showed a more widespread distribution of DHs, which is to say, a distribution farther from the optic disc center, than did the HTG group (
Fig. 3).