Immediate Changes in Peripapillary Retinal Vasculature after Intraocular Pressure Elevation -an Optical Coherence Tomography Angiography Study

<b>Purpose</b>: To investigate changes in peripapillary retinal vessel density after acute intraocular pressure (IOP) elevation caused by laser peripheral iridotomy (LPI) in primary angle-closure suspects (PACS) by optical coherence tomography angiography (OCTA). <b>Materials and Methods</b>: Ninety-seven participants with PACS were included in this cross-sectional observational study. OCTA and IOP measurement were performed at baseline and 1 h after LPI. PACS eyes were further divided into three groups according to IOP increase 1 h after LPI (group 1 = IOP elevation &lt;5 mmHg, 42eyes; group 2 = IOP elevation ≥5 mmHg and &lt;10 mmHg, 34 eyes; group 3 = IOP elevation ≥10 mmHg, 21eyes). The changes of vessel density in radial peripapillary capillary (RPC) and entire retina were compared among groups. <b>Results</b>: When all eyes were included, the vessel density of RPC and entire retina 1 h after LPI were significantly decreased compared to the baseline (RPC: 64.5 ± 7.9 vs.67.8 ± 6.8, <i>P</i> &lt; .001; retina: 86.3 ± 4.6 vs.88.3 ± 3.8, <i>P</i> &lt; .001). There were significant differences among the three groups in the RPC and retinal vessel density at 1 h after LPI (RPC: 67.4 ± 7.3 vs. 63.2 ± 7.6 vs. 60.9 ± 7.5, <i>P</i> = .003; retinal: 87.7 ± 4.0 vs. 85.8 ± 4.5 vs. 84.3 ± 5.2, <i>P</i> = .015). In group 2 with an increased IOP from 5 mmHg to 10 mmHg, the reduction of vessel density in the RPC was more significant than that of the entire retina (RPC vs. retina: 7.1 ± 10.0% vs. 3.0 ± 4.4%, <i>P</i> = .006). <b>Conclusions</b>: LPI-induced IOP spikes resulted in a decrease in retina vessel density with PACS eyes by OCTA. The reduction of RPC vessel density was more significant than that of the entire retina in the subgroup of IOP increase from 5 to 10 mmHg. This suggests that vessel density in RPC was more sensitive to IOP increase than that of the entire retina in the peripapillary area.<b>研究目的</b>：本研究旨在通过光学相干断层扫描血管成像（optical coherence tomography angiography, OCTA），探究原发性房角关闭疑似者（primary angle-closure suspects, PACS）在接受激光周边虹膜切除术（laser peripheral iridotomy, LPI）后出现急性眼压（intraocular pressure, IOP）升高时，其视盘周围视网膜血管密度的变化情况。<b>材料与方法</b>：本横断面观察性研究共纳入97名原发性房角关闭疑似者受试者。分别在基线状态及激光周边虹膜切除术1小时后，对受试者进行光学相干断层扫描血管成像检查与眼压测量。根据激光周边虹膜切除术1小时后的眼压升高幅度，将纳入的患眼进一步分为三组：第1组（眼压升高幅度<5 mmHg，共42只眼）、第2组（眼压升高幅度≥5 mmHg且<10 mmHg，共34只眼）、第3组（眼压升高幅度≥10 mmHg，共21只眼）。比较三组患眼的视盘周围放射状毛细血管（radial peripapillary capillary, RPC）及全视网膜血管密度的变化情况。<b>结果</b>：纳入所有患眼分析时，激光周边虹膜切除术1小时后的视盘周围放射状毛细血管与全视网膜血管密度均较基线显著降低（视盘周围放射状毛细血管：64.5±7.9 vs 67.8±6.8，*P*<.001；全视网膜：86.3±4.6 vs 88.3±3.8，*P*<.001）。三组患眼在激光周边虹膜切除术1小时后的视盘周围放射状毛细血管及视网膜血管密度均存在显著组间差异（视盘周围放射状毛细血管：67.4±7.3 vs 63.2±7.6 vs 60.9±7.5，*P*=.003；全视网膜：87.7±4.0 vs 85.8±4.5 vs 84.3±5.2，*P*=.015）。在眼压升高幅度为5~10 mmHg的第2组中，视盘周围放射状毛细血管的血管密度降低幅度显著高于全视网膜（视盘周围放射状毛细血管 vs 全视网膜：7.1±10.0% vs 3.0±4.4%，*P*=.006）。<b>结论</b>：激光周边虹膜切除术诱发的眼压升高可导致原发性房角关闭疑似者患眼的视网膜血管密度降低，该变化可通过光学相干断层扫描血管成像观测到。在眼压升高幅度为5~10 mmHg的亚组中，视盘周围放射状毛细血管的血管密度降低幅度显著高于全视网膜。这表明视盘周围区域内，视盘周围放射状毛细血管的血管密度对眼压升高的敏感性高于全视网膜血管密度。