A multi-scale/multi-physics model for the theoretical study of the vascular configuration of retinal capillary plexuses based on OCTA data.

The retinal tissue is highly metabolically active and is responsible for translating the visual stimuli into electrical signals to be delivered to the brain. A complex vascular structure ensures an adequate supply of blood and oxygen, which is essential for the function and survival of the retinal tissue. To date, a complete understanding of the configuration of the retinal vascular structures is still lacking. Optical coherence tomography angiography has made available a huge amount of imaging data regarding the main retinal capillary plexuses, namely the superficial capillary plexuses (SCP), intermediate capillary plexuses (ICP) and deep capillary plexuses (DCP). However, the interpretation of these data is still controversial. In particular, the question of whether the three capillary plexuses are connected in series or in parallel remains a matter of debate. In this work, we address this question by utilizing a multi-scale/multi-physics mathematical model to quantify the impact of the two hypothesized vascular configurations on retinal hemodynamics and oxygenation. The response to central retinal vein occlusion (CRVO) and intraocular pressure (IOP) elevation is also simulated depending on whether the capillary plexuses are connected in series or in parallel. The simulation results show the following: (i) in the in series configuration, the plexuses exhibit a differential response, with DCP and ICP experiencing larger pressure drops than SCP; and (ii) in the in parallel configuration, the blood flow redistributes uniformly in the three plexuses. The different vascular configurations show different responses also in terms of oxygen profiles: (i) in the in series configuration, the outer nuclear layer, outer plexiform layer and inner nuclear layer (INL) are those most affected by CRVO and IOP elevation; and (ii) in the in parallel configuration the INL and ganglion cell layer are those most affected. The in series results are consistent with studies on paracentral acute middle maculopathy, secondary to CRVO and with studies on IOP elevation, in which DCP and ICP and the retinal tissues surrounding them are those most affected by ischemia. These findings seem to suggest that the in series configuration better describes the physiology of the vascular retinal capillary network in health and disease.

视网膜组织代谢活性极高，负责将视觉刺激转化为电信号并传递给大脑。复杂的血管结构确保血液和氧气的充足供应，这对视网膜组织的功能和存活至关重要。到目前为止，对视网膜血管结构的形态仍缺乏完整的了解。光学相干断层扫描血管造影技术提供了大量关于主要视网膜毛细血管丛的成像数据，即浅层毛细血管丛（SCP）、中层毛细血管丛（ICP）和深层毛细血管丛（DCP）。然而，对这些数据的解读仍存在争议。特别是，这三个毛细血管丛是串联还是并联的问题仍然是一个争论点。在这项工作中，我们通过利用一个多尺度/多物理场的数学模型来解决这个问题，以量化两种假设的血管结构对视网膜血流动力学和氧合作用的影响。还根据毛细血管丛是串联还是并联模拟了对视网膜中央静脉阻塞（CRVO）和眼内压（IOP）升高的反应。模拟结果显示如下：（i）在串联结构中，各丛表现出不同的反应，DCP和ICP比SCP经历更大的压降；（ii）在并联结构中，血流在三个丛中均匀重新分布。不同的血管结构在氧分布方面也显示出不同的反应：（i）在串联结构中，外核层、外丛状层和内核层（INL）受CRVO和IOP升高的影响最大；（ii）在并联结构中，INL和神经节细胞层受影响最大。串联结果与继发于CRVO的旁中心急性中层黄斑病变的研究以及IOP升高的研究一致，在这些研究中，DCP和ICP以及它们周围的视网膜组织受缺血影响最大。这些发现似乎表明串联结构更好地描述了健康和疾病状态下视网膜毛细血管血管网络的生理情况。