Microstructural Deformations Within the Depth of the Lamina Cribrosa in Response to Acute In Vivo Intraocular Pressure Modulation

Abstract

Purpose The lamina cribrosa (LC) is a leading target for initial glaucomatous damage. We investigated the in vivo microstructural deformation within the LC volume in response to acute IOP modulation while maintaining fixed intracranial pressure (ICP). Methods In vivo optic nerve head (ONH) spectral-domain optical coherence tomography (OCT) scans (Leica, Chicago, IL, USA) were obtained from eight eyes of healthy adult rhesus macaques (7 animals; ages = 7.9–14.4 years) in different IOP settings and fixed ICP (8–12 mm Hg). IOP and ICP were controlled by cannulation of the anterior chamber and the lateral ventricle of the brain, respectively, connected to a gravity-controlled reservoir. ONH images were acquired at baseline IOP, 30 mm Hg (H1-IOP), and 40 to 50 mm Hg (H2-IOP). Scans were registered in 3D, and LC microstructure measurements were obtained from shared regions and depths. Results Only half of the eyes exhibited LC beam-to-pore ratio (BPR) and microstructure deformations. The maximal BPR change location within the LC volume varied between eyes. BPR deformer eyes had a significantly higher baseline connective tissue volume fraction (CTVF) and lower pore aspect ratio ( P = 0.03 and P = 0.04, respectively) compared to BPR non-deformer. In all eyes, the magnitude of BPR changes in the anterior surface was significantly different (either larger or smaller) from the maximal change within the LC (H1-IOP: P = 0.02 and H2-IOP: P = 0.004). Conclusions The LC deforms unevenly throughout its depth in response to IOP modulation at fixed ICP. Therefore, analysis of merely the anterior LC surface microstructure will not fully capture the microstructure deformations within the LC. BPR deformer eyes have higher CTVF than BPR non-deformer eyes.

Under Pressure: Lamina Cribrosa Pore Path Tortuosity in Response to Acute Pressure Modulation

“…The same patterns of response were detected in the same eyes when examining the LC microstructure in the entire LC depth in a previous study by our group. 30 This indicates that, within the pressure range used in this study, the inherent properties of the LC have a stronger impact on the response pattern than does orientation (anteroposterior vs. centripetal) of the inflicting force. We intentionally selected a pressure range that spanned from the clinical range (high IOP and ICP settings) to an exaggerated physiologic level (highest IOP and ICP) in order to capture the full range of tissue responses.…”

“…In a recent publication, we demonstrated that microstructural deformation in response to pressure modulation occurs throughout the lamina volume and is not captured by anterior lamina analysis. 30 In this study, we evaluated the pore path through the entire LC volume.…”

Features Associated with Visible Lamina Cribrosa Pores in Individuals of African Ancestry with Glaucoma: Primary Open-Angle African Ancestry Glaucoma Genetics (POAAGG) Study

“…Additionally, LCPs are visible in 71% of POAG patients compared to 29.3% of controls [ 17 ]. Although several studies have characterized the changes to the LC in patients with glaucoma, few have investigated the associations between LCPs and demographic and ocular characteristics in African-ancestry populations [ 18 , 19 , 20 ]. Existing data show that African-ancestry individuals have a larger total LC area and a greater number of LCPs; however, there is no evidence linking these findings to a higher risk of glaucoma [ 5 , 16 ].…”

Optical coherence tomography angiography features in patients with idiopathic macular holes before and after vitrectomy

“…Optical coherence tomography (OCT) has recently become the primary imaging tool for diagnosing IMH and con rming anatomical success after IMH surgery [10]. It clearly displays the retinal microstructure, making it easier to observe changes in external limiting membrane (ELM), ellipsoid zone (EZ) and cone interdigitation zone (CIZ) postoperatively [11,12]. Nevertheless, traditional OCT can only follow the repair of the macular hole from a two-dimensional perspective, which cannot be quanti ed and re ned, making it hard to study the role of retinal vessels and nerves in macular hole repair [11].…”