Long-term Remodeling Response in the Lamina Cribrosa Years after Intraocular Pressure Lowering by Suturelysis after Trabeculectomy

Abstract

To measure the remodeling of the lamina cribrosa (LC) years after IOP lowering by suturelysis. Cohort study. Glaucoma patients were imaged 20 minutes after laser suturelysis following trabeculectomy surgery and at their follow-up appointment 1-4 years later (16 image pairs; 15 persons). Non-invasive optical coherence tomography (OCT) imaging of the eye. Deformation calculated by correlating OCT scans of the LC immediately after IOP lowering by suturelysis and those acquired years later (defined as remodeling strain). The LC anterior border moved 60.9 ± 54.6 μm into the eye (p=0.0006), and the LC exhibited regions of large local stretch in the anterior-posterior direction on long-term, maintained IOP lowering, resulting in a mean anterior-posterior remodeling strain of 14.0 ± 21.3% (p=0.03). This strain and the LC border movement was 14 times and 124 times larger, respectively, than the direct response to IOP lowering by suturelysis. A larger anterior LC border movement was associated with greater mean anterior-posterior remodeling strain (p=0.004). A thinner retinal nerve fiber layer (RNFL) at suturelysis was also associated with greater mean anterior-posterior remodeling strain at follow-up (p=0.04). Worsening visual field indexes during follow-up were associated with a greater mean circumferential remodeling strain (p=0.02), due to regions of large local circumferential stretch of the LC. Eyes with a more compliant LC torsional shear strain response at lysis was associated with worse mean deviation at follow-up (p=0.03) CONCLUSION: Strains and LC border position changes measured years after IOP lowering are far larger than the immediate response to IOP lowering, and indicate dramatic remodeling of the LC anatomical structure caused by IOP lowering and glaucoma progression. The remodeling strains indicate substantial local stretch in the anterior-posterior direction and is associated with movement of the LC anterior border into the eye. Eyes with greater direct strain response to IOP-lowering, greater glaucoma damage at suturelysis, and greater worsening of visual field at follow-up experienced greater remodeling.