Long-Term Remodeling Response in the Lamina Cribrosa Years after IOP Lowering by Suturelysis after Trabeculectomy

Abstract

Objective: To measure the active remodeling of the lamina cribrosa (LC) years after IOP lowering by suturelysis. Design: Cohort study. Participants: 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). Intervention: Non-invasive optical coherence tomography (OCT) imaging of the eye. Main Outcomes: Deformation calculated by correlating OCT scans of the LC immediately after IOP lowering by suturelysis and those acquired years later (defined as follow-up strain). Results: Mean LC follow-up strain in the anteroposterior direction (Ezz) was 14.0 ± 21.3% (mean, standard deviation, p=0.03), while the LC anterior border moved 60.9 ± 54.6 μm into the eye (p=0.0006) on long-term, maintained IOP lowering. Ezz at follow-up was 14 times larger than the direct Ezz response to IOP lowering by suturelysis. There was a significant association between larger LC anterior movement and greater Ezz (p=0.004) at follow-up. Thinner retinal nerve fiber layer (RNFL) at suturelysis was associated with greater follow-up Ezz (p=0.04). Worsening visual field indexes during follow-up were associated with greater LC widening (positive remodeling Eθθ, p=0.02). Eyes with a greater counterclockwise twist (positive Eθz) at suturelysis had greater reversal clockwise twist at follow-up (negative remodeling Eθz, p=0.007). Conclusion: Follow-up strains and LC border position changes measured years after IOP lowering are far larger than the immediate strain response and LC border movement response to IOP lowering and indicate dramatic remodeling of the LC anatomical structure caused by IOP lowering and glaucoma progression. The remodeling includes a substantial increase in LC thickness and movement into the eye. Eyes with greater direct strain response to IOP-lowering strains, greater glaucoma damage at suturelysis, and greater worsening of visual field at follow-up experienced greater remodeling.