Impact of ab-interno trabeculectomy on Bruch's membrane opening-based morphometry of the optic nerve head for glaucoma progression analysis.

Purpose: To analyze the longitudinal change in Bruch's membrane opening minimal rim width (BMO-MRW) and circumpapillary retinal nerve fiber layer (RNFL) thickness using spectral domain optical coherence tomography (SD-OCT) after glaucoma surgery via ab-interno trabeculectomy in adult glaucoma patients.

Methods: Retrospective audit of 65 eyes of 65 participants undergoing ab-interno trabeculectomy using electroablation of the trabecular meshwork. In 53 eyes, surgery was combined with phacoemulsification and posterior chamber lens implantation. Pre- and postoperative SD-OCT examinations of the optic nerve head (ONH), intraocular pressure (IOP), and visual field data were analyzed. Longitudinal change in morphometric SD-OCT parameters of the ONH was compared and correlated to change in IOP and visual field function.

Results: BMO-MRW increased significantly between baseline (BL) and follow-up (FU) within the first 6 months after surgery (BL = 167.85 ± 90 μm; FU = 175.59 ± 89 μm; p = 0.034). This increase correlated with postoperative lowering of IOP (rho = - 0.41; p = 0.016). Nine months after surgery (range, 7-12 months), there was no significant change in BMO-MRW (BL = 196.79 ± 79; FU = 196.47 ± 85 μm; p = 0.95), while in later follow-up, a decrease of BMO-MRW was found (BL = 175.18 ± 78; FU = 168.65 ± 72; p = 0.05). RNFL thickness was unchanged in early (p > 0.16) and significantly decreased in later follow-up (p = 0.009). Mean deviation (MD) of visual field function did not show a significant change before and after surgery.

Conclusion: Electroablative ab-interno trabeculectomy leads to a significant transient mild increase in BMO-MRW. This increase was shown to correlate with IOP lowering. Significant loss of BMO-MRW in later follow-up may reflect insufficient IOP reduction by surgery. The parameters RNFL thickness and MD seem less impacted directly by surgery.