Ha et al. investigated the relationship between the posterior bowing of the lamina cribosa – in subjects with early POAG medically treated – and the subsequent risk and rate of visual field progression. They used swept-source OCT to investigate the optic nerve head anatomy, and the main parameters used to perform the statistical analysis were derived from the geometric distance between the anterior laminar insertion and the mean position of the anterior laminar surface (called lamina cribosa curvature index, LCCI). Assessment of the visual field progression was performed using a linear regression of the MD against time.
One hundred and one eyes were analyzed. It should be mentioned that about 20% of the OCT scans were not analyzed because of poor image quality. The baseline MD was –3.8 ± 3.4 dB and the mean rate of progression –0.18 ± 0.33 dB/year over a 3.6 ± 0.8-years period.
Among all the demographic, clinical and anatomical parameters included in the univariate and multivariate analysis, only the mean adjusted LCCI was significantly associated to a higher rate of visual field progression. It should be noted that the mean IOP, IOP fluctuations, and baseline MD were not significantly associated to the rate of visual field progression.
I think that this study performed in a large cohort of subjects and using careful evaluations of the lamina cribosa anatomy adds some evidences of the potential role of the lamina cribosa biomechanics in the glaucoma pathophysiology. It particularly emphasizes the importance of the lamina cribosa curvature and posterior bowing.
This study emphasizes the importance of the lamina cribosa curvature and posterior bowingSurprisingly, the untreated and treated IOP were not associated to the rate of visual field progression. It should be noted that the study was conducted in Asia, and most of the subjects likely had normal-tension glaucoma (the authors mentioned that the mean pretreatment IOP was 16.2 ± 4.3 mmHg in the discussion). Of course, it will be interesting to duplicate such analysis in other ethnicities and also subjects with high tension glaucoma. It is possible that the respective role of the IOP level and lamina cribosa curvature would have been different.