Quantitative Association Between Peripapillary Bruch's Membrane Shape and Intracranial Pressure

PURPOSE. The purpose of this study was to determine if there is a quantitative relationship between chronic intracranial pressure (ICP) and peripapillary Bruch's membrane (pp-BM) shape and to determine whether change in pp-BM shape can be detected within 1 hour after ICP lowering by lumbar puncture (LP). METHODS. In this study, 30 degrees nasal-temporal optical coherence tomography B-scans were obtained within 1 hour before and after LP in 39 eyes from 20 patients (age = 23-86 years, 75% female, ICP [opening pressure] = 10-55 cm H2O). A total of 16 semi-landmarks defined pp-BM on each image. Geometric morphometric analysis identified principal components of shape in the image set. Generalized estimating equation models, accounting for within-subject correlation, were used to identify principal components that were associated with chronic ICP (comparing pre-LP images between eyes) and/or acute ICP changes (comparing pre-and post-LP images within eyes). The pp-BM width and anterior pp-BM location were calculated directly from each image and were studied in the same manner. RESULTS. Principal component 1 scalar variable on pre-LP images was associated with ICP (P < 0.0005). Principal component 4 magnitude changed within eyes after LP (P = 0.003). For both principal components 1 and 4, lower ICP corresponded with a more posterior position of pp-BM. Chronic ICP was associated with both pp-BM width (6.81 mu m/cm H2O; P = 0.002) and more anterior location of temporal and nasal pp-BM margins (3.41, 3.49 mu m/cm H2O; P < 0.0005, 0.002). CONCLUSIONS. This study demonstrates a quantitative association between pp-BM shape and chronic ICP level. Changes in pp-BM shape are detectable within 1 hour of lowering ICP. ppBM shape may be a useful marker for chronic ICP level and acute ICP changes. Further study is needed to determine how pp-BM shape changes relate to clinical markers of papilledema.