Peripapillary border tissue of the choroid and peripapillary scleral flange in human eyes

Purpose To assess dimensions and associations of the peripapillary border tissue of the choroid (PBT-C) and peripapillary scleral flange (PBT-S). Methods The histomorphometric investigation included histological sections of enucleated eyes of Caucasian patients. Using light microscopy, the PBT dimensions were measured. Results The study included 85 eyes (85 patients) with an age of 62.0 years (14.1 years) (mean (SD)) (range:37-87 years) and mean axial length of 26.7 mm (3.5 mm) (range:21.0-37.0 mm). Thicker PBT-C thickness (mean: 68.8 mu m (35.7 mu m)) was associated with shorter axial length (p < 0.001; standardized regression coefficient beta: -0.50), and longer PBT-C length (mean: 531 mu m (802 mu m)) was correlated with longer axial length (p < 0.001;beta:0.66). PBT-C cross-sectional area (mean 17 050 mu m(2) (10 420 mu m(2))) was not significantly associated with axial length (p = 0.37). Decreasing with longer axial length (p < 0.001;beta:0.64), the angle between PBT-C and Bruch's membrane was approximately 90 degrees in non-highly myopic eyes without overhanging Bruch's membrane (BM), it ranged between 100 degrees and 180 degrees in eyes with BM overhanging into the intrapapillary region, and it was close to 0 degrees in eyes with parapapillary gamma zone. Thicker thickness of PBT-S (mean:83 mu m (21 mu m)) was correlated with presence of glaucoma (p = 0.02). Optic nerve pia mater thickness (mean:109 mu m (44 mu m)) increased with glaucoma presence (p = 0.046;beta:0.31) but not with axial length (p = 0.34). Conclusions Peripapillary border tissue of the choroid (PBT-C) and PBT-S as continuation of the optic nerve pia mater are distinct structures, with PBT-C remodelling during myopic axial elongation and PBT-S being mostly independent of axial elongation. PBT-C and PBT-S may be of importance for the optic nerve head biomechanics and PBT-C for separation of the choroidal space from the intrapapillary compartment.