Three-dimensional reconstruction of normal and early glaucoma monkey optic nerve head connective tissues

Purpose. To introduce high-resolution, digital three-dimensional (3-D) reconstruction of the connective tissues of the optic nerve head (ONH). Methods. Trephinated ONH and peripapillary sclera from both eyes of three monkeys with early glaucoma (EG; one eye normal, one eye given laser-induced EG) were embedded in paraffin and serial sectioned at 3-mum thickness from the vitreous surface through the orbital optic nerve, with the embedded tissue block face stained and imaged after each cut. Each image was aligned, and then the scleral canal wall, sclera, border tissue of Elschnig, Bruch's membrane, lamina cribrosa, optic nerve septa, pial sheath, and vasculature were delineated as unique objects. Delineated images were stacked, color mapped, and volume rendered and then serial sagittal and transverse digital sections of the resultant voxel geometries were viewed and measured. Results. Substantial differences in the 3-D architecture of the peripapillary sclera, scleral canal wall, and lamina cribrosa were present among the three normal eyes. All three EG eyes displayed permanent posterior deformation of the central lamina cribrosa, as well as expansion of the anterior and posterior neural canal openings in comparison with their respective contralateral normal control eyes. Peripherally, whereas laminar deformation was greatest inferiorly or superiorly in all three EG eyes, statistically significant deformation was present in all four quadrants of all three eyes. Conclusions. High-resolution, digital 3-D reconstructions of the load-bearing connective tissues of the monkey ONH confirm that the ONH connective tissues are profoundly altered at the onset of detectable ONH surface change in experimental glaucoma.