Lamina cribrosa shape in non-human primates is different from that of humans

Non-human primates (NHPs) are a crucial model for studying glaucoma because of their similarities to humans in anatomy, physiology and pathology. Our goal in this study was to quantify in vivo NHP lamina cribrosa (LC) shapes at low, normal, and elevated intraocular pressures (IOPs), and compare them with literature reported values for in vivo human LCs. We imaged the optic nerve heads (ONH) of seven eyes from six rhesus macaque monkeys using spectral-domain optical coherence tomography (SD-OCT) at several IOP levels while keeping intracranial pressure at baseline. LC shape was characterized by measuring shape index (SI) and curvedness from manually delineated marks of the anterior LC surface. We found that LC shape in NHPs was more similar across individuals at normal IOP than it is in humans. This was, in part, because the NHPs LCs did not exhibit the characteristic horizontal central ridge seen in human LCs and were instead less saddle-shaped and more trough-shaped. With increasing IOP, NHPs LCs curvedness increased, without significant changes in SI, differing from the human response where SI decreases. These findings emphasize the importance of characterizing species-specific differences in anatomy and biomechanics, and the need to determine how these differences may impact susceptibility to glaucomatous damage.