Anterior Segment Anatomy and Conventional Outflow Physiology of the Tree Shrew (Tupaia belangeri)

Jessica V. Jasien, A. Thomas Read, Joseph Van Batenburg-Sherwood, Kristin M. Perkumas, C. Ross Ethier, W. Daniel Stamer, Brian C. Samuels

Research output: Contribution to journalArticlepeer-review


PURPOSE. Rodent and primate models are commonly used in glaucoma research; however, both have their limitations. The tree shrew (Tupaia belangeri) is an emerging animal model for glaucoma research owing in part to having a human-like optic nerve head anatomy, specifically a collagenous load-bearing lamina. However, the anterior segment anatomy and function have not been extensively studied in the tree shrew. Thus, the purpose of this study was to provide the first detailed examination of the anterior segment anatomy and aqueous outflow facility in the tree shrew. METHODS. Aqueous outflow dynamics were measured in five ostensibly normal eyes from three tree shrews using the iPerfusion system over a range of pressures. Gross histological assessment and immunohistochemistry were performed to characterize anterior segment anatomy and to localize several key molecules related to aqueous outflow. RESULTS. Anterior segment anatomy in tree shrews is similar to humans, demonstrating a scleral spur, a multilayered trabecular meshwork and a circular Schlemm's canal with a single lumen. Average outflow facility was 0.193 μL/min/mm Hg (95% confidence interval, 0.153-0.244), and was stable over time. Outflow facility was more similar between contralateral eyes (approximately 5% average difference) than between eyes of different animals. No significant dependence of outflow facility on time or pressure was detected (pressure-flow nonlinearity parameter of 0.01 (95% % confidence interval, -0.29 to 0.31 CI μL/min/mm Hg). CONCLUSIONS. These studies lend support to the usefulness of the tree shrew as a novel animal model in anterior segment glaucoma and pharmacology research. The tree shrew's cost, load-bearing collagenous lamina cribrosa, and lack of washout or anterior chamber deepening provides a distinct experimental and anatomic advantage over the current rodent and nonhuman primate models used for translational research.

Original languageEnglish (US)
Article number21
JournalInvestigative Ophthalmology and Visual Science
Issue number1
StatePublished - Jan 2022
Externally publishedYes


  • Anterior segment
  • Aqueous humor facility
  • Aqueous outflow
  • Histology
  • Tree Shrew

ASJC Scopus subject areas

  • Ophthalmology
  • Sensory Systems
  • Cellular and Molecular Neuroscience


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