Animal models provide an important platform for laboratory investigation of cellular processes underlying glaucoma pathogenesis, as well as to evaluate potential therapeutic interventions. Several inducible models have been developed to produce sustained intraocular pressure (IOP) elevation, the most important risk factor for glaucoma. Methods that have been applied to elevate IOP include: hypertonic saline injection in episcleral veins1, laser photocoagulation of the trabecular meshwork2 or of the limbal veins3, and intracameral injection of substances such as ghost red blood cells4, microbeads5,6 and viscoelastic agents7. Each approach has its advantages and limitations.

A good model for glaucoma should mimic the disease process, with minimal complication such as trauma, inflammation and media opacities. These complications are frequently associated with the procedures used to induce IOP elevation, and can confound interpretation of outcomes. For example, paracentesis of the anterior chamber, even when foreign substances are not introduced, has been shown to cause trauma and inflammation that is not representative of typical glaucomatous change8,9. In addition to the importance of avoiding inflammation, maintaining optical clarity facilitates in vivo imaging and electrophysiology to monitor disease progression. Although it is unclear to what extent these complications may affect disease investigations, it may be better to avoid penetrating the eye during model induction. The circumlimbal suture approach avoids penetration of the globe and facilitates in vivo longitudinal assessment of retinal structure and function. More importantly, this model differs from previous ones in its capacity to return IOP to baseline values by removal of the suture when required. IOP normalization may be useful for studying the cellular and molecular correlates of reversible and irreversible ganglion cell injury10,11,12,13,14.

This article focuses on the technique for model induction. Characterization of retinal injuryinduced by this model in rats and mice can be found in greater detail elsewhere15,16,17,18,19.