[A new model of induced ocular hyperpressure using the minipig]

To characterize a new animal model of moderate chronic hyperpressure obtained by obstruction of the iridocorneal angle (ICA) in the minipig.

Intraocular hyperpressure was induced in one eye (left) using an injection of methylcellulose (4%) in the anterior chamber of six healthy adult minipigs. Intraocular pressure (IOP) was measured before injection and at D+60 and D+180. The clinical condition thus created was regularly assessed with the following procedures: fundus photography, electroretinography (ERG) to evaluate retinal function, scanning laser ophthalmoscopy (SLO) angiography to measure the arteriovenous filling times (AVFT). Optical microscopy was also performed to evaluate iridocorneal angle and inner retinal layers.

In all instances the injection produced a significant increase in the IOP accompanied by a mydriasis, as well as a significant increase in the AVFT and reduction (abolition in some cases) in the i-wave of the ERG. Fundus examination also revealed a blurred aspect and reduction in the calibre of the retinal blood vessels. Similarly, all experimental eyes showed, at optical microscopy, obstruction of the ICA as well a significant loss of of retinal ganglion cells.

Our results suggest that the above pathophysiological processes, triggered by the induced hyperpressure, share many similarities with human chronic open-angle glaucoma. Consequently, our model, which is very easy to create, could be used to test new therapeutic agents such as neuroprotective drugs.