Morphology of retinal vessels in the optic disk in a Göttingen minipig experimental glaucoma model

Objective: To compare the morphology of normal, healthy Gottingen minipig retinal vessels of the optic disk with experimentally induced glaucomatous optic disks in order to identify the glaucomatous excavation. Present results were compared to human glaucoma findings.

Procedure: Sixteen eyes from eight Göttingen minipigs were studied using fundoscopic photography and fluorescein angiography. Experimental glaucoma was then induced in the left eyes over 14 months, and changes in the optic disk vessels were assessed using fundoscopic photography and fluorescein angiography. The changes were compared with those previously reported in humans.

Results: Regarding the number of vessels, the location from where they emerge and the sectors of the optic disk that they cross, arterial and retinal vessels in Göttingen minipigs present a more asymmetric layout than in humans. The central excavation is filled by the central venous ring. Changes in the glaucomatous optic disk include arteriolar incurvation, and sometimes, nasal, and peripheral displacement of the arterioles that emerge between the ganglion cell axons of the neuroretinal ring. No angiographic changes were observed in the experimental glaucoma model.

Conclusions: The changes in the glaucomatous optic disk of the minipig imply a predominant involvement of the arterioles. However, in humans with primary open-angle glaucoma (POAG), both the arterioles and the venules are displaced, and the central excavation is easier to distinguish, because of the absence of a central venous ring.