[Morphological and Quantitative Changes in Retinal and Optic Nerve Vessels in Experimental Glaucoma Model with Elevated IOP for 7 Weeks].

Introduction: Glaucoma is characterised by progressive loss of retinal ganglion cells and axons. Experimental research has concentrated on understanding the pathophysiological mechanisms involved in glaucomatous damage. It is still a matter of debate whether neurons or capillaries are primarily damaged by elevated intraocular pressure (IOP). The aim of this study was to detect IOP-induced vascular changes in the vessels of the optic nerve head and the main vessels of the retina in vivo.

Methods: Experimental glaucoma was induced in adult Sprague Dawley rats by cauterisation of three episcleral veins of the left eye (n = 3). In vivo, retinal vessel calibre was measured manually using a peripapillary scan with SD-OCT (Heidelberg Engineering) at baseline and after seven weeks of IOP elevation. The animals were then sacrificed and the optic nerve was fixed with 30% glutaraldehyde and cross-sections stained with paraphenylene diamine to mark the vessels. Contralateral eyes served as controls. Pictures were taken and number of vessels, vessel calibre and area were calculated and compared.

Results: IOP was significantly elevated (p < 0.001). In optic nerve cross sections, the number of capillaries did not differ significantly between animals with elevated IOP and controls. However, vessel calibre and area were significantly reduced (p < 0.001) in glaucomatous optic nerves. The calibre of the retinal vessels was significantly lowered - by 9.22% (p = 0.021).

Conclusion: Retinal arterioles and optic nerve capillaries respond sensitively to abnormal pressure elevation in vivo, showing high and early vulnerability. The vascular responses may influence secondary neuronal responses, which culminate in the death of ganglion cells and blindness, as occurs in clinical glaucoma.