Tridimensional studies on the adult rat optic nerve head

Abstract

SummaryPurposeTo reconstruct rat optic nerve heads (ONHs) with unilateral experimental glaucoma (EG), so as to 3D characterize the normal and early EG ONH anatomy in the rat.MethodsHypertonic saline was unilaterally injected into the episcleral veins of 8 Brown rats that were sacrificed 4 weeks later. Orbital optic nerve (ON) sections were graded. ONH's were 3D reconstructed, delineated, and parameterized. Overall and individual EG versus control eye differences were studied by linear mixed effect models adjusted for multiple comparisons.ResultsThe rat ONH has 2 scleral openings (superior neurovascular and inferior arterial) separated by a sling. In the superior one, the nerve abuts a prominent extension of Bruch's Membrane (BM) superiorly and is surrounded by a plexus. ON and anterior scleral canal opening (ASCO) expansions were significant overall and in 7 EG eyes. In at least 5 EG eyes, significant expansions in BM Opening (BMO) (3–10%), ASCO and Posterior Scleral Canal Openings (PSCO) (8–21 and 8–41%, respectively) were found. ON expansion was correlated to ON damage.ConclusionsThe 3D complexity of the rat ONH has been undervalued in previous 2D studies. ON, BMO and neurovascular canal expand early in response to IOP elevation.