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Abstract #9691 Published in IGR 5-3
Anterior scleral canal geometry in pressurised (IOP 10) and non-pressurised (IOP 0) normal monkey eyes
Bellezza AJ; Rintalan CJ; Thompson HW; Downs JC; Hart RT; Burgoyne CFBritish Journal of Ophthalmology 2003; 87: 1284-1290
AIMS: To characterize lamina cribrosa and anterior scleral canal wall architecture in pressurized (IOP 10 mmHg) and non-pressurised (IOP 0 mmHg) normal monkey eyes. METHODS: Eight normal eyes from eight monkeys were enucleated before sacrifice and the optic nerve heads (ONH) trephined and immersion fixed in glutaraldehyde (IOP 0). Nine normal eyes from nine monkeys were perfusion fixed in situ with paraformaldehyde at IOP 10 mmHg (IOP 10), and the ONHs trephined and stored in glutaraldehyde. Each ONH specimen was embedded in glycol methacrylate and cut into vertical or horizontal, 4 μm thick, serial sections. Within digitized images of every sixth section, anterior laminar position and laminar thickness were measured at nine evenly spaced locations across the scleral canal opening. Additionally, scleral canal diameters at Bruch's membrane (SCD-B) and at the anterior laminar insertion (SCD-ALI) were measured within the 15 middle section images of each vertically sectioned ONH. RESULTS: Anterior laminar position was significantly more anterior (nearer Bruch's membrane) in the IOP 10 eyes, compared with the IOP 0 eyes (116 (± 95% CI; 2) μm versus 184 (2) μm, respectively). Also in the IOP 10 eyes, the lamina cribrosa was thinner (195 (2) μm versus 264 (2) μm) and the scleral canal diameter was larger (SCD-B: 1751 (23) μm versus 1591 (19) μm; SCD-ALI: 1961 (21) μm versus 1717 (17) μm), compared with the IOP 0 eyes. CONCLUSIONS: The anterior scleral canal wall is expanded and the lamina cribrosa is thinned and more tautly stretched within pressurised (perfusion fixed at IOP 10) young monkey eyes, compared with non-pressurized (immersion fixed at IOP 0) young monkey eyes. The constricted scleral canal and the relaxed and thickened lamina in the non-pressurized eyes may represent phenomena that contribute to optic disc swelling in hypotonous eyes.
Dr. A.J. Bellezza, LSU Eye Center, Louisiana State University Health Sciences Center, 2020 Gravier Street, New Orleans, LA 70112, USA
Classification:
2.14 Optic disc (Part of: 2 Anatomical structures in glaucoma)
5 Experimental glaucoma; animal models