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Joshua William Evans, Marla Davis, Sachin Kedar, Deepta Ghate, Peter Timoney, Richard Kielar, Bruce Maley, William O'Connor; Ultramicroscopic study of the Optic Nerve Sheath in Patients with Severe Vision Loss from Idiopathic Intracranial Hypertension- Methodology. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):2237.
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© ARVO (1962-2015); The Authors (2016-present)
Very little is known about the anatomy and pathology of the optic nerve sheath (ONS) in normal and diseased states. The objective of our study is to explore microscopic changes in the ONS in patients with severe and/or progressive vision loss from IIH.
ONS specimens were obtained from patients with IIH after ONS fenestration (cases) and painful blind eye after enucleation (controls). Both procedures were performed by a single surgeon. A 2 x 1 mm ONS window was obtained, divided into 2 parts, fixed and stained per following protocol.Light Microscopy (LM): All specimens were formalin fixed, stained using Hematoxylin-Eosin and examined at 10x and 40x magnification.Transmission electron microscopy (TEM): All specimens were immediately fixed (in Operating room) using 4% paraformaldehyde and 3.5% glutaraldehyde on ice; washed in Cacodylate buffer; postfixed using Osmium tetroxide/buffer mixture; dehydrated through graded concentrations of ethanol washes; and resin embedded. Ultrathin sections were obtained, stained and examined in Philips Tecnai Biotwin 12 TEM at 2900X magnification.Polarization microscopy (PM): All specimens were stained using Picrosirius red and examined under polarization microscope using previously published methods. (Junqueira et al., 1979) Masked experts in LM, TEM and PM performed evaluations for specimen quality (desiccation, trauma and staining) and tissue anatomy (cellularity and collagen arrangement).
Of 13 subjects and 16 eyes enrolled, 7 specimens (6 cases and 1 control) met inclusion and quality control criteria for analysis. Tissue was not obtained in 4 eyes at surgery. 2 specimens were excluded due to alternative diagnosis (meningioma, panophthalmitis). 3 specimens were excluded due to tissue desiccation resulting from increased time interval from resection to tissue fixation.
Adequate quantity and quality ONS specimens were obtained in patients undergoing ONS fenestration and enucleation. Since ONS is susceptible to desiccation, tissue should be fixed immediately in the operating room.
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