title: Trabecular Meshwork Response to Pressure Elevation in the Living Human Eye.
abstract: The mechanical characteristics of the trabecular meshwork (TM) are linked to outflow resistance and intraocular pressure (IOP) regulation. The rationale behind this technique is the direct observation of the mechanical response of the TM to acute IOP elevation. Prior to scanning, IOP is measured at baseline and during IOP elevation. The limbus is scanned by spectral-domain optical coherence tomography at baseline and during IOP elevation (ophthalmodynamometer (ODM) applied at 30 g force). Scans are processed to enhance visualization of the aqueous humor outflow pathway using ImageJ. Vascular landmarks are used to identify corresponding locations in baseline and IOP elevation scan volumes. Schlemm canal (SC) cross-sectional area (SC-CSA) and SC length from anterior to posterior along its long axis are measured manually at 10 locations within a 1 mm segment of SC. Mean inner to outer wall distance (short axis length) is calculated as the area of SC divided by its long axis length. To examine the contribution of adjacent tissues to the effect IOP elevations, measurements are repeated without and with smooth muscle relaxation with instillation of tropicamide. TM migration into SC is resisted by TM stiffness, but is enhanced by the support of its attachment to adjacent smooth muscle within the ciliary body. This technique is the first to measure the living human TM response to pressure elevation in situ under physiological conditions within the human eye.
authors.affiliation: Department of Ophthalmology, UPMC Eye Center, Eye and Ear Institute, Ophthalmology and Visual Science Research Center, University of Pittsburgh School of Medicine; Department of Bioengineering, Swanson School of Engineering, University of Pittsburgh; lkagemann@yahoo.com.
authors.forename: Larry
authors.initials: L
authors.lastname: Kagemann
authors.affiliation: Department of Bioengineering, Swanson School of Engineering, University of Pittsburgh.
authors.forename: Bo
authors.initials: B
authors.lastname: Wang
authors.affiliation: Department of Ophthalmology, UPMC Eye Center, Eye and Ear Institute, Ophthalmology and Visual Science Research Center, University of Pittsburgh School of Medicine.
authors.forename: Gadi
authors.initials: G
authors.lastname: Wollstein
authors.affiliation: Department of Ophthalmology, UPMC Eye Center, Eye and Ear Institute, Ophthalmology and Visual Science Research Center, University of Pittsburgh School of Medicine; Department of Bioengineering, Swanson School of Engineering, University of Pittsburgh.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Ishikawa
authors.affiliation: Department of Ophthalmology, UPMC Eye Center, Eye and Ear Institute, Ophthalmology and Visual Science Research Center, University of Pittsburgh School of Medicine.
authors.forename: Brandon
authors.initials: B
authors.lastname: Mentley
authors.affiliation: Department of Ophthalmology, UPMC Eye Center, Eye and Ear Institute, Ophthalmology and Visual Science Research Center, University of Pittsburgh School of Medicine; Department of Bioengineering, Swanson School of Engineering, University of Pittsburgh; The McGowan Institute for Regenerative Medicine, University of Pittsburgh School of Medicine.
authors.forename: Ian
authors.initials: I
authors.lastname: Sigal
authors.affiliation: Department of Ophthalmology, UPMC Eye Center, Eye and Ear Institute, Ophthalmology and Visual Science Research Center, University of Pittsburgh School of Medicine; Deptartment of Biostatistics, Graduate School of Public Health, University of Pittsburgh.
authors.forename: Richard A
authors.initials: RA
authors.lastname: Bilonick
authors.affiliation: Department of Ophthalmology, UPMC Eye Center, Eye and Ear Institute, Ophthalmology and Visual Science Research Center, University of Pittsburgh School of Medicine; Department of Bioengineering, Swanson School of Engineering, University of Pittsburgh; The McGowan Institute for Regenerative Medicine, University of Pittsburgh School of Medicine.
authors.forename: Joel S
authors.initials: JS
authors.lastname: Schuman
mesh_terms: D006801:Humans; D007429:Intraocular Pressure / Q000502:physiology*; D009884:Ophthalmodynamometry / Q000379:methods*; D041623:Tomography, Optical Coherence / Q000379:methods; D014129:Trabecular Meshwork / Q000502:physiology*