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Elizabeth Cone Kimball, Thao D Nguyen, Mary Ellen Pease, Dan Midgett, Harry Quigley; Confocal Microscopic Analysis of Lamina Cribrosa Displacement in Porcine and Human Eyes. Invest. Ophthalmol. Vis. Sci. 2014;55(13):4251.
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© ARVO (1962-2015); The Authors (2016-present)
To image the lamina cribrosa (LC) and estimate deformation produced by change in intraocular pressure (IOP) in porcine and human eyes in vitro, measuring differences between control and glaucoma tissue.
Ex-vivo porcine eyes (N=3) and normal (N=2) and glaucoma (N=3) human eyes had removal of the optic nerve flush with the peripapillary sclera. A fixture containing PBS stabilized the eye, LC up with a 23G cannula inserted through the cornea, connected to a saline-filled reservoir to control IOP. Using a Zeiss LSM 710 multi-photon microscope (Chameleon Ultra II laser set to 780nm),the LC was imaged at 20x and IOP was set to 5, 15, 30 and 45 mmHg in human and 5, 10, 15, 20, 25 and 30mmHg for porcine. Displacement was measured at a fixed LC beam location at each new IOP level for 15 minutes; every 30 seconds for the first two minutes and 2 minutes thereafter. 2D and 3D (Z-stack) images as 6x6 tiles were collected from the entire LC and peripapillary sclera for future biomechanical analysis. The glaucoma eyes studied contained limited and mild damage according to visual acuity history.
In pilot studies, the glaucoma eyes underwent variable displacement compared to controls, with one greater and one less than normal. On average, 85% of the displacement in control human eyes, 81% in glaucoma, and 86% in porcine eyes, occurred in the first minute, after IOP was changed to a new level (Figure 1), with much slower continued displacement (creep) during the hold period after 1 minute (1-3% change/minutes). Equilibrium levels of displacement were reached more quickly in pig and human glaucoma eyes (12 minutes), than in human control eyes (14 minutes). The porcine lamina (Figure 2A) contained larger and few pores in the LC than the human control (Figure 2B) and glaucoma (Figure 2C) LC. Porcine lamina displaced more than human controls, 5:1 ratio after pressure was raised to 15mmHg and 5:3 after 30mmHg. Human glaucoma eyes displaced more than human controls, 2:1 ratio when pressure was raised to 15mmHg and to 45mmHg.
LC imaging and displacement analysis at high resolution was implemented by confocal microscopy to measure displacement with IOP change. The system utilized will be implemented to obtain detailed lamina/sclera biomechanical analysis.
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