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J. Crawford Downs, Michael E. Ensor, Anthony J. Bellezza, Hilary W. Thompson, Richard T. Hart, Claude F. Burgoyne; Posterior Scleral Thickness in Perfusion-Fixed Normal and Early-Glaucoma Monkey Eyes. Invest. Ophthalmol. Vis. Sci. 2001;42(13):3202-3208.
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purpose. To characterize posterior scleral thickness in the normal monkey eye
and to assess the effects of acute (15- to 80-minute) and short-term
chronic (3- to 7-week) intraocular pressure (IOP) elevations.
methods. Both eyes of four normal monkeys (both eyes normal) and four monkeys
with early glaucoma (one eye normal and one eye with induced chronic
elevation of IOP) were cannulated. In each monkey, IOP was set to 10 mm
Hg in the normal eye and 30 or 45 mm Hg in the contralateral eye
(normal or early glaucoma) for 15 to 80 minutes. All eight monkeys were
perfusion fixed, yielding eight low IOP–normal eyes, four high
IOP–normal eyes, and four high IOP–early glaucoma eyes. Posterior
scleral thickness was measured histomorphometrically at 15 measurement
points within each eye, and the data were grouped by region: foveal,
midposterior, posterior-equatorial, and equatorial.
results. Overall, posterior scleral thickness was significantly different in the
various regions and among the treatment groups (P < 0.0001). In the low IOP–normal eyes, the posterior sclera was
thickest in the foveal region (307 μm) and thinner in the
midposterior (199 μm), posterior-equatorial (133 μm), and
equatorial (179 μm) regions. In the high IOP–normal and high
IOP–early glaucoma eyes, the posterior sclera was thinner both overall
and within specific regions, compared with the low IOP–normal eyes.
conclusions. The posterior sclera in the perfusion-fixed normal monkey eye thins
progressively from the fovea to the equator and is thinnest just
posterior to the equator. Acute and short-term chronic IOP elevations
cause regional thinning within the posterior sclera of some monkey
eyes, which significantly increases stresses in the scleral
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