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Neville A. McBrien, Lynn M. Cornell, Alex Gentle; Structural and Ultrastructural Changes to the Sclera in a Mammalian Model of High Myopia. Invest. Ophthalmol. Vis. Sci. 2001;42(10):2179-2187. doi: https://doi.org/.
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purpose. The development of high myopia is associated with scleral thinning and
changes in the diameter of scleral collagen fibrils in humans. In the
present study, the association between these scleral changes and the
losses in scleral tissue that have previously been reported in animal
models were investigated to determine the relationship between changes
in collagen fibril architecture and thinning of the sclera in high
methods. Myopia was induced in young tree shrews by monocular deprivation of
pattern vision for short-term (12 days) or long-term (3–20 months)
periods. Scleral tissue from normal animals over a wide age range
(birth to 21 months) was also collected to provide data on the normal
development of the sclera. Light and electron microscopy were used to
measure scleral thickness and to determine the frequency distribution
of collagen fibril diameters in the sclera. Tissue loss was monitored
through measures of scleral dry weight.
results. Significant scleral thinning and tissue loss, particularly at the
posterior pole of the eye, were associated with ocular enlargement and
myopia development after both short- and long-term treatments. However,
collagen fibril diameter distribution was not significantly altered
after short-term myopia treatment, whereas, from 3 months of monocular
deprivation onward, significant reductions in the median collagen
fibril diameter were noted, particularly at the posterior pole.
conclusions. The results of this study demonstrated that loss of scleral tissue and
subsequent scleral thinning occurred rapidly during development of
axial myopia. However, this initial tissue loss progressed in a way
that did not result in significant alterations to the collagen fibril
diameter distribution. In the longer term, there was an increased
number of small diameter collagen fibrils in the sclera of highly
myopic eyes, which is consistent with findings in humans and is likely
to contribute to the weakened biomechanical properties of the sclera
that have previously been reported.
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