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Li-Fang Hung, Josh Wallman, Earl L. Smith; Vision-Dependent Changes in the Choroidal Thickness of Macaque Monkeys. Invest. Ophthalmol. Vis. Sci. 2000;41(6):1259-1269.
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To determine whether changes in the eye’s effective refractive state
produce changes in the thickness of the choroid in infant monkeys.
Normal developmental changes in choroidal thickness were studied in 10
normal rhesus monkeys. Hyperopia or myopia was induced by rearing 26
infant monkeys with either spectacle or diffuser lenses secured in
front of one or both eyes. The treatment lenses were worn continuously
beginning at approximately 3 weeks of age for an average of 120 days.
Refractive status and ocular axial dimensions, including choroidal
thickness, were measured by retinoscopy and high-frequency A-scan
Three lines of evidence indicate that the normal increase in choroidal
thickness that occurs during early maturation can be altered by the
eye’s refractive state. First, in monkeys experiencing form
deprivation or those in the process of compensating for imposed optical
errors, choroidal thickness and refractive error were significantly
correlated with eyes developing myopia having thinner choroids than
those developing hyperopia. Second, the choroids in eyes recovering
from binocularly induced myopia increased in thickness at a faster rate
than the choroids in recovering hyperopic eyes. Third, monkeys
recovering from induced anisometropias showed interocular alterations
in choroidal thickness that were always in the appropriate direction to
compensate for the anisometropia. These changes in choroidal thickness,
which were on the order of 50 μm, occurred quickly and preceded
significant changes in overall eye size.
Changes in the eye’s effective refractive state produce rapid
compensating changes in choroidal thickness. Although these choroidal
changes are small relative to the eye’s refractive error, they may
play an important role in the visual regulation of axial growth
associated with emmetropization.
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