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J.A. Rada, L. Palmer; Choroidal Permeability Changes Correlate With Rate of Scleral Proteoglycan Synthesis During the Recovery From Induced Myopia . Invest. Ophthalmol. Vis. Sci. 2006;47(13):1803.
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© ARVO (1962-2015); The Authors (2016-present)
Previous work in our lab has shown that the chick choroid of recovering eyes releases factors that have an inhibitory effect on scleral proteoglycan synthesis in vitro. The present study was undertaken to determine whether increases in choroidal permeability can negatively regulate scleral proteoglycan synthesis in vivo, presumably through the release of scleral growth inhibitors.
Form deprivation myopia was induced in chicks for 10 days followed by a period of unrestricted vision for 1 – 15 days (recovery). Choroidal permeability was quantified by measuring albumin leakage from choroidal blood vessels into suprachoroidal fluid using Evans blue. Scleral proteoglycan synthesis was assessed on punches of sclera obtained immediately after extraction of suprachoroidal fluid for permeability measurements, by measuring the amount of 35SO4 incorporated into glycosaminoglycans over a period of 4 hr at 37°C.
No significant differences in choroidal permeability or scleral proteoglycan synthesis were detected in treated eyes as compared to controls following 1 day of recovery (p = 0.135 and p = 0.772, respectively). Following 4 days of recovery, choroidal permeability was significantly elevated in recovering eyes as compared with contralateral controls (0.2245 ± 0.02 mg/ml as compared with 0.0202 ± 0.0056,repectively, p < 0.01; paired t–test) and the rate of scleral proteoglycan synthesis was significantly lower in recovering eyes as compared with control eyes (p<0.05, paired t–test). Evans blue levels remained elevated in suprachoroidal fluid of recovering eyes following 7 days of recovery (p< 0.05) but returned to levels similar to controls following 15 days of recovery (p = 0.108). Following 7 and 15 days of recovery, scleral proteoglycan synthesis rates in recovering eyes were similar to controls. Comparison of choroidal permeability changes in recovering eyes with that of scleral proteoglycan synthesis rates over the 15 day recovery period suggests that increased choroidal permeability coincides with a significant reduction in scleral proteoglycan synthesis in the posterior sclera (r2 = 0.4939; p <0.01, ANOVA).
The results of this study suggest that increased choroidal permeability during the recovery from myopia may be responsible for slowing vitreous chamber elongation through the inhibition of proteoglycan synthesis in the posterior sclera.
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