Background To determine whether dynamic changes in choroidal thickness (CT) cause shallowing of the anterior chamber.
Methods 34 healthy volunteers were enrolled. The participants in our study adopted the upside-down position for 1.5 min, which was the model we used to study the dynamic changes in CT. Intraocular pressure (IOP) elevation, optical coherence tomography images of the choroid and anterior chamber were obtained at baseline, after being in an upside-down position in an inversion machine and after 15 min of rest. The changes in IOP, anterior chamber and choroidal blood flow between the baseline and the upside-down position were compared.
Results Sixty-eight eyes from 34 subjects were analysed. After being in upside-down position for 1.5 min, there was a significant increase in CT from 226.39±52.44 µm to 238.34±54.84 µm (p<0.001). Choroidal flow index decreased from 0.3357±0.0251 to 0.3004±0.0190 in upside-down position, and there was a decrease in anterior chamber depth (3.21±0.22 mm to 3.13±0.21 mm, p<0.001) and angle opening distance at 500 µm from the scleral spur (0.65±0.24 mm to 0.58±0.20 mm, p=0.007). Pearson correlation analysis showed that the increase in CT was positively related with CT at baseline CT (p=0.001).
Conclusion When the body position changed from sitting to upside-down position, there was choroidal thickening, anterior chamber shallowing and IOP elevation with reduced choroidal blood flow. The data provide evidence about the relationship between choroid expansion and shallowing of the anterior chamber, which may be of relevance for the pathogenesis of angle closure.
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Correction notice This paper has been amended since it was published online. The fifth author's name was switched and should be Tin Aung.
Contributors Concept and design: FL, XZ and AT. Data collection: FL and HL. Data analysis: FL, JY and JL. Manuscript writing: FL, JY, AT and XZ.
Funding The study was funded by the National Key R&D Program of China (2018YFC0116500), the Science and Technology Program of Guangzhou, China (201803010066), the Science and Technology Planning Projects of Guangdong Province (2017B030314025) and the Fundamental Research Funds of the State Key Laboratory of Ophthalmology.
Competing interests None declared.
Patient consent for publication Obtained.
Ethics approval The study was approved by the ethical review committee of the Zhongshan Ophthalmic Center.
Provenance and peer review Not commissioned; externally peer reviewed.
Data availability statement Data are available upon request.
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