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Jinhua Bao, Bjorn Drobe, Ke Chen, Hao Chen; Transient changes in choroidal thickness to different levels of imposed myopic defocus. Invest. Ophthalmol. Vis. Sci. 2014;55(13):3600. doi: https://doi.org/.
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To investigate short-term changes in choroidal thickness and other ocular biometrics to imposed myopic defocus in young adults.
Ocular biometrics of thirteen myopic young adult subjects was measured before and after 60 minutes of exposure to monocular defocus (right eye) while watching movies on a 5.5m distant screen. Choroidal and retinal thicknesses were measured by means of Lenstar SD-OCT (Heidelberg Spectralis OCT; Heidelberg Engineering, Heidelberg, Germany) and axial length by Lenstar LS 900 optical biometer (Lenstar LS 900; Haag Streit AG, Koeniz, Switzerland). Four different monocular defocus conditions were tested, each on a separate day: control (no defocus) and myopic defocus (+1D, +3D and +5D defocus). The fellow eye was optimally corrected for distance (no defocus).
After 60 minutes, choroidal thickness of the right eye exhibited a significant increase only for +3D and +5D defocus conditions (mean change, +1D: +7.53±7.80μm, p>0.05; +3D: +12.51±11.23μm, p=0.002; +5D: +11.74±8.45μm, p<0.001). Retinal thickness exhibited no significant change with any myopic defocus conditions (mean change, +1D: -1.17±2.52μm, +3D: -1.93±1.99μm, +5D: -1.77±3.49 μm; p>0.1). Optical axial length decreased significantly only after +5D defocus condition (mean change, +1D: +2.13±9.67μm, p>0.1; +3D: -1.93±9.05μm, p>0.1; +5D: -6.56±9.14μm, p=0.024). Choroidal thickness, retinal thickness and axial length of the left eye showed no significant change (p>0.05).
Significant increase in choroidal thickness occurred in human subjects after 60 minutes of myopic defocus of 3D or more but not in axial length. Moreover, there is no evidence to support the notion that choroidal thickness elongation is proportional to the degree of myopic defocus.
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