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Hosein Hoseini-Yazdi, Stephen J Vincent, Michael J Collins, Scott A Read; Regional changes in human choroidal thickness in response to short-term monocular hemifield myopic defocus. Invest. Ophthalmol. Vis. Sci. 2019;60(9):5236. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
To improve our understanding of the response of the human choroid to defocus, regional changes in choroidal thickness (CT) following short-term monocular hemifield myopic defocus were examined using optical coherence tomography (OCT).
The central 26° visual field of the left eye of 25 healthy young adults (mean age 26 ± 5 years) was exposed to 60 minutes of clear vision (control session), +3 D full-field, +3 D superior retinal hemifield, and +3 D inferior retinal hemifield myopic defocus. Superior and inferior macular CT were examined before and after 60 minutes of defocus using a high resolution, foveal centered vertical OCT line scan, with optical defocus simultaneously imposed on the eye using a Badal optometer and cold mirror system mounted on the OCT instrument (Spectralis). Eye and head movements were monitored during defocus exposure to ensure only half of the visual field beyond the fovea was exposed to defocus during the hemifield defocus sessions, with the fovea and non-defocused field exposed to clear vision.
Superior and inferior CT reduced significantly in the control session (-4 ± 3 μm, p=0.007 and -4 ± 3 μm, p=0.02 respectively). Following full-field myopic defocus, CT increased by +3 ± 9 μm superiorly (p=0.13) and +1 ± 8 μm inferiorly (p=0.75), with the increase in the superior CT being significantly greater than the change in the control session (p=0.004). For the hemifield defocus conditions, when only the superior retina was exposed to myopic defocus, CT increased significantly in the superior region (+7 ± 8 μm, p<0.001), but did not change in the inferior region (+3 ± 9 μm, p=0.12). When only the inferior retina was exposed to myopic defocus, a significant increase in CT was observed inferiorly (+4 ± 8 μm, p=0.005), but there was no change in CT in the superior region (+1 ± 8 μm, p=0.46).
These findings provide evidence supporting a local regional choroidal response to myopic defocus in the human eye, with hemifield myopic defocus leading to significant thickening of the choroid localized to the retinal region exposed to defocus. The magnitude of increase in CT was greater when the superior, rather than inferior or entire 26° central retina was exposed to myopic defocus.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.
Figure 1: Mean change in macular hemiretinal CT following 60 minutes of imposed defocus. Asterisks denote statistically significant change in CT relative to baseline.
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