Abstract
The current study aimed to examine the short-term choroidal response to optical defocus in schoolchildren. Myopic schoolchildren aged 8–16 were randomly allocated to control group (CG), myopic defocus group (MDG) and hyperopic defocus group (HDG) (n = 17 per group). Children in MDG and HDG received additional +3D and -3D lenses, respectively, to their full corrections on the right eyes. Full correction was given to their left eyes, and on both eyes in the CG. Axial length (AXL) and subfoveal choroidal thickness (SFChT) were then measured by spectral domain optical coherence tomography. Children wore their group-specific correction for 2 hours after which any existing optical defocus was removed, and subjects wore full corrections for another 2 hours. Both the AXL and SFChT were recorded hourly for 4 hours. The mean refraction of all subjects was -3.41 ± 0.37D (± SEM). SFChT thinned when exposed to hyperopic defocus for 2 hours but less thinning was observed in response to myopic defocus compared to the control group (p < 0.05, two-way ANOVA). Removal of optical defocus significantly decreased SFChT in the MDG and significantly increased SFChT in the HDG after 1 and 2 hours (mean percentage change at 2-hour; control vs. hyperopic defocus vs. myopic defocus; -0.33 ± 0.59% vs. 3.04 ± 0.60% vs. -1.34 ± 0.74%, p < 0.01). Our results showed short-term exposure to myopic defocus induced relative choroidal thickening while hyperopic defocus led to choroidal thinning in children. This rapid and reversible choroidal response may be an important clinical parameter in gauging retinal response to optical defocus in human myopia.
Highlights
The choroid is the posterior part of the uveal tract in the eye and it supplies nutrients and oxygen to the outer retina and modulates retinal temperature [1]
After two hours of exposure, Axial length (AXL) increased and subfoveal choroidal thickness (SFChT) decreased in the group with hyperopic defocus
In young emmetropic adults receiving the same amount of myopic defocus for an hour choroidal thickness increased by approximately 12 μm compared to baseline [27]
Summary
The choroid is the posterior part of the uveal tract in the eye and it supplies nutrients and oxygen to the outer retina and modulates retinal temperature [1]. Defocus and Choroidal Thickness Changes in Children the choroid will thicken again and return to baseline values [5] This choroidal expansion was shown to occur within minutes in chicks [6]. Choroidal permeability has been investigated most extensively in chicks because their change in choroidal thickness during ocular development is the most pronounced across a range of animals and their choroidal vessels have a lymphatic vessel-like structure. The protein concentration of the suprachoroidal fluid was significantly up-regulated during recovery from myopia [9, 10] indicating an increase in choroidal permeability. These results suggest a role for the choroid in the regulation of eye growth
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