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Srinivas R. Sadda, Colin S. Tan, Yanling Ouyang, Humberto Ruiz-Garcia; Diurnal Variation of Choroidal Thickness in Normal Healthy Subjects. Invest. Ophthalmol. Vis. Sci. 2012;53(14):1757.
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The choroid is believed to play an important role in the physiology of the eye and in the pathogenesis of a variety of ocular diseases. Variation in choroidal thickness over time and with time of day has not been studied using Spectral Domain Optical Coherence Tomography (SD-OCT). We aimed to describe the pattern and magnitude of diurnal variation of choroidal thickness (CT), its relation to systemic and ocular factors, and to determine the inter-visit reproducibility of diurnal patterns.
A prospective study was conducted on 12 healthy volunteers who each underwent sequential ocular imaging on 2 separate days at 5 fixed, two-hourly time intervals. SD-OCT with Enhanced Depth Imaging and image tracking was performed using a standardized protocol. Choroidal and retinal thicknesses were independently assessed by 2 masked graders. CT diurnal variation was assessed using repeated measures Analysis of Variance (ANOVA).
A significant diurnal variation in CT was observed, with mean maximum CT of 372.2µm, minimum of 340.6µm (p<0.001), and mean diurnal amplitude of 33.7µm. Retinal thickness (mean 235.0µm) did not exhibit significant diurnal variation (p=0.621). The amplitude of CT variation was significantly greater for subjects with thicker morning baseline CT compared to those with thin choroids (43.1µm vs. 10.5µm, p<0.001). There were significant correlations between CT and age (p=0.032), axial length (p<0.001) and spherical equivalent (p<0.001). The change in CT also correlated with change in systolic blood pressure (p=0.031). Comparing CT on 2 different days, a similar diurnal pattern was observed, with no significant difference between corresponding measurements at the same time points (p=0.180).
There is significant diurnal variation of CT, with good inter-visit reproducibility of diurnal patterns on 2 different days. The amplitude of variation varies with morning baseline CT, and is correlated with age, axial length, refractive error and change in systolic blood pressure.
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