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Muteb Alanazi,1,2 Patrick Caroline,2 Amane Alshamrani,2 Turki Alanazi,3 Maria Liu4 1Optometry Department, College of Applied Medical Sciences, King Saud University, Riyadh, Saudi Arabia; 2College of Optometry, Pacific University, Forest Grove, OR, USA; 3School of Engineering and Applied Science, The George Washington University, Washington, DC, USA; 4UC Berkeley School of Optometry, Berkeley, CA, USACorrespondence: Muteb Alanazi Tel +966 5651227716Email mkalanazi@ksu.edu.saPurpose: To examine the regional distribution of choroidal thickness (ChT) and the diurnal variation in ChT and axial length (AL) over a wide range of myopic refractive error.Methods: ChT was measured in thirty-four healthy young adults (age mean ± SD: 25.2 ± 2.8, range: 18â 35 years) using spectral-domain optical coherence tomography and AL using an IOL-Master 500. Participants were divided into three refractive groups: emmetropes, myopes, and high myopes. We evaluated ChT in macular (foveal, parafovea, and perifovea) and peripheral regions (6-mm from the foveal pit) in four quadrants (superior, temporal, inferior, and nasal). To assess the diurnal variation, three measurement sessions of ChT and AL were taken at 8 AM, 12 PM, 4 PM.Results: ChT thins progressively towards the periphery. Superior and nasal quadrants exhibited the thickest (277 ± 73 μm) and thinnest (218 ± 89 μm) choroid, respectively. Higher myopic eyes showed an overall thinner choroid (237 ± 48 μm) compared to myopic eyes (264 ± 78 μm) (P < 0.05). Higher myopes exhibited a significant choroidal thinning in all quadrants except in the temporal quadrant (all p < 0.05). Both ChT and AL underwent a significant diurnal variation (p < 0.05). The ChT and AL diurnal variation amplitudes in higher myopes were significantly reduced (ChT: 14.6 ± 11, AL: 14.5 ± 13 μm), compared to those in emmetropes (ChT: 21.4 ± 15, AL: 21.3 ± 8.5 μm) and myopes (ChT: 19 ± 17, AL: 19 ± 9.7 μm). Diurnal variation amplitude in ChT did not differ significantly across quadrants and choroidal eccentricity regions (p > 0.05).Conclusion: ChT distribution varies based on quadrant and eccentricity; superior choroid exhibited the thickest, and nasal showed the thinnest choroid. Higher myopes experience a reduced diurnal variation in ChT and AL.Keywords: choroid, diurnal variation, myopia, optical coherence tomography |
