![]() ![]() However, little is known about the inter-device variability in choroidal thickness measurements in children eyes. Many studies comparing the two commonly used generations of OCTs (SD-OCT and SS-OCT) have been focusing on either normal 9, 10, 11, 12, 13, 14, 15, 16 or diseased 12, 15, 17, 18 adult eyes. Nevertheless, it is still questionable whether measurements made by SD-OCT and SS-OCT images are interchangeable. Owing to the advantage of greater scanning depth and availability of commercialised SS-OCT, many researchers have switched from SD-OCT to SS-OCT in assessing deep structures like choroid. By employing light beam with a longer wavelength, SS-OCT could provide a higher quality of choroid imaging by having less signal noise and better penetration in deeper structures 5, 6, 7. Whereas swept-source optical coherence tomography (SS-OCT), the newer generation of OCT, uses a tunable laser beam to sweep across various layers with a single photodiode detector. Using the enhanced depth imaging (EDI) mode with spectral-domain optical coherence tomography (SD-OCT), peak sensitivity of measurements is positioned at the inner sclera, enabling visualisation of deeper tissue layers including choroidal structure 5, 6, 7, 8. Accurate and reliable monitoring of temporal changes in choroidal thickness may help in studying the role of choroid in myopia. Therefore, choroidal changes since childhood may be an early indictor in myopic development. Consistent evidence has shown the close link between myopia and choroidal thinning in both children and adults 1, 2, 3, 4. Longitudinal studies of choroid in children suggest its role in eye development, including emmetropisation, growth factor secretion and scleral growth modulation 1, 2.Īssociations of choroidal thickness as measured by optical coherence tomography (OCT) have been reported for retinal pathologies, including myopia. It is crucial in thermoregulation, regulation of intraocular pressure (IOP) and drainage of aqueous humor. The highly-vascularised choroid is the middle tunic of the eye, supplying nearly 90% of ocular artery blood flow. Therefore, the measurements are not interchangeable. In conclusion, intra-class correlation coefficient (ICC) shows an acceptable agreement between SD-OCT and SS-OCT, however, there was a significant inter-device difference of choroidal thickness measurements in normal children eyes. Validated conversion equation for translating SD-OCT CFCT measurement into SS-OCT was SS-OCT = 35.261 + 0.810 × SD-OCT. Bland–Altman limit of agreement on the relative difference scale for SD-OCT/SS-OCT was 86.33 μm. However, choroidal thickness obtained by SD-OCT was significantly thicker than that measured by SS-OCT with a mean difference of 21.40 ± 33.13 μm ( P < 0.001). The central foveal choroidal thickness (CFCT) measured by SD-OCT and SS-OCT was 273.24 ± 54.29 μm and 251.84 ± 47.12 μm respectively. A total of 114 children from the population-based Hong Kong Children Eye Study with mean age of 7.38 ± 0.82 years were included. Choroidal thickness of the right eye was measured by both devices. Hence, we compared choroidal thickness measurements between spectral-domain optical coherence tomography (SD-OCT) and swept-source optical coherence tomography (SS-OCT) in healthy paediatric eyes. Choroidal thickness is associated with many ocular conditions, interchangeability among different generations of optical coherence tomography is therefore important for both research purpose and clinical application.
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