Retinal Vessel Parameters and Choroidal Thickness using Optical Coherence Tomography and OCT Angiogram in Normal Children: A Cross-sectional Study

Abstract

Introduction: Optical Coherence Tomography (OCT) and OCT Angiogram (OCT-A) are non invasive techniques for imaging the microvasculature of retina and choroid. OCT is a method of analysing the in-vivo retinal architecture. OCT uses low coherence interferometry to create a cross-sectional map of the retina with a resolution of 10-15 µm. Swept Source OCT utilises light source of 1050 nm wavelength and can reproducibly measure choroidal thickness. OCT-A uses the principle of motion contrast, where the moving red blood cells are traced to depict vessels through different segments of the retina. The same tissue area is imaged repeatedly and differences are analysed between scans to detect area with high flow rates, low flow and no flow at all. Only a few studies have been reported on baseline choroidal thickness and retinal vessel parameters in children. This study was conducted to measure these parameters using Swept source OCT in normal children. Aim: To measure retinal vasculature parameters and choroidal thickness using OCT and OCT-A in normal children. Materials and Methods: A cross-sectional study was conducted on 68 children between 5-15 years of age in Department of Ophthalmology, Christian Medical College and Hospital, Vellore, Tamil Nadu, India between February 2018 to July 2018, after obtaining the Ethical clearance from the Institutional review board. The children were divided into two groups, 5-10 years and >10-15 years. Children with Best Corrected Visual Acuity (BCVA) <6/6, axial length< 20/ >25 mm, any systemic disease or ocular pathology were excluded. All underwent comprehensive ophthalmic examination along with fundus photography, OCT and OCTA imaging. Retinal artery and vein calibre at the disc margin and Subfoveal Choroidal Thickness (SFCT) were measured. Measurement of Foveal Avascular Zone (FAZ) both superficial and deep, vascular density (VD) of perifoveal, papillary and peripapillary area were obtained from OCT-A. T-test was used to compare the parameters with p value <0.05 considered as significant. Results: A total of 136 eyes were included. Mean retinal artery measured at superior and inferior disc margin was 176.84±43.88 µm and 177.78±41.69 µm respectively. Mean retinal vein measured at superior and inferior disc margin was 218.90±46.36 µm and 235.37±48.07 µm respectively. Perifoveal images were clear and vessel densities could be anlaysed but papillary and peripapillary vessel densities were not analysed due to poor image quality in many subjects. The mean retinal artery caliber in the age group 5-10 years was 179.85±45.62 µm and 174.00±42.30 µm in the age group >10-15 years at the superior disc margin with p-value of (0.4403). There was no statistical difference retinal vessel caliber between the two groups. The mean SFCT in the 5-10 years group was 344.42±86.77 µm and 343.40± 93.56 µm in the other with a p value 0.9474. The mean superficial FAZ (SFAZ) was189.79±117.11 µm2 in the first group and 264.88±169.91 µm2 in the second group,( p=0.0034). There was no statistical difference among these parameters between the two groups except SFAZ, p=0.0034. Conclusion: Present study describes the normative data on retinal vasculature parameters and choroidal thickness in Indian paediatric population aged 5 to 15 years using OCT and OCT-A. The study findings will further help in screening and monitoring the subjects in this age group.