Application of Angio Optical Coherence Tomography and Flash Electroretinogram in the Study of Retinal Morphology and Function in High Myopia
Authors: Cao Mengdan , Luo Jinxiang , Ouyang Junyi , Nie Fen , Duan Xuanchu 
Published: December 2021

Abstract
Purpose: Using optical coherence tomography (OCTA) and flash electroretinography (F-ERG), we investigated changes to the retinal micromorphology and the overall function of the retina in eyes with different degrees of high myopia. Design: Case-control study. Participants: A total of 64 cases of 118 eyes with axial high myopia with diopters ranging from -−6.0 D to −15.0D were included in the study. The individuals were 18-40 years old.Methods: Subjects were divided into three groups according to the axial length (AL) of the eye and the spherical equivalent (SE)of the lens: the high myopia group (AL: ≤26 mm and SE: −6.0D to −9.0D) with 32 eyes, the ultra-high myopia group (AL: 26-28 mm and SE: -9.25D to -12.0D) with 43 eyes, and the extremely high myopia group (AL: ≥28 mm and SE: −12.25D to −15.0D) with 43 eyes. We used the OCTA measurements macular foveal retinal thickness (MRT), foveal avascular zone (FAZ), and superficial macular and deep retinal microvascular density, and the F-ERG measurements retinal dark-adaptation a-wave and b-wave, oscillation potential (OP) wave, light adaptation a-wave and b-wave, and 30-Hz flicker light amplitudes, which represent the functional state of the retina.Results: The differences in retinal thickness in the macular area between the three groups were only statistically significant within 1 mm of the fovea (P = 0.006). MRT was positively correlated with AL (r = 0.278, P = 0.002) and negatively correlated with SE (R = −0.200, P = 0.031). The difference in the FAZ area between the three groups was also statistically significant (P = 0.036), and FAZ was negatively correlated with AL (r = −0.377, p < 0.001) and positively correlated with SE (r = 0.192, P < 0.5). Both the superficial and deep blood flow density of the macular fovea were positively correlated with AL (p < 0.001). The superficial parafoveal blood flow density was negatively correlated with AL (r = −0.280, P = 0.002) but positively correlated with SE (R = 0.254, P = 0.006). The overall blood flow density of the deep retina, the parafoveal blood flow density, and the blood flow density around the fovea were negatively correlated with AL (p < 0.001) and positively correlated with myopic SE (p < 0.001). The dark-adaptation b-wave, maximum comprehensive response a-wave and b-wave, OP wave, bright-adaptation a-wave and b-wave, and 30-Hz flicker amplitudes of the retina were negatively correlated with AL and positively correlated with SE. The amplitudes of light adaptation a-wave and b-wave were[1] negatively correlated with the foveal avascular density (p < 0.001), and the average amplitude of the OP wave was positively correlated with the superficial retinal avascular density (p < 0.001).Conclusions: Before obvious pathological changes or central vision damage, the morphology and function of the macular area show subtle changes in patients with high myopia. As the degree of myopia increases and the axis of the eye increases, the activity of the cone cells in high myopia eyes decreases and the microvascular circulation in the inner retina and function of inner layer cells, such as non-proa cells, are affected. The changes of retinal dark adaptation are more sensitive than those of bright adaptation, which indicates that retinal rod cell damage may be earlier than cone cell damage in high myopia. Therefore, we believe that the combined use of OCTA and F-ERG can help in the early diagnosis and monitoring of patients at a high risk of myopia and to guide their clinical treatment.Because the p-value is clearly provided, the term “significantly” is not necessary (removed to reduce wordiness).