ObjectiveTo investigate the changes of choroid thickness in adolescents with different types of non-pathological high myopia (HM). MethodsA retrospective observational study. From January 2021 to April 2022, 179 eyes of 101 adolescents with myopia in Liaocheng Aier Eye Hospital were collected and analyzed. According to the spherical equivalent (SE) and corneal curvature, subjects were divided into mild myopia or emmetical eye group (control group), HM group, occult HM group (OHM group) and super HM group (SHM group). There were 52 eyes in 30 cases, 47 eyes in 26 cases, 42 eyes in 24 cases and 38 eyes in 21 cases, respectively. Medical optometry, intraocular pressure, optical coherence tomography (OCT), axial length (AL) and corneal curvature were measured. The macular foveal choroidal thickness was analyzed by using spectral-domain OCT. The diopter was expressed in SE. The thickness of choroid in the fovea of macular region was measured by enhanced deep imaging with frequency domain OCT. The thickness of choroid was measured in 9 regions within 1 mm, 3 mm from the fovea, including the upper, lower, nasal and temporal regions. Generalized estimating equation was used to compare the data among groups, and the least significant difference t-test was used to compare the data among groups. The correlation between AL, corneal curvature, intraocular pressure and choroidal thickness was analyzed by Pearson correlation. ResultsThe choroidal thickness in the foveal macula and the areas 1 mm and 3 mm away from the fovea were compared among the control group, HM group, OHM group and SHM group, the difference were significant (χ2=76.646, 36.715, 27.660, 35.301, 24.346, 38.093, 36.275, 33.584, 36.050; P＜0.05). Compared with the control group, the choroidal thickness of the fovea and the choroidal thickness in each area within 1 and 3 mm from the fovea in the HM group, the OHM group and the SHM group were significantly thinner than those in the control group, and the difference was statistically significant (P＜0.05). There were statistically significant differences in choroidal thickness in each region between the group and the SHM group, and between the OHM group and the SHM group (P＜0.05). The results of correlation analysis showed that AL was negatively correlated with choroidal thickness in various regions (P＜0.05); SE was positively correlated with choroidal thickness in various regions (P＜0.05); corneal curvature and intraocular pressure had no significant correlation with choroidal thickness in various regions (P＞0.05). ConclusionsThe choroidal thickness of SHM is significantly lower than that of OHM and HM; OHM patients have lower SE. However, the choroidal thickness is significantly thinner. AL and SE are the influencing factors of choroidal thickness.