Choroidal Thickness and Correlations with Intraocular Pressure and Spherical Equivalent in Young Myopic Eyes without Maculopathy

Background: Refractive error is one of the causes of visual impairment worldwide, among which myopia is the most common. Myopia is prevalent worldwide, particularly in East and Southeast Asia, which have myopia prevalence rates of approximately 80-90% and high myopia prevalence rates of 10-20% in young adults. High myopia is closely related to a variety of pathological changes and a higher risk of blinding complication. Purpose: To identify the distribution of choroidal thickness (CT) and to determine whether there are associations between subfoveal choroidal thickness (SFCT) and intraocular pressure (IOP) and spherical equivalent (SE) in young healthy myopes without maculopathy. Methods: A total of 116 young subjects without maculopathy were recruited in this study and underwent comprehensive ophthalmic examinations. Enhanced depth imaging spectral domain optical coherence tomography was performed for CT measurement and assessment. SFCT, as well as CT at 3 mm nasal, temporal, superior and inferior to fovea were measured. Univariable linear regression analysis and Multiple regression analysis were used to study the correlation between SFCT and spherical equivalent (SE) as well as IOP. To assess the CT at each location and explore it’s associated factors. Results: The SFCT of high myopes was notably thinner (197.00±35.21 µm) compared with mild myopes (287.05±68.31 µm) and moderate myopes (251.13±64.40µm). For all three groups, CT at 3 mm nasal was the thinnest (195.21±52.43µm, 168.43±59.24µm, 129.56±30.97µm, respectively.) Univariable linear regression analysis indicated that SFCT decreased by 15.49 µm per diopter in myopic refractive change (P <0.001, R2 = 0.146) and decreased by 17.87 µm per 1mmHg increase inintraocular pressure (IOP) (P < 0.001, R2 = 0.440). Multiple regression analysis indicated that there were significantly correlations between SFCT and spherical equivalent (SE) as well as IOP in mild myopes and moderate myopes, but not in high myopes. Conclusions: A significant difference of the CT distribution was found in the centre region among myopes. However, nasal choroid thinning was the most obvious in all myopia groups. SFCT was significantly correlated with IOP and SE in the myopic population. However, the same correlation was not observed in young highly myopic eyes.