Sympathetic nervous system activity is associated with choroidal thickness and axial length in school-aged children

Background/aimsWe aim to explore the effect of sympathetic nervous system (SNS) on choroid thickness (ChT) and axial length (AL). MethodsStudents of grade 2 and 3 from a primary school were included and followed for 1 year. Visual acuity, refraction, AL and ChT were measured. Morning urine samples were collected for determining SNS activity by analysing concentrations of epinephrine, norepinephrine and dopamine using the liquid chromatography-tandem mass spectrometry. The most important factor (factor 1) was calculated using factor analysis to comprehensively indicate the SNS activity. ResultsA total of 273 students were included, with an average age of 7.77 +/- 0.69 years, and 150 (54.95%) were boys. Every 1 mu g/L increase in epinephrine is associated with 1.60 mu m (95% CI 0.30 to 2.90, p=0.02) decrease in average ChT. Every 1 mu g/L increase in norepinephrine is associated with 0.53 mu m (95% CI 0.08 to 0.98, p=0.02) decrease in the ChT in inner-superior region. The factor 1 was negatively correlated with the ChT in the superior regions. Every 1 mu g/L increase in norepinephrine was associated with 0.002 mm (95% CI 0.0004 to 0.004, p=0.016) quicker AL elongation. The factor 1 was positively correlated with AL elongation (coefficient=0.037, 95% CI 0.005 to 0.070, p=0.023). ConclusionsWe hypothesised that chronic stress characterised by elevated level of the SNS, was associated with significant increase in AL elongation, probably through thinning of the choroid.