Measuring changes in Schlemm’s canal and trabecular meshwork in different accommodation states in myopia children: an observational study

Abstract

Purpose: The aim of the study was to evaluate changes in size of Schlemm’s canal (SC) and trabecular meshwork(TM) in response to accommodation stimuli and cycloplegia states in myopia children. Methods: In total, 34 children were enroled in this study. A −6.0 D accommodation stimulus was achieved by looking at an optotype through a mirror. Cycloplegia state was induced with 1% tropicamide. Two states were confirmed by measuring the central lens thickness (CLT), anterior chamber depth and pupil diameter. The size of SC and TM was measured using swept-source optical coherence tomography. The association between changes in SC size and CLT was analysed. Results: Compared with that in the relaxation state, SC size increased significantly under −6.0 D accommodation stimuli. SC area (SCA) increased from 6371 ± 2517 μm2 to 7824 ± 2727 μm2, SC length (SCL) from 249 ± 10 μm to 295 ± 12 μm and SC width (SCW) from 27 ± 9 μm to 31 ± 8 μm. Under the cycloplegia state, SCA decreased to 5009 ± 2028 μm2; SCL to 212 ± 14 μm, and SCW to 22 ± 5 μm. Changes in SCA (r = 0.35, P = 0.0007), SCL (r = 0.251, P = 0.0172) and SCW (r = 0.253, P = 0.016) were significantly correlated with changes in CLT. TM size was not significantly altered compared to that in the relaxation state. TM length (TML) increased from 562 ± 45 μm to 587 ± 47 μm after exposure to −6.0 D accommodation stimulus. Conclusion: SC size enlarged in response to −6.0 D accommodation stimuli and shrunk under cycloplegia. TM length increased under the accommodation stimulus state.