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

Abstract

Purpose: Studies were designed to evaluate changes in the size of the Schlemm's Canal (SC) and trabecular meshwork(TM) during accommodation stimuli and cycloplegia states in myopic children. Methods: 34 children were enrolled. A-6D 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) , the anterior chamber depth and the pupil diameter. The size of the Schlemm's Canal (SC) and Trabecular Meshwork(TM) was measured using swept-source optical coherence tomography. And the associations between the change of the SC and the CLT were analyzed. Results: When compared with the relaxation state, under-6D accommodation stimuli, the size of SC increased significantly: the SC area (SCA) amplified from 6371±2517μm 2 to 7824±2727 μm 2 ; the SC length (SCL) from 249±10 μm to 295±12 μm, and SC width (SCW) from 27±9 μm to 31±8 μm. Under cycloplegia state, the SCA reduced to 5009±2028 μm 2 ; the SCL to 212±μm and the SCW to 22±5 μm. In addition, the changed areas of 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 the change in CLT. However, the size of TM did not change substantially when compared with the relaxation state. Only the TM length (TML) increased from 562±45μm to 587±47μm after-6D accommodation stimulus. Conclusion: SC size enlarges after-6D accommodation stimuli and shrinks under cycloplegia. However, for TM, only the TM length increase under accommodation stimulus state.

Quantitative analysis of internal components of the human crystalline lens during accommodation in adults

“…All measurement items were sequentially measured under three different accommodation conditions (0D, − 3D, − 6D accommodation). As we did before, the images of these eyes were analyzed by two observers who were blinded to treatments, the intraobserver reproducibility and interobserver reproducibility were also evaluated 27 . O nly those testing items whose intraclass correlation coefficient value is not less than 0.75 will be presented.…”

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

“…In postlensectomy eyes, accommodative effort does not increase SC dimensions [3]. The mechanism is different from the one reported by Xiang et al, who administered tropicamide to paralyse the ciliary muscle [1]. After lensectomy, ciliary muscle contraction in response to attempted accommodation is preserved, but SC response is reduced or absent, possibly due to post-surgical inflammatory and mechanical changes leading to trabecular meshwork damage and stiffness.…”

“…We read with interest the article "Measuring changes in Schlemm's canal and trabecular meshwork in different accommodation states in myopia children" by Xiang et al [1]. We congratulate the authors on their elegant description of changes in Schlemm canal (SC) length and crosssectional area (CSA) associated with accommodation in 34 children aged 7-14 years with myopia.…”

Dynamic Changes of Scleral Spur Length In Different Accommodation States

“…According to the individual interpupillary distance and testing items adjusted the tilting angle of the mirror. The participants were instructed to stare at the optotypes through the mirror with their left eye under the 0D, -4D and the − 8.0 D accommodation (distance based on the formula: 100/−(− M + X) cm, where X was the refractory error value in diopters, M is the accommodative response) 20 stimulation state, and right eye was covered with a gauze. According to the recommendations of Gabriel, the mean of each 5 s was determined for both accommodative response and pupil size 21 .…”