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ABSTRACT
Purpose: To assess 24-hour fluctuations in Schlemm’s canal (SC) parameters (cross-sectional area, perimeter) and intraocular pressure (IOP) and the relationship between these fluctuations in healthy individuals.
Methods: SC and IOP were examined in 29 participants at 2:30, 5:30, 11:30, 17:30, and 23:30 within one day. The superior, inferior, nasal, and temporal SC quadrants were evaluated using 80-MHz ultrasound biomicroscopy.
Results: SC parameters and IOP fluctuated significantly within 24 hours (all P < 0.05). After age, gender, axial length, and central corneal thickness were adjusted, compared with the baseline (23:30) value, the change in SC cross-sectional area was negatively associated with the change in IOP at 2:30, 5:30, 11:30, and 17:30 (β = −0.072[−0.094, −0.049], −0.070[−0.102, −0.038], −0.046[−0.079, −0.013], and −0.033[−0.062, −0.004], respectively; P < 0.001, < 0.001, = 0.009, and = 0.028, respectively). The nasal (175.6 ± 36.0 pixels) and inferior (174.8 ± 36.0 pixels) SC cross-sectional areas were significantly larger than the superior area (156.2 ± 27.1 pixels) (P = 0.018 and 0.048, respectively) at 23:30. The observable SC proportion did not change among the quadrants or measurement time points (all P > 0.05).
Conclusions: SC cross-sectional area fluctuated throughout the day and was negatively associated with changes in IOP.
Declaration of interest
The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.
Funding
Supported by the National Natural Science Foundation of China (81471744). The authors report no commercial relationship existed in the form of financial support or personal financial interest.