Diurnal Variations in the Morphology of Schlemm's Canal and Intraocular Pressure in Healthy Chinese: An SS-OCT Study.
Gao Kai, Li Fei, Aung Tin, Zhang Xiulan
AI Summary
This study found Schlemm's Canal (SC) changes negatively correlated with IOP fluctuations only in the inferior quadrant of healthy eyes. SC imaging could help understand IOP changes and glaucoma.
Abstract
Purpose
To characterize the diurnal variations in the dimensions of the Schlemm's canal (SC) and its association with intraocular pressure (IOP) using swept-source optical coherence tomography (SS-OCT).
Methods
The temporal, nasal, inferior, and superior limbus of 102 eyes of 51 healthy subjects were imaged in vivo by SS-COT at 5 time points of 8 AM, 11 AM, 2 PM, 5 PM, and 8 PM. IOP was measured at the same time by Goldmann applanation tonometry (GAT). The diameter and the cross-sectional area of the SC were measured in ImageJ. The associations between changes in the SC parameters, IOP, and other biometric parameters were determined using a general estimating equations model. The temporal and inferior limbus of 94 eyes of 47 healthy subjects were also imaged before and during the Valsalva maneuver (VM) at 8 PM.
Results
Mean IOPs at different time points were 13.37, 12.89, 11.9, 12.02, and 12.36 mm Hg. Of all four quadrants, the detectable rate of SC was highest in the superior quadrant (85.3%) and lowest in the inferior quadrant (75.5%). We found that changes in the SC area and diameter were negatively associated with IOP changes only in the inferior quadrant (P = 0.0046 and P = 0.0332, respectively), after adjusting for age, sex, eye, spherical equivalent, and axial length. The mean SC area and diameter during the VM were significantly higher than prior to the VM (P < 0.001).
Conclusions
The changes in the SC parameters were negatively associated with IOP changes only in the inferior quadrant. The VM could expand the SC in healthy subjects. Imaging of the SC may be a useful method to discover the reason why IOP fluctuates, and how SC changes morphologically during the daytime in the future.
MeSH Terms
Shields Classification
Key Concepts4
In a cross-sectional study of 102 eyes of 51 healthy Chinese subjects, changes in the Schlemm's canal (SC) area and diameter were negatively associated with intraocular pressure (IOP) changes only in the inferior quadrant (P = 0.0046 and P = 0.0332, respectively), after adjusting for age, sex, eye, spherical equivalent, and axial length.
In a cross-sectional study of 94 eyes of 47 healthy Chinese subjects, the mean Schlemm's canal (SC) area and diameter during the Valsalva maneuver (VM) were significantly higher than prior to the VM (P < 0.001), indicating that the VM could expand the SC.
In a cross-sectional study of 102 eyes of 51 healthy Chinese subjects, the mean intraocular pressures (IOPs) at 8 AM, 11 AM, 2 PM, 5 PM, and 8 PM were 13.37, 12.89, 11.9, 12.02, and 12.36 mm Hg, respectively.
In a cross-sectional study of 102 eyes of 51 healthy Chinese subjects, the detectable rate of Schlemm's canal (SC) using swept-source optical coherence tomography (SS-OCT) was highest in the superior quadrant (85.3%) and lowest in the inferior quadrant (75.5%).
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