Diurnal Variation in Anterior Segment Angle Structures Using OCT
Narrative Responses:
Purpose
Our objective is to characterize and compare diurnal changes in the anterior chamber angle of healthy subjects using the Anterior Segment OCT.
Methods
Prospective cross-sectional study of 10 healthy subjects with baseline measurements of anterior segment OCT (AS-OCT) with the Visante® OCT, intraocular pressure (IOP), central corneal thickness (CCT), systemic blood pressure, and heart rate (HR) between 8 to 9 am. A follow up measurement of AS-OCT, IOP, blood pressure and HR was done at 3 to 4 pm.
Healthy subjects were not excluded based on gender, age, or race. Refractive errors range from -8 and +8 diopters.
Differences between the afternoon (PM) and morning (AM) measurements were calculated (PM-AM). Paired T-test was used to compare the measurements obtained.
Results
Among 10 subjects with 20 total eyes, the mean IOP change from PM to AM was -0.6 mmHg, p=0.28. However, the difference between PM and AM measurement of AOD 500 (angle opening distance; distance from the anterior iris plane to the posterior corneal surface at 500 µm anterior to the scleral spur) was 71.5 µm, p<0.05. The PM-AM of AOD 750 was 92 µm, p<0.05, and the Angle 500 was 2.45⁰, p<0.05. The ACD PM-AM was -71 µm, p=0.48.
Conclusion
This study suggests a diurnal variation in the angle structures with a larger angle size in the afternoon and narrower angles in the morning. Intraocular pressure did not appear to follow a diurnal pattern in this healthy study population.