Diurnal Variation in Anterior Segment Angle Structures Using OCT

Friday, April 25, 2014
KIOSKS (Boston Convention and Exhibition Center)
Anna C. Kupcha Dallas, TX, USA
Allen S. Wang, MD Dallas, TX, USA
Zachary D. Vest, MD, Colorado Eye Institute, Colorado Springs, CO, USA
Jess T. Whitson, MD, UT Southwestern Medical Center, Dallas, TX, USA

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.