advertisement
Abstract #26102 Published in IGR 12-2
Aqueous humor dynamics during the day and night in juvenile and adult rabbits
Zhao M; Hejkal JJ; Camras CB; Toris CBInvestigative Ophthalmology and Visual Science 2010; 51: 3145-3151
PURPOSE: To determine the day and night differences in intraocular pressure (IOP), aqueous flow, outflow facility, uveoscleral outflow, and central corneal thickness (CCT) in juvenile and adult rabbits. METHODS: Studies were performed on twelve 3-month-old and ten 12-month-old male New Zealand White rabbits. Daytime measurements were made between 9 AM (3 hours after lights on) and 3 PM, and nighttime measurements were made between 11 PM and 5 AM. IOP was measured by pneumotonometry and aqueous flow by fluorophotometry. Outflow facility was determined by both fluorophotometry and tonography. Uveoscleral outflow was calculated by the Goldmann equation. CCT was measured by ultrasound pachymetry. Repeated-measures ANOVAs and Student's two-tailed t-tests were used for statistical comparisons. RESULTS: When nighttime versus daytime readings were compared, IOP, aqueous flow and uveoscleral outflow were higher, fluorophotometric outflow facility was lower, and CCT was thinner in both age groups. When the juvenile rabbits were compared to adult rabbits, IOP was lower, aqueous flow and uveoscleral outflow were higher, and fluorophotometric outflow facility and CCT were not different during the day or night. Tonographic outflow facility did not change in a 24-hour period in the juvenile rabbits. CONCLUSIONS: The increased IOP at night in rabbits can be explained mainly by a decrease in outflow facility. An increase in aqueous flow at night is counterbalanced by an increase in uveoscleral outflow. Although the rates of aqueous flow and uveoscleral outflow slow with maturity, their relative day/night differences remain the same.
Department of Ophthalmology and Visual Sciences, University of Nebraska Medical Center, Omaha, Nebraska 68198-5840, USA.
Classification:
6.1.2 Fluctuation, circadian rhythms (Part of: 6 Clinical examination methods > 6.1 Intraocular pressure measurement; factors affecting IOP)
2.6.2 Outflow (Part of: 2 Anatomical structures in glaucoma > 2.6 Aqueous humor dynamics)
2.2 Cornea (Part of: 2 Anatomical structures in glaucoma)
5.3 Other (Part of: 5 Experimental glaucoma; animal models)