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Associations between diurnal changes in Goldmann tonometry, corneal geometry, and ocular response analyzer parameters
1School of Optometry and Vision Science, University of New South Wales, Sydney, Australia. wm.lau@unsw.edu.au
Cornea
|March 3, 2012
Summary
Diurnal changes in central corneal thickness and corneal resistance factor influence Goldmann applanation tonometry readings of intraocular pressure. These corneal parameters affect tonometry measurements over a 24-hour period.
Area of Science:
- Ophthalmology
- Optometry
- Biomedical Engineering
Background:
- Intraocular pressure (IOP) is a key metric in glaucoma management.
- Goldmann applanation tonometry (GAT) is a standard method for measuring IOP.
- Corneal properties, such as central corneal thickness (CCT) and biomechanical characteristics, can influence IOP measurements.
Purpose of the Study:
- To examine the relationship between daily fluctuations in GAT-measured IOP.
- To investigate covariations with central corneal thickness (CCT).
- To analyze associations with ocular response analyzer (ORA) parameters like corneal hysteresis (CH) and corneal resistance factor (CRF).
Main Methods:
- Twenty-five healthy subjects underwent repeated measurements over 24 hours.
- Included Goldmann applanation tonometry (GAT), central corneal thickness (CCT), and ocular response analyzer (ORA) assessments.
- Measurements were taken at regular intervals throughout the day and night.
Main Results:
- GAT measurements showed a maximum variation of 2.5 mm Hg over 24 hours.
- Diurnal changes in CCT and CRF significantly predicted fluctuations in GAT readings (P < 0.01).
- Corneal hysteresis and CRF also varied with CCT throughout the day.
Conclusions:
- Diurnal variations in corneal parameters (CCT, CRF) partially explain the 24-hour variability in GAT IOP measurements.
- This suggests corneal properties significantly impact tonometry accuracy.
- Corneal resistance factor may also be influenced by IOP levels.
