Abstract
Purpose:
The magnitude of change in intraocular pressure (IOP) with change in body posture is not routinely considered in clinical glaucoma practice. It has been reported using different tonometers with very different results. This study presents a direct comparison of 4 tonometers in measuring postural IOP change.
Methods:
In healthy subjects, IOP was measured OU in with a Goldmann applanation tonometer (GAT) while sitting, then using the same GAT with the subject in the left lateral decubitus position after lying for 15 minutes, using a novel system comprising a motorized bed and modified slit-lamp table. On the next day, sitting IOP was measured in one eye using GAT, and in random order Tonopen XL and pneumatonometer. Then subjects lay down, and IOP was measured with these tonometers and also hand-held GAT (HA-2) after lying for 15 minutes and 45 minutes, supine except with GAT.
Results:
Enrolled were 19 subjects, 10 males and 9 females, with mean age 33.0±12.4 years. On day 1, sitting GAT IOP (mmHg) was 13.7±3.0 OD and 13.6±2.8 OS (p=0.7), and lying GAT IOP was 17.8±3.5 OD and 18.1±3.2 OS (p=0.3 for inter-eye postural IOP change). The coefficient of determination for right-left eye pairs of postural IOP difference was 0.453.On day 2, postural change after lying 15 minutes as measured with GAT, Tonopen, pneumatonometer, and HA-2 was 4.9±2.6, 1.6±1.8, 4.2±2.0 and 3.1±2.7, respectively. After lying 45 minutes it decreased to 3.3±2.1, 1.1±4.3, 3.1±2.5, and 2.6±3.3, respectively; this IOP decrease was statistically significant for GAT and pneumatonometer. In some subjects there was nearly no postural change in IOP, while in some IOP rose by 8-10 mmHg. 95% limits of agreement showed poor agreement between GAT and the other 3 tonometers in measured sitting and lying IOP and postural IOP change.
Conclusions:
Average postural IOP change was similar when measured with GAT and pneumatonometer, smaller with hand-held GAT, and much smaller with Tonopen. This change significantly decreased during lying between the 15 and 45 minute timepoints. Inter-subject variability in postural IOP was remarkable, consistent with previous reports, suggesting the importance of this parameter in clinical glaucoma practice. Inter-device agreement was poor and similar to previous reports.
Keywords: 568 intraocular pressure