Purpose

For years, ophthalmologists have been relying on clinic intraocular pressure (IOP) to manage glaucoma patients. There are studies which have shown that IOP can vary substantially throughout the day. This prospective observational study is to evaluate the relationship between the 24-hr mean IOP, peak IOP, trough IOP and clinic IOP and the timing of peak and trough IOP in glaucoma patients.

Methods

23 patients diagnosed with glaucoma were recruited and all of them were fitted with a contact lens sensor for 24 hours. The 24-hr mean IOP of each patient was recorded. The peak, trough and clinic IOP of each patient were recorded as well. The Pearson correlation coefficient between 24-hr mean IOP and peak IOP, trough IOP and clinic IOP were calculated and analysed. The circadian IOP pattern of glaucoma patients was constructed and analysed to determine the peak and trough.

Results

The Pearson correlation coefficient of 24-hr mean IOP and peak IOP among our subjects are r(23) = 0.8419 (p < 0.00001). The correlation coefficient between 24-hr mean IOP and trough IOP is r(23) = 0.8258 (p < 0.00001). However, the correlation coefficient between 24-hr mean IOP and clinic IOP is r(23) = 0.3608 (p = 0.091). The overall circadian IOP pattern showed peak IOP at 0730 and 1730 and showed trough IOP at 2130.

Conclusions

The 24-hr mean IOP showed significantly strong positive correlation with peak and trough IOP among glaucoma patients. However, the 24-hour mean IOP only showed weak positive correlation with the clinic IOP. We can possibly predict the 24-hour mean IOP in patients based on single peak or single trough IOP reading but measuring a single IOP in clinic might not tell us the 24-hour mean IOP of glaucoma patients. The best time to pick up peak or trough IOP to correlate with the 24-hour mean IOP is at 0730/1730 and 2130 respectively.