Abstract
Purpose: :
To determine if a diurnal IOP rhythm exists and is consistent from day to day
Methods: :
16 normal subjects prospectively underwent Goldmann IOP measurements at 8AM, 10AM, 12PM, 2PM and 4PM, on two separate days one week apart. A mean of 2 measurements at each time point was used to calculate (for each eye) the IOP change between each time point, defined as the IOP at the earlier time minus the IOP at the later time, for each time interval: 8–to–10, 10–to–12, 12–to–2, and 2–to–4. This measure captured both magnitude and direction of IOP change between each pair of time points. Linear regression was used to correlate each eye's IOP change for each time interval at visit 1 versus visit 2. (In the regression, the IOP change in each eye over each time interval at the first visit was plotted against the IOP change in the same eye over the same time interval at the second visit one week later; each patient contributed 8 data points, one from each eye at each time interval.)
Results: :
No correlation was observed for the magnitude and direction of IOP change within eyes during corresponding time points on two days one week apart (r2 = 0.0002). Examining right and left eyes separately yielded identical results (r2 = 0.0066 and 0.0184, respectively).
Conclusions: :
The pattern of IOP fluctuation in normal eyes on a given day is independent of the same eye's IOP fluctuation pattern one week later, suggesting that a conserved diurnal IOP rhythm does not exist.
Keywords: intraocular pressure • circadian rhythms