Mean amplitude of intraocular pressure excursion a potential new factor for circadian IOP

The mean amplitude of intraocular pressure excursion (MAPE) appears to be a valuable parameter to describe circadian fluctuations in intraocular pressure (IOP) in glaucoma patients, a recent study has found.

In 164 patients with untreated primary open-angle glaucoma (POAG), the researchers monitored 24-h IOP with measurements every 2 hours, and fluctuations were expressed as MAPE. A non-contact tonometer was used for IOP measurements, and only from the right eye. Seventy-nine healthy controls were also included.

At baseline, IOP was higher in POAG patients, as was the vertical cup-disk ratio. Visual acuity, on the other hand, was significantly worse (p<0.001). Central corneal thickness was comparable between groups.

MAPE was significantly elevated among POAG patients relative to the healthy volunteers (4.16±1.90 vs 2.45±0.89; p<0.001). Another new parameter, called the area under circadian IOP curve (AUC_IOP), was similarly higher in POAG patients (379.40±96.42 vs 294.40±56.88; p<0.001).

Receiver operating characteristic (ROC) curve analysis was then performed to assess diagnostic efficiency of both MAPE and AUC_IOP, as well as traditional parameters such as the maximum difference of 24-h IOP and the mean and standard deviation (SD) of IOP.

MAPE ultimately came out on top, with an AUC of 0.822 (95 percent confidence interval [CI], 0.768–0.868). It was followed closely by the max difference, which had an AUC of 0.817 (95 percent CI,0.763–0.864). AUC_IOP achieved an AUC of 0.788 (95 percent CI, 0.731–0.838), while that for the mean and SD of IOP was 0.792 (95 percent CI, 0.735–0.841).

“[T]his study proposes a new parameter, MAPE, to characterize circadian IOP patterns in healthy people and untreated POAG patients. In untreated POAG patients, MAPE is more closely correlated with glaucoma severity than current IOP fluctuation parameters,” said researchers.