Intraocular pressure circadian rhythm in stable and advanced primary open-angle glaucoma
Aim. To study the features of the daily dynamics and parameters of the intraocular pressure circadian rhythm (IOP CR) in patients with stable and progressive (advanced) primary open-angle glaucoma (S-POAG / P-POAG) in comparison with the results of age and sex age-matched peers (Control). Material and methods. IOP CR parameters were studied in the three groups: S-POAG, (n = 65, mean age 67.6 ± 7.6); P-POAG (n = 50, 69.9 ± 8.2); and Controls: patients without glaucoma (n = 89, 68.1 ± 10.6). Self-measurements of IOP were obtained for the 3 consecutive days (72 hours) at 3, 8, 11, 14, 17, 20, 23 hours. Results revealed the distinctive features of CR IOP in S-POAG and P-POAG patients: in S-POAG, similarly to the control group, the peak value was achieved mainly during morning hours (08-11 hours) with nocturnal nadir at 3:00; whereas the patients of the P-POAG group had a diametrically opposite pattern. Despite the increase in amplitude, CR IOP in both POAG groups is characterized by a marked decrease in percent rhythm. In addition, there is a gradual trend in the internal phase lag between the IOP CR and the «marker» CR of body temperature between the three groups. Conclusions. Distinctively different circadian patterns of IOP in S-POAG and P-POAG groups, progressive increase of the chaotic component of IOP variability associated with a decrease in 24-hour percentage rhythm in POAG groups (a manifestation of hyper-variable extra-circadian dissemination) and the gradual phase shift between IOP and body temperature circadian rhythms, serve as manifestations of the internal desynchronization. The value of the global retinal ganglion cell loss index (global loss volume) of 10-15% as gauged by optical coherence tomography may define a threshold for IOP circadian rhythm phase misalignment.