This is a relevant study that reports results obtained with a relatively new technology (Contact lens Sensor; CLS) on IOP related fluctuations during 24 hours, in a sample of medically and surgically treated glaucoma patients. IOP-related fluctuations were larger in the medically treated group, and a larger fraction of the surgical group exhibited an absence of nocturnal acrophase when compared to the medically treated group.
Similarly, Konstas and associates1 evidenced that glaucoma patients with well-functioning trabeculectomies had lower mean IOP, but also lower peaks and ranges of IOP over 24 hours when compared with glaucoma patients on maximum tolerated medical therapy.
Furthermore, we have also demonstrated that trabeculectomy is able to reduce but not to avoid IOP elevation due to changing posture from sitting to supine position.2
Some considerations should be done either about technology, and the significance of nighttime fluctuations. CLS have been demonstrated to have a good correlation with 24 IOP fluctuation profile in glaucoma patients.3
In the study of Muniesa and associates there was a significant difference in IOP levels between the two groups, nevertheless after adjustment for IOP as measured by applanation tonometry, surgical patients had less IOP related fluctuations in 24-hours than the medical group. In order to better analyze the results, it would be interesting to know if there were any difference in 24-hour blood pressure profile between the studied groups. Pulsatile ocular blood flow, the volume of blood entering the eye for each cardiac cycle, is part of IOP related fluctuations, and thus CLS measurements could reflects modifications of ocular perfusion pressure. For this reason, it should be interesting to analyze the results also after adjusting for blood pressure, and possibly for blood pressure medicines between the two groups.
The role of nighttime IOP fluctuations in glaucoma progression is not completely understood and investigated
It is important to consider that the role of nighttime IOP fluctuations in glaucoma progression is not completely understood and investigated, even if it is logical to believe that stable and low 24-hours IOP is a desirable target for glaucoma patients. More convincing literature exists that correlates progression of glaucoma in patients with larger 24-hours fluctuation of ocular perfusion pressure.4 For this reason, it is possible to speculate that the use of CLS associated with 24-hour blood pressure assessment should be an integrated method to evaluate the risk of progression of the disease.
I applaud the authors for their effort making a substantial contribution to glaucoma research.