The current treatment options for open-angle glaucoma are primarily aimed at lowering intraocular pressure. The emergence of MIGS (minimally invasive glaucoma surgery) has revolutionized the management of glaucoma, and newer medical therapies have expanded the armamentarium for providers with improved safety and efficacy [5,6,7]. However, despite the emergence of new treatment options, these new options are imperfect and still carry risk. Currently, there are no treatment options that are non-laser, non-pharmacologic and non-invasive.
While intraocular pressure (IOP)-lowering strategies have been the mainstay of glaucoma treatment, a significant number of patients still progress despite a decrease in IOP following treatment . One possible explanation for this is that optic nerve damage occurs because of an imbalance between IOP and cerebrospinal fluid pressure (CSFp) posterior to the optic nerve. This is also known as the translaminar pressure difference (TLPD). When a person dives deep below sea level and experiences a significant increase in atmospheric pressure, this pressure acts on the entire body, including the CSFp and IOP, maintaining the TLPD. This explanation is supported by previous studies that suggest TLPD may play a significant role in the pathogenesis of glaucoma [8,9,10,11].
This present report evaluated the safety of a pair of goggles in the periorbital region attached to an intraocular pressure-adjusting pump, collectively known as the multi-pressure dial (MPD). The MPD establishes a microenvironment and produces a decrease in atmospheric pressure contacting the eye with the application of a negative pressure pump. This decrease in atmospheric pressure applied to the eye generates a corresponding instantaneous decrease in IOP. By lowering the pressure in the eye relative to other tissues in the body (e.g., blood pressure, CSFp) with the MPD, this may facilitate the decoupling of IOP from the CSFp. A graphic of this concept is shown in Fig. 3.
A poster presentation in 2019  demonstrated the IOP-lowering capabilities of the MPD at various negative pressure settings in healthy subjects. The results of this randomized, controlled study also showed that IOP reduction can be produced in a titratable fashion, even in normotensive eyes with the MPD. The MPD system evaluated in this study is similar to what was investigated in the aforementioned presentation.
The results of this study suggest that the MPD system is safe and tolerable for patients. No patients in this study endured any adverse events, and all patients were able to safely and comfortably wear the MPD for the duration of the study period. There were no observed post-study IOP spikes. The mean IOP values were actually lower 1 week after the study period in both the study and fellow (control) eye, and the difference was statistically significant. Although the modest IOP reduction observed at 1 week was statistically significant, it could be unrelated to treatment related to the device’s IOP-lowering ability and influenced by other factors such as IOP variability or diurnal variation.
This study is not without limitations. The sample size was small; controlled studies with longer duration and larger sample sizes would further elucidate the safety and efficacy of this device. Moreover, it is difficult to discern what negative effects, if any, the MPD may have over an extended treatment period. However, despite the limitations, we think the results of this preliminary study are meaningful and will promote further research of the device. Moreover, the initial results of this study are very promising; it was well tolerated by subjects, and the safety parameters used in this study demonstrated no indication that the MPD is not safe for use.
One potential limitation is that the vacuum pump or application of negative pressure by the MPD in the microenvironment could presumably dry out the ocular surface and trigger dry eye symptoms and possibly changes in TBUT values. However, in this study, all 30 patients had TBUT values unchanged from baseline in both the fellow and study eyes upon removal of the MPD as well as after 1 week. Moreover, there were no reports of dryness or irritation while wearing the device. Furthermore, none of the study subjects reported symptoms in the 7 days following wear of the MPD at their 1-week follow-up assessment. Given the tight seal of the MPD and the findings of this small study, it is possible the device may provide a secondary benefit of dry eye relief by acting as a moisture chamber, similar to what is performed in patients at risk of exposure keratopathy. However, further research would be valuable in exploring and validating this proposed benefit of dry eye relief.
At this point, it is unclear what, if any, effect the MPD’s negative atmospheric pressure application to the anterior orbital rim has on episcleral venous pressure or aqueous flow transversing the trabecular meshwork. This was a short-term study to evaluate preliminary safety and tolerability prior to undertaking longer term studies to further characterize the safety profile. Future studies investigating longer term wear may convey more insight on the MPD’s impact on factors proposed to contribute to the pathogenesis of glaucoma—episcleral venous pressure, trabecular meshwork resistance, etc.