The effects of negative periocular pressure on intraocular pressure

Effects of Schlemm's Canal Suture Implantation Surgery and Pilocarpine Eye Drops on Trabecular Meshwork Pulsatile Motion

The trabecular meshwork is an important structure in the outflow pathway of aqueous humor, and its movement ability directly affects the resistance of aqueous humor outflow, thereby affecting the steady state of intraocular pressure (IOP). (1) Objective: The purpose of this study was to preliminarily estimate the effects of pilocarpine eye drops and trabeculotomy tunneling trabeculoplasty (3T) on trabecular meshwork (TM) pulsatile motion via phase-sensitive optical coherence tomography (Phs-OCT). (2) Method: In a prospective single-arm study, we mainly recruited patients with primary open-angle glaucoma who did not have a history of glaucoma surgery, and mainly excluded angle closure glaucoma and other diseases that may cause visual field damage. The maximum velocity (MV) and cumulative displacement (CDisp) of the TM were quantified via Phs-OCT. All subjects underwent Phs-OCT examinations before and after the use of pilocarpine eye drops. Then, all subjects received 3T surgery and examinations of IOP at baseline, 1 day, 1 week, 1 month, 3 months, and 6 months post-surgery. Phaco-OCT examinations were performed at 3 and 6 months post-surgery, and the measurements were compared and analyzed. (3) Results: The MV of TM before and after the use of pilocarpine eye drops was 21.32 ± 2.63 μm/s and 17.00 ± 2.43 μm/s. The CDisp of TM before and after the use of pilocarpine eye drops was 0.204 ± 0.034 μm and 0.184 ± 0.035 μm. After the use of pilocarpine eye drops, both the MV and CDisp significantly decreased compared to those before use (p < 0.001 and 0.013, respectively). The IOP decreased from baseline at 22.16 ± 5.23 mmHg to 15.85 ± 3.71 mmHg after 3 months post-surgery and from 16.33 ± 2.51 mmHg at 6 months post-surgery, showing statistically significant differences (p < 0.001). The use of glaucoma medication decreased from baseline at 3.63 ± 0.65 to 1.17 ± 1.75 at 3 months and 1.00 ± 1.51 at 6 months post-surgery; the differences were statistically significant (p < 0.001). Additionally, there was no statistically significant difference in the MV between 3 and 6 months after surgery compared to baseline (p = 0.404 and 0.139, respectively). Further, there was no statistically significant difference in the CDisp between 3 and 6 months after surgery compared to baseline (p = 0.560 and 0.576, respectively) (4) Conclusions: After the preliminary study, we found that pilocarpine eye drops can attenuate TM pulsatile motion, and that 3T surgery may reduce IOP without affecting the pulsatile motion status of the TM.

Negative Pressure Application via a Multi-Pressure Dial to Lower IOP in Patients with Suspected Glaucoma or Open Angle Glaucoma

PRCIS

The multi-pressure dial applies localized periocular negative pressure to safely and effectively lower IOP and represents the first non-invasive, non-pharmacologic device for IOP reduction.

OBJECTIVE

To evaluate the safety and effectiveness of the Multi-Pressure Dial (MPD) system, a device that applies periocular negative pressure to lower intraocular pressure (IOP).

SETTING

6 investigational sites, United States.

DESIGN

Prospective, assessor-masked, randomized controlled trial.

METHODS

Subjects with suspected glaucoma, ocular hypertension (OHTN), and open angle glaucoma (OAG) with baseline IOP ≥13 mmHg and ≤32 mmHg were enrolled. One eye of each subject was randomized to receive negative pressure application; the fellow eye served as a control. The study eye negative pressure setting was programmed for 60% of the baseline IOP. The primary effectiveness endpoint was the proportion of study eyes versus control eyes achieving an IOP reduction ≥20% at Day 90. Secondary endpoints included the proportion of eyes achieving an IOP reduction ≥25% at Day 90 as well as the proportion of eyes achieving an IOP reduction ≥20% at Days 30 and 60.

RESULTS

116 eyes of 58 subjects completed the study. At the Day 90 visit, 89.7% ( n =52) of study eyes versus 3.4% ( n =2) of control eyes achieved an IOP reduction ≥20% ( P <0.001). At Day 90, 77.6% ( n =45) of study eyes achieved a ≥25% IOP reduction compared to 1.7% ( n =1) of control eyes ( P <0.001). The most commonly reported adverse events were lid (17.2% study eye, 7.8% control eye) and periorbital edema (14.1% study eye, 10.9% control eye).

CONCLUSIONS

This trial demonstrates that the MPD safely and effectively lowers IOP in a group of patients that included glaucoma suspects, OHTN, and patients with OAG.

The Effects of Negative Periocular Pressure on Biomechanics of the Optic Nerve Head and Cornea: A Computational Modeling Study

Purpose

The purpose of this study was to evaluate the effects of negative periocular pressure (NPP), and concomitant intraocular pressure (IOP) lowering, on the biomechanics of the optic nerve head (ONH) and cornea.

Methods

We developed a validated finite element (FE) model of the eye to compute tissue biomechanical strains induced in response to NPP delivered using the Multi-Pressure Dial (MPD) system. The model was informed by clinical measurements of IOP lowering and was based on published tissue properties. We also conducted sensitivity analyses by changing pressure loads and tissue properties.

Results

Application of -7.9 mmHg NPP decreased strain magnitudes in the ONH by c. 50% whereas increasing corneal strain magnitudes by c. 25%. Comparatively, a similar increase in corneal strain was predicted to occur due to an increase in IOP of 4 mmHg. Sensitivity studies indicated that NPP lowers strain in the ONH by reducing IOP and that these effects persisted over a range of tissue stiffnesses and spatial distributions of NPP.

Conclusions

NPP is predicted to considerably decrease ONH strain magnitudes. It also increases corneal strain but to an extent expected to be clinically insignificant. Thus, using NPP to lower IOP and hence decrease ONH mechanical strain is likely biomechanically beneficial for patients with glaucoma.

Translational Relevance

This study provides the first description of how NPP affects ONH biomechanics and explains the underlying mechanism of ONH strain reduction. It complements current empirical knowledge about the MPD system and guides future studies of NPP as a treatment for glaucoma.

Multipressure Dial Goggle Effects on Circumpapillary Structure and Microvasculature in Glaucoma Patients

PURPOSE

To evaluate the effects of pressure changes induced by a multipressure dial (MPD) on circumpapillary retinal nerve fiber layer (RNFL) and capillary density (CD) measurements in patients with glaucoma using OCT angiography (OCTA).

DESIGN

Prospective interventional study.

PARTICIPANTS

Twenty-four patients with primary open-angle glaucoma.

METHODS

One eye of each patient underwent negative pressure application with the MPD. The MPD alters intraocular pressure (IOP) relative to atmospheric pressure by generating a negative pressure vacuum within a goggle chamber that is placed over the eye. Each participant underwent serial high density OCTA imaging (AngioVue) of the optic nerve head at different negative pressure increments of -5 mmHg, starting from 0 mmHg, ending at -20 mmHg, and then returning to baseline. Images were acquired after 2 minutes of sustained negative pressure at each target pressure to allow for stabilization of the retinal structures and microvasculature. The RNFL thickness and CD measurements were automatically calculated using the native AngioVue software, and then exported for analysis.

MAIN OUTCOME MEASURES

The influence of different levels of negative pressure on circumpapillary RNFL thickness and CD measurements, assessed by a linear mixed-effects model with repeated measures.

RESULTS

The mean (± SD) age was 71.0 years (± 7.8 years), the baseline IOP was 17.5 mmHg (± 3.6 mmHg), and there was a mean 24-2 mean deviation of -2.80 dB (± 2.55 dB). Serial circumpapillary CD measurements showed a statistically significant dose-dependent increase from baseline, without negative pressure application, to the maximum negative pressure application of -20 mmHg (difference, 2.27%; P = 0.010). Capillary density measurements then decreased symmetrically when lowering the negative pressure to baseline. Circumpapillary CD measurements at target negative pressures of -10 mmHg, -15 mmHg, and -20 mmHg were significantly higher than the baseline measurements (all P values < 0.05). Circumpapillary RNFL thickness remained the same throughout different levels of negative pressure.

CONCLUSIONS

Circumpapillary CD measurements showed a dose-dependent increase with the induction of negative pressure, while RNFL thickness measurements remained unchanged.

Structural and Metabolic Imaging After Short-term Use of the Balance Goggles System in Glaucoma Patients: A Pilot Study

PRCIS

Short-term use of the Balance Goggles System (BGS) in glaucoma patients was not associated with the observable changes in conventional ocular coherence tomography (OCT) imaging, but metabolic imaging using peripapillary flavoprotein fluorescence (FPF) may represent a useful adjuctive investigation.

OBJECTIVE

To determine whether the intraocular pressure (IOP)-lowering effects of the BGS are accompanied by changes in retinal thickness measured by OCT, retinal vascular density measured by ocular coherence tomography-angiography (OCTA), or novel peripapillary metabolic profiling using FPF measured by a fundus camera.

DESIGN

Prospective comparative case-series.

SUBJECTS

Eight eyes from 8 patients with open angle glaucoma ranging from mild to severe.

METHODS

In this prospective, single-center, open-label, nonrandomized, and single-arm study patients received a baseline evaluation including retinal imaging, then 1 hour of negative pressure application through the BGS, followed by repeat retinal imaging. Participants then used the BGS at home for 1 month and underwent a repeat evaluation at the conclusion of the trial.

MAIN OUTCOME MEASURES

Changes in nerve fiber layer thickness, OCTA vascular parameters, and FPF scores.

RESULTS

Mean baseline IOP was 18.0±3.1 mmHg and there was no significant change in IOP at follow-up. At 1 month compared with baseline, there was a statistically significant improvement in FPF optic nerve head rim scores (12.7±11.6 to 10.5±7.5; P =0.04). In addition, there was a trend toward an increase in retinal nerve fiber layer thickness after 1 month (69.5±14.2 to 72.0±13.7; P =0.1), but there were no statistically significant differences observable with any of the OCTA vascular parameters either at 1 hour or after 1 month.

CONCLUSIONS

There were no significant changes observable using conventional OCT imaging after short-term use of the BGS, although metabolic imaging using FPF may be a useful potential biomarker to complement existing investigations. Additional studies are warranted to further investigate these changes.

Intraocular Pressure Measurement with Pneumatonometry and a Tonometer Tip Cover During Negative Pressure Application

Purpose

This is a 2-part study to investigate the agreement between pneumatonometry and direct pressure transducer intraocular pressure (IOP) measurements in a perfusion organ culture (POC) model where (1) the perfusion fluid column is open to atmospheric pressure, holding IOP constant to permit evaluation of the impact of negative pressure (NP) on IOP measurements, and (2) the perfusion fluid column is a closed system, allowing IOP to vary with NP application.

Methods

The first part incorporated a fluid column open to atmospheric pressure, maintaining IOP constant to permit evaluation of the effect of applied NP on IOP measurement accuracy. In the second part, the POC column was closed, allowing IOP to vary with NP application and permit evaluation of agreement between pneumatonometry and pressure transducer measurements. In each part, four perfused tissues were used in thirteen paired pre-set IOP (10, 20, 25, 30 mmHg) and NP (0, 5, 10, 15, 20 mmHg) combinations, resulting in a total of 1040 paired measurements (520 per study). The difference in IOP measurements (Δ IOP = Excursion tonometry – pressure transducer) was calculated at each paired configuration.

Results

During the first part, the mean Δ IOP was −0.7 ± 1.6 mmHg across all measurements. During the second part, the mean Δ IOP across all measurements was +0.7 ± 1.4 mmHg. At NP settings of −5, −10, −15, and −20 mmHg, across all pre-set IOPs, the mean IOP reduction via Excursion tonometry was 3.1 ± 0.3, 5.6 ± 1.3, 8.5 ± 1.7 and 11.2 ± 1.8 mmHg, respectively.

Conclusion

Measurement of IOP via Excursion tonometry yields results within the accuracy range of the pneumatonometry device (per manufacturer) and is minimally impacted by NP application. The IOP-lowering results are consistent with previous studies and further support the effectiveness of the Multi-Pressure Dial in lowering IOP relative to atmospheric pressure.

The Effect of Periocular Negative Pressure Application on Intraocular and Retrobulbar Pressure in Human Cadaver Eyes

Introduction

To investigate the effect of applying negative pressure (vacuum) to the periocular space on intraocular pressure (IOP) and retrobulbar pressure (RBP) by use of the Multi-Pressure Dial (MPD) system (Equinox Ophthalmic, Inc.).

Methods

Two eyes of two full body cadavers were studied. In each subject, the retrobulbar space, posterior segment and intra-goggle space were cannulated to provide direct IOP, RBP and intra-goggle pressure measurements via a pressure transducer data acquisition system. The goggles of the MPD system were placed over the eyes of each subject, and multiple test runs were performed, with negative pressure settings programmed to 5, 10 and 20 mmHg. IOP and RBP measurements were continuously obtained during each run and plotted against time for analysis.

Results

For both subjects, the mean reduction (± standard deviation) in IOP was 1.6 ± 0.9 (10%), 3.5 ± 1.8 (23%) and 5.6 ± 2.0 (37%) mmHg at programmed negative pressure levels of − 5, − 10 and − 20 mmHg, respectively. The overall mean change in RBP (mmHg) during negative pressure application was 0.02 ± 0.14 at − 5 mmHg, 0.03 ± 0.19 at − 10 mmHg and − 0.01 ± 0.18 at − 20 mmHg. In both subjects, the magnitude of RBP change during application of negative pressure fell below the uncertainty of the measurement system.

Conclusions

The application of negative pressure to the periocular space with the MPD decreases IOP but does not affect RBP.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40123-021-00442-2.

In-Vivo Measurement of Ocular Deformation in Response to Ambient Pressure Modulation

A novel approach is presented for the non-invasive quantification of axial displacement and strain in corneal and anterior crystalline lens tissue in response to a homogenous ambient pressure change. A spectral domain optical coherence tomography (OCT) system was combined with a custom-built set of swimming goggles and a pressure control unit to acquire repetitive cross-sectional scans of the anterior ocular segment before, during and after ambient pressure modulation. The potential of the technique is demonstrated in vivo in a healthy human subject. The quantification of the dynamic deformation response, consisting of axial displacement and strain, demonstrated an initial retraction of the eye globe (−0.43 to −1.22 nm) and a subsequent forward motion (1.99 nm) in response to the pressure change, which went along with a compressive strain induced in the anterior crystalline lens (−0.009) and a tensile strain induced in the cornea (0.014). These mechanical responses appear to be the result of a combination of whole eye motion and eye globe expansion. The latter simulates a close-to-physiologic variation of the intraocular pressure and makes the detected mechanical responses potentially relevant for clinical follow-up and pre-surgical screening. The presented measurements are a proof-of-concept that non-contact low-amplitude ambient pressure modulation induces tissue displacement and strain that is detectable in vivo with OCT. To take full advantage of the high spatial resolution this imaging technique could offer, further software and hardware optimization will be necessary to overcome the current limitation of involuntary eye motions.

Posterior ocular structural changes and glaucoma susceptibility in patients with hemifacial spasm

PURPOSE

To evaluate the changes in the posterior ocular structures and glaucoma susceptibility in patients with hemifacial spasm (HFS).

STUDY DESIGN

Prospective observational clinical study.

METHODS

This study included 46 long-standing HFS patients with a minimum follow-up of 12 months. The participants' eyes were divided into three groups: (1) 46 affected eyes of patients with clinical HFS; (2) 46 unaffected fellow eyes and, (3) 46 eyes of healthy sex and age-matched controls. All participants were assessed by a detailed clinical examination and optical coherence tomography (OCT) with enhanced depth imaging (EDI). EDI-OCT images were binarized using ImageJ software. Peripapillary retinal nerve fiber layer (RNFL), ganglion cell complex (GCC), choroidal thickness (CT), and choroidal vascularity index (CVI) were used to compare the structural characteristics of the affected eyes with fellow and control eyes. The CT measurements were performed from the subfoveal and locations at 750 μm and 3000 μm intervals from the foveal center, and the average of CT measurements at 5 locations was accepted as mean CT.

RESULTS

The demographic and clinical characteristics among the groups were similar (for all, P > 0.05). Mean peripapillary RNFL thickness of the inferior quarter was significantly lower in affected eyes, compared to fellow eyes (P = 0.023) and control eyes (P = 0.040). Mean GCC thickness significantly decreased in affected eyes, compared to fellow eyes (P = 0.019) and healthy controls (P = 0.008). Mean CT thickness significantly decreased in affected eyes, compared to fellow eyes (P = 0.002) and healthy controls (P < 0.001). Mean subfoveal CVI (65.94% ± 1.46) was found to be significantly thinner than the unaffected fellow (68.19% ± 1.84, P = 0.011) eyes and control eyes (67.23% ± 0.84, P = 0.044).

CONCLUSIONS

This study's outcomes show that long-standing HFS is associated with glaucoma-associated morphological OCT findings and decreased both CT and subfoveal choroidal vascularity. These findings may be related to the fact that the posterior ocular structures are affected by long-lasting paroxysmal orbicularis contractions.

Evaluation of the IOP-Lowering Effect of a Multi-Pressure Dial at Different Negative Pressure Settings

Purpose

To evaluate the intraocular pressure (IOP)-lowering effect of a multi-pressure dial (MPD) at targeted negative pressure settings.

Methods

Prospective, intrasubject controlled study of 65 healthy subjects randomized to receive no negative pressure for 60 minutes or negative pressure application at designated levels of 25%, 50%, and 75% of baseline IOP for 20 minutes each. The main outcome measure was mean IOP with application of negative pressure.

Results

In the study eye group, from a baseline IOP of 15.8 ± 3.6 mm Hg, the mean IOP was 13.5 ± 3.4, 11.5 ± 3.1, and 10.2 ± 2.7 mm Hg with negative pressure settings of 25%, 50% and 75%, respectively. In the control eye group, from a baseline IOP of 15.5 ± 3.0 mm Hg, the mean IOP values at the same time points, without negative pressure, were 15.6 ± 3.0, 15.5 ± 2.5 and 15.3 ± 2.4 mm Hg. The difference between the mean IOPs of the two groups was significantly different at all negative pressure settings (P < 0.001) in comparison with baseline. There was one minor adverse event, a corneal abrasion, that was unrelated to device wear.

Conclusions

Negative pressure application to the periocular space with a multi-pressure dial can produce titratable IOP reduction while the device is worn with active negative pressure. To our knowledge, this technology represents the first nonpharmacologic, nonlaser, nonsurgical method for IOP reduction.

Translational Relevance

This represents the first study demonstrating the IOP-lowering ability of the multi-pressure dial, a device that uses a novel IOP-lowering strategy by delivering negative pressure to the periocular region.

Overnight Safety Evaluation of a Multi-Pressure Dial in Eyes with Glaucoma: Prospective, Open-Label, Randomized Study

Purpose

To investigate the safety and tolerability of the multi-pressure dial (MPD) worn overnight for seven consecutive days.

Design

Prospective, open-label, randomized, single-site study.

Subjects

Twenty eyes of 10 subjects with open-angle glaucoma were fitted with an MPD and randomized to negative pressure application of −10 mmHg in one eye (study eye) worn overnight for 7 consecutive days.

Methods

Safety measures included best-corrected visual acuity (BCVA), intraocular pressure (IOP) changes from baseline during and after negative pressure application, slit lamp and dilated fundus exam findings, and rate of adverse events. Subjective assessments were completed daily by the subjects during the 7-day study period and immediately following the study period.

Results

Prior to the 7-day testing period, application of 10 mmHg negative pressure reduced mean IOP from 18.2 ± 3.8 mmHg to 14.0 ± 2.1 mmHg (p<0.01), a 22% reduction. After 7 days of consecutive nightly wear, repeat IOP measurements with the application of negative pressure showed a decrease in mean IOP from 16.9 ± 4.3 mmHg to 13.5 ± 3.7 mmHg. The observed IOP reduction was in addition to the subjects’ current treatment regimen. There were no statistically significant changes in IOP, BCVA from baseline following the 7-day period of nightly wear with the application of negative pressure. The patient-reported outcomes were favorable.

Conclusion

The MPD can safely and comfortably be worn overnight. The decrease in IOP of >20% in addition to current therapy is both clinically and statistically significant. The MPD shows promise as a potential new treatment option for nocturnal IOP control.

Short-Term Steady-State Pattern Electroretinography Changes Using a Multi-Pressure Dial in Ocular Hypertensive, Glaucoma Suspect, and Mild Open-Angle Glaucoma Patients: A Randomized, Controlled, Prospective, Pilot Study

Introduction

This study evaluates the effects of the multi-pressure dial (MPD) on steady-state pattern electroretinography (ss-pERG) parameters. The study is a randomized, controlled, prospective, pilot trial in a private practice setting with ocular hypertensive (OHT), glaucoma suspect, and open-angle glaucoma (OAG) subjects.

Methods

This study included nine patients (64 ± 9.0 years, nine female) with OHT, glaucoma suspect, or mild OAG. One eye of each subject was randomized to receive negative periocular pressure, while the contralateral eye served as the intrasubject control through the goggle without negative pressure. The Diopsys High Contrast Sensitivity ss-pERG protocol was conducted on both eyes of each subject while wearing the MPD device. Application of negative periocular pressure was set at 50% of baseline intraocular pressure for each study eye.

Results

Following 2 h of negative periocular pressure application, the difference in MagnitudeD (MagD) from baseline for eyes randomized to receive negative periocular pressure (+ 0.17 versus  − 0.26) was statistically significant (p = 0.023). Over the same period, the change in MagD/Magnitude (MagD/Mag ratio) from baseline for eyes randomized to receive negative periocular pressure was also higher (+ 0.14 versus  − 0.16), compared to the control eyes, approached significance (p = 0.059).

Conclusions

Following 2 h of MPD wear, the measured MagD and MagD/Mag ratio improved compared to control, suggesting that negative periocular pressure application to the anterior globe can lead to short-term improvement in one measure of retinal ganglion cell function.

Evaluation of negative pressure transfer through tissue in a benchtop cornea and eyelid model

PURPOSE

A new glaucoma treatment device, known as the multi-pressure dial (MPD), has been introduced, which offers a novel approach to IOP reduction by delivering negative pressure to the periocular region. Clinical studies have demonstrated the IOP-lowering effect of the MPD via direct measurements using pneumatonometry. It remains unclear whether the eyelids, when closed, affect the transmission of negative pressure and subsequently affect IOP reduction. This study aimed to evaluate whether the transfer of negative pressure and subsequent decrease in IOP are altered by the presence of synthetic eyelid tissue.

METHODS

A model with 13 different configurations controlling for eyelid material type, presence of slit/opening, and eyelid-cornea contact was employed. The slit modification was employed to mimic the physiologic separation that exists between the eyelids. Baseline IOP within an eye model was set at various levels ranging from 10 to 30 mmHg with applied negative pressure settings of 10, 15, and 20 mmHg utilized at each baseline IOP. The percentage of vacuum transfer was calculated by comparing baseline IOP to resultant IOP measurements following application of vacuum to the system.

RESULTS

In the open configuration (without eyelid tissue), the mean % vacuum transfer was 98.7%. The sealed, full-contact configurations exhibited values of 97.4%, 98.8%, and 97.2%. The slit configurations, which closely mimic the physiologic eyelid, demonstrated a mean % vacuum transfer of 98.7% across all settings.

CONCLUSIONS

The impact of eyelid tissue on transfer of negative pressure can be isolated and evaluated. The presence of eyelid tissue has an insignificant impact on the transfer of negative pressure, and the IOP reduction achievable with the MPD would not be altered with the eyelids closed.