Positive and Negative Pressure Goggles for Eye Diseases

Key Points at a Glance

Key Points of This Disease

• Positive-pressure and negative-pressure goggles are investigational devices that noninvasively alter intraocular pressure by applying pressure around the orbit.
• Negative-pressure goggles (NPG) lower intraocular pressure, while positive-pressure goggles raise it, thereby adjusting the pressure gradient across the lamina cribrosa.
• Research is being conducted on applications for diseases involving pressure imbalance at the lamina cribrosa, such as glaucoma, idiopathic intracranial hypertension, and SANS.
• Clinical studies using Equinox’s negative pressure goggles (Multi-Pressure Dial) have confirmed good safety and intraocular pressure-lowering effects.
• Spontaneous venous pulsation (SVP) is attracting attention as a potential biomarker reflecting changes in intraocular and intracranial pressure.
• Currently, these devices are still in the research stage and cannot be prescribed or used in general clinical practice.
• Standard treatments for idiopathic intracranial hypertension include acetazolamide and cerebrospinal fluid shunting; pressure goggles are not a substitute for these.

1. What are positive and negative pressure goggles for eye diseases?

Pressure goggles are devices that noninvasively adjust intraocular pressure (IOP) by applying negative or positive pressure around the orbit.

• Negative pressure goggles (NPG): Use vacuum to lower pressure within the orbit, thereby reducing IOP.
• Positive pressure goggles: Apply positive pressure around the orbit to increase IOP, potentially normalizing the translaminar pressure gradient in conditions of elevated intracranial pressure (ICP).

The following three disease groups are being studied as potential applications:

• Glaucoma: Characterized by progressive loss of retinal ganglion cells (RGCs), with the lamina cribrosa considered the primary site of RGC axon damage. Reports indicate that 25–50% of glaucoma patients in the United States have IOP within the “normal” range, drawing attention to factors other than IOP, such as the translaminar pressure gradient.
• Idiopathic intracranial hypertension (IIH): A neuro-ophthalmic disorder characterized by elevated intracranial pressure and papilledema. Major risk factors include female sex and obesity. ¹⁾
• Spaceflight-Associated Neuro-ocular Syndrome (SANS): A group of neuro-ophthalmic findings observed after long-duration spaceflight, including optic disc edema, globe flattening, hyperopic shift, and choroidal folds.

Currently, this is in the research and development stage and is not a standard treatment widely used in clinical practice.

Q What is the mechanism of a pressure goggle device?

A

Negative pressure goggles lower intraocular pressure by creating a vacuum (negative pressure) around the orbit, while positive pressure goggles raise intraocular pressure by applying positive pressure. These mechanisms aim to adjust the pressure difference between intraocular pressure and intracranial pressure across the optic nerve head (lamina cribrosa). Both are currently research-stage devices and are not available for general clinical use.

2. Main Symptoms and Clinical Findings

The common symptoms and findings of the disease groups targeted by pressure goggles are shown below.

Subjective Symptoms

Glaucoma-related:

• Visual field defect: Progressively enlarges. Often asymptomatic in the early stages.

Idiopathic intracranial hypertension-related: ¹⁾

• Headache: Often worsens upon waking.
• Transient visual obscurations: Episodes of vision loss lasting seconds to minutes, triggered by postural changes or coughing.
• Diplopia: Horizontal diplopia due to abducens nerve (cranial nerve VI) palsy.
• Pulsatile tinnitus: Tinnitus synchronized with the heartbeat.
• Visual loss: Severe papilledema can lead to irreversible visual impairment.

Related to low intracranial pressure:

• Orthostatic headache: Headache that appears or worsens upon standing.
• Dizziness, neck pain, vomiting, horizontal diplopia

Clinical Findings

Glaucoma

Optic disc cupping: Enlargement of the central cup (cupping) of the optic disc is a characteristic finding.

Visual field defects: Patterns such as arcuate scotoma and nasal step on Humphrey visual field testing.

Idiopathic Intracranial Hypertension

Papilledema: Bilateral involvement is characteristic. Assessed using the Frisén classification. ¹⁾

RNFL thickening: OCT shows marked retinal nerve fiber layer thickening. ¹⁾

Visual field abnormalities: Enlargement of the Mariotte blind spot and generalized visual field depression. ¹⁾

Abducens nerve palsy: False localizing sign due to increased intracranial pressure. ¹⁾

SANS

Optic disc edema: Appears after long-duration spaceflight.

Globe flattening: Flattening of the posterior pole.

Hyperopic refractive shift: Caused by changes in spherical aberration.

Choroidal folds: Observed in the posterior pole.

3. Causes and Risk Factors

The core pathology targeted by pressure-lowering goggles is an abnormality in the translaminar pressure gradient.

• Mechanical position of the lamina cribrosa: The lamina cribrosa is a structure sandwiched between two pressures: intracranial pressure (ICP) from the front and intraocular pressure (IOP) from the back. This pressure difference is the “translaminar pressure gradient,” and evidence is accumulating that an imbalance between IOP and ICP contributes to optic nerve damage.
• Pressure gradient in glaucoma: When IOP significantly exceeds ICP, the lamina cribrosa is displaced posteriorly, which is thought to damage RGC axons.
• Pressure gradient in idiopathic intracranial hypertension: When ICP greatly exceeds intraocular pressure, the lamina cribrosa is displaced anteriorly, causing papilledema. ¹⁾
• Risk factors for idiopathic intracranial hypertension: Female sex and obesity are the main risk factors. ¹⁾
• Diurnal variation of intraocular pressure: Intraocular pressure shows a diurnal variation pattern, peaking at night. As intraocular pressure rises, ocular perfusion pressure (OPP) decreases.
• Pathophysiological hypotheses of SANS: Cephalad fluid shift, increased ICP, ocular glymphatic stasis, and pulsatile changes in brain volume are proposed etiological hypotheses.

Spontaneous venous pulsation (SVP) and biomarkers of pressure gradient:

• SVP is the pulsation of the central retinal vein, with a prevalence of 87.6–98% in healthy eyes.
• The prevalence of SVP is reduced in patients with glaucoma and IIH.
• Venous pulsation pressure (VPP) tends to be higher in glaucoma patients and may serve as an indicator of disease progression.
• SVP and VPP may be usable as biomarkers for IIH, glaucoma, and SANS.

Guidelines for Seeking an Eye Exam

Glaucoma often has no noticeable symptoms, so regular eye pressure tests and visual field tests are important. If you have symptoms of idiopathic intracranial hypertension (persistent headache, transient vision loss, double vision, pulsatile tinnitus), promptly see an ophthalmologist or neurologist.

Q Why is the "balance" between intraocular pressure and intracranial pressure important?

A

The lamina cribrosa is sandwiched between two pressures: intraocular pressure (from behind) and intracranial pressure (from the front). This pressure difference (translaminar pressure gradient) places physical stress on the optic nerve. The greater the pressure difference, the more the lamina cribrosa deforms, making the optic nerve fibers more susceptible to damage. Glaucoma, idiopathic intracranial hypertension, and SANS are all thought to involve abnormalities in this pressure balance as part of their pathology.

4. Diagnosis and Examination Methods

The main evaluation methods related to the research and use of pressurized goggles are shown below.

• Intraocular pressure measurement: A basic indicator for evaluating the effect of goggles. It has been confirmed that accurate intraocular pressure measurement is possible with pneumatonometry using a Tono-Pen tip cover even under NPG wear (Ferguson et al. study).
• Excursion test method: A measurement method combining a Tono-Pen tip cover and NPG. A technique that collected 480 pairs of measurements at four pressure levels (7, 10, 20, 30 mmHg) and confirmed reproducibility.
• Visual field test (Humphrey perimetry): Used to evaluate the progression of target diseases (glaucoma, idiopathic intracranial hypertension). ¹⁾
• OCT (Optical Coherence Tomography): Measurement of peripapillary retinal nerve fiber layer (pRNFL) thickness. Useful for quantitative assessment of papilledema. ¹⁾
• SVP/VPP measurement: Observable with ophthalmoscopy. Evaluation of SVP during pressure changes may allow indirect measurement of ICP using goggles.

5. Standard Treatment

Pressure goggles are investigational devices and are not currently standard treatment. Current standard treatments for each target disease are shown below.

Current Standard Treatment for Glaucoma

• Medication (eye drops): Lowering intraocular pressure is the only proven treatment. However, it can be unpredictable and efficacy may be compromised by poor adherence.
• Laser therapy (SLT, etc.): Selective laser trabeculoplasty.
• Surgery (trabeculectomy, tube shunt, etc.): Chosen when medication and laser therapy are insufficient.

Current Standard Treatment for Idiopathic Intracranial Hypertension

• Acetazolamide: Offered as first-line treatment for many patients. ¹⁾ Emergency management is required in cases with vision threat.
• Optic nerve sheath fenestration (ONSF): Effective for treating papilledema but does not lower ICP. Not recommended for headache treatment. Complications include diplopia, anisocoria, and tonic pupil. ¹⁾
• Cerebrospinal fluid shunt surgery: Ventriculoperitoneal (VP) shunt and lumboperitoneal shunt. Effectively lowers ICP and improves optic disc edema and headache (short-term effect). Complications include shunt malfunction, infection, and malposition. ¹⁾
• Emergency management of fulminant idiopathic intracranial hypertension: A combination of lumbar drainage placement, acetazolamide (starting at 500 mg three times daily and increasing to 3–4 g/day), and IV methylprednisolone (1 g/day for 3 days) may be used. However, steroids are not recommended for non-fulminant idiopathic intracranial hypertension. ¹⁾

Note on pressure goggles

Pressure goggles are currently investigational devices and are not standard treatment prescribed or used in clinical practice. Treatment for glaucoma and idiopathic intracranial hypertension should be performed under the management of an ophthalmologist or neuro-ophthalmologist.

6. Pathophysiology and detailed mechanisms

Lamina cribrosa biomechanics

The lamina cribrosa is a structure sandwiched between two pressures: intraocular pressure (from behind) and intracranial pressure (from in front).

• Glaucoma: Intraocular pressure greatly exceeds ICP → posterior displacement of the lamina cribrosa → mechanical damage to RGC axons. It has been hypothesized that periodically adjusting the pressure gradient across the lamina cribrosa may protect the optic nerve and slow glaucoma progression.
• Idiopathic intracranial hypertension: ICP greatly exceeds intraocular pressure → anterior displacement of the lamina cribrosa → formation of papilledema. ¹⁾

Mechanism of action of pressurized goggles

• Effect of negative-pressure goggles: Applying -10 mmHg pressure to the orbit can lower intraocular pressure by about 6 mmHg without affecting ICP. This may improve the lamina cribrosa pressure gradient in glaucoma.
• Effect of positive-pressure goggles: Raising intraocular pressure may normalize the pressure gradient across the lamina cribrosa during ICP elevation. This is primarily considered for application in SANS.

Physical basis of spontaneous venous pulsation (SVP)

The occurrence of SVP is due to the mechanism: cardiac cycle → cerebrospinal fluid pulsation → oscillation of transmural pressure. The visibility of SVP depends on vascular compliance (distensibility).

• Increased intraocular pressure → decreased retinal venous volume → increased compliance → SVP more likely to appear.
• Decreased intraocular pressure → increased retinal venous volume → decreased compliance → SVP less likely to appear.

Venous Pulsation Pressure (VPP): defined as the minimum intraocular pressure at which the central retinal vein volume decreases sufficiently to pulsate in response to CSF pulsation. VPP may serve as a predictor of disease progression.

Q What is idiopathic retinal venous pulsation (SVP) an indicator of?

A

SVP is a candidate biomarker reflecting the relationship between intraocular pressure and intracranial pressure. In patients with glaucoma and idiopathic intracranial hypertension, the prevalence of SVP is reduced, and venous pulsation pressure (VPP) tends to be higher in glaucoma patients. Measuring SVP and VPP may allow indirect assessment of disease progression in idiopathic intracranial hypertension, glaucoma, and SANS, as well as the effects of pressure changes from goggles.

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7. Latest Research and Future Perspectives (Research-stage Reports)

For Patients: Please Read Carefully

The following content is currently at the research stage or under clinical trials and is not standard treatment available at general hospitals. It is reference information for professionals regarding future medical developments.

Equinox Multi-Pressure Dial (NPG)

The negative pressure goggles developed by Equinox have the following structure.

Device specifications: Lens with silicone seal, tube connecting goggles and pump, head strap for fixation, adjustable nose bridge. Available in three sizes (S, M, L), and a researcher-programmed pump generates negative pressure.

Three major clinical studies using this device are shown below.

Researcher	Subjects	Methods/Settings	Main results
Samuelson et al.	10 patients with open-angle glaucoma	-10 mmHg in one eye, atmospheric pressure in the control eye, applied for 8 hours	Tolerability score 1.8±0.4 (1=best), good safety confirmed
Ferguson et al.	—	Tono-Pen tip cover combined with NPG, 480 paired measurements at 4 pressure levels	Demonstrated accuracy and reproducibility of pneumatonometry under NPG
Swan et al.	65 patients	No negative pressure, 25%, 50%, and 75% of baseline IOP applied for 60 minutes	Clinically and statistically significant IOP reduction at all negative pressure settings

Samuelson et al. applied -10 mmHg negative pressure to one eye for 8 hours in 10 patients with open-angle glaucoma. The interest score was 1.8±0.5 (1=best, 10=worst), indicating high patient acceptability and favorable safety parameters.

Swan et al. applied negative pressure equivalent to 25%, 50%, and 75% of baseline IOP for 60 minutes in a randomized design involving 65 subjects. Clinically and statistically significant IOP reductions were confirmed at all negative pressure settings.

Positive Pressure Goggles and Spaceflight-Associated Neuro-ocular Syndrome (SANS)

• As a countermeasure for SANS, a method to correct abnormal pressure gradients caused by cephalad fluid shifts by increasing intraocular pressure is being studied.
• Previous studies (head-down tilt experiments) have confirmed that wearing swimming goggles increases the pressure gradient across the intraocular pressure and lamina cribrosa; positive pressure goggles intentionally and controllably achieve this.
• They may raise intraocular pressure more effectively than regular swimming goggles and help reduce SANS.
• However, the safety of long-term intraocular pressure elevation requires further research.

Q Are positive pressure goggles currently available for patients to obtain and use?

A

Currently not available for purchase or use. Pressurized goggles are investigational devices and have not been approved as standard clinical treatment. Safety and intraocular pressure-lowering effects were confirmed in both the Samuelson and Swan studies, but long-term efficacy and safety verification, as well as further clinical trials, are needed.

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8. References

1. Bonelli L, Menon V, Arnold AC, Mollan SP. Managing idiopathic intracranial hypertension in the eye clinic. Eye (London, England). 2024;38(12):2472-2481. doi:10.1038/s41433-024-03140-y. PMID:38789788; PMCID:PMC11306398.
2. Pereira S, Vieira B, Maio T, Moreira J, Sampaio F. Susac’s Syndrome: An Updated Review. Neuroophthalmology. 2020;44(6):355-360. PMID: 33408428.
3. Tan A, Fraser C, Khoo P, Watson S, Ooi K. Statins in Neuro-ophthalmology. Neuroophthalmology. 2021;45(4):219-237. PMID: 34366510.