Low Intracranial Pressure Could Trigger Glaucoma Risk

Additional proof that intracranial pressure contributes significantly to normal-tension glaucoma, which causes up to 50% of all instances of glaucoma, is offered by an international team of researchers led by Lithuanian researchers. Low intracranial pressure is associated with decreased patient visibility, particularly in the nasal zone, according to a new clinical investigation.

Optic nerve degeneration is the primary cause of glaucoma, one of the main causes of blindness in persons over 60. Patients with glaucoma frequently have elevated intraocular pressure (IOP), also known as eye pressure. However, glaucoma may not always develop in those with ocular hypertension. Additionally, individuals with normal IOP may nevertheless acquire glaucoma. The prevalence of so-called normal tension glaucoma (NTG) in the world’s population is between 30 and 90 percent.

“Contemporary medicine has methods to treat elevated eye pressure and to slow or even stop the damage to the optic nerve. However, these methods do not work in the case of normal tension glaucoma. There is a growing awareness among the scientific community, that glaucoma is a condition caused by two pressures—inside the eye and the skull,” says professor Arminas Ragauskas from Kaunas University of Technology (KTU), Lithuania.

The non-invasive intracranial pressure measurement method utilized in the study detailed below was developed by Ragauskas, Head of the Health Telematics Science Institute at KTU.

He continues by describing how the optic nerve is anatomically encased in cerebrospinal fluid and connected to the brain. The health of the optic nerve can be impacted by both intracranial pressure (ICT), or the pressure inside our skull as measured in the cerebrospinal fluid, and intraocular pressure (IOP). Translaminar pressure differential (TPD), or the balance between the two pressures, and its relationship to the onset of glaucoma have recently attracted the attention of researchers.

Possible Link Between Brain Pressure & Glaucoma Identified

Researchers from Lithuanian, Israeli, and American universities have enrolled 80 early-stage normal tension glaucoma (NTG) patients. The 300 NTG patients who were referred to the Eye Clinic at the Lithuanian University of Health Sciences between January and October 2018 were the subjects.

Throughout the trial, a number of measurements were taken, including intraocular (IOP), intracranial (ICP), and visual field perimetry. TPD = IOP—ICP was the formula used to compute the translaminar pressure difference (TPD). Five zones—nasal, temporal, peripheral, central, and paracentral—were identified in the visual field.

The research found multiple statistically significant associations between changes in the visual field, intracranial pressure, and TPD. The patient’s visual field suffered more substantial damage the higher the TPD. The nasal zone saw the greatest decrease in the visual field.

“Visual field loss means only one thing—a person is becoming blind. That’s why it is so important to understand the causes of this condition and to reverse it. We are all aware of the dire outcome,” says Prof Ragauskas.

Researchers conclude that higher TPD could be estimated as a risk factor for the negative development of normal tension glaucoma. As translaminar pressure difference is calculated by subtracting ICP from IOP, the lower the intracranial pressure measure, the higher the TPD. Thus, in normal-tension glaucoma, lowered intracranial pressure is a possible risk factor.

Technology Invention by Lithuania Used in Study

“The idea that brain pressure is related to the visual field is not new. Several years ago, we conducted a series of experiments studying the links between visual field and intracranial pressure, using the non-invasive technology developed here, at KTU. In the conferences that followed, I saw how our new idea was met with excitement by the international community of ophthalmologists,” says Prof Ragauskas.

The relationship between intracranial pressure and glaucoma provides new opportunities for medical researchers to examine the cause and potential therapies for this condition. Science organizations working globally have been producing evidence in favor of this concept. According to Prof. Ragauskas, his research has both directly and indirectly added to the body of knowledge on the subject.

The two-depth Transcranial Doppler (Vittamed UAB, Lithuania) used for the intracranial pressure measurement was created by Prof. Ragauskas’ team in the labs at Kaunas University of Technology. Prof. Ragauskas’ invention enables non-invasive ultrasound measurement of intracranial pressure through the eye, as opposed to the conventional method, which requires drilling a small hole into the patient’s skull. The invention has received several industrial patents in the US and Europe.

“We are not competing with invasive methods, but heading towards an entirely new direction. At the moment, I see that ophthalmology is the field where our technology is needed most, and we are using it for research purposes. However, we are constantly developing our invention and have recently patented a couple of new applications, which might be used in other contexts where measuring intracranial pressure is crucial. For example, in long-term space missions,” says KTU professor Ragauskas.

The findings are published in the journal Diagnostics.

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