Elevated IOP is considered the main risk factor for glaucoma progression, but some forms of the disease may present without this finding. A new study suggests that intracranial pressure may also play an important role in glaucoma, since the optic nerve is surrounded by cerebrospinal fluid in the suprachoroidal space.

The team evaluated 95 patients with normal-tension glaucoma, 60 patients with high-tension glaucoma and 62 healthy subjects. They found that the mean intracranial pressure of normal-tension glaucoma patients was significantly lower than that of healthy subjects (9.42mm Hg vs. 10.73mm Hg). This value decreased even more in those with high-tension glaucoma (8.11mm Hg).

The researchers noted that their study results contradict those found in Asian and American populations. They added that differences may have resulted from body position (lateral decubitus vs. supine position), as this influences intracranial pressure; cerebrospinal fluid location (lumbar vertebrae vs. optic nerve); or intracranial pressure and IOP fluctuation over time, which makes measuring elevated pressures at certain times difficult.

The researchers concluded that in normal-tension glaucoma, “the abnormal intracranial pressure value on lamina cribrosa could be one of the many factors influencing optic nerve degeneration of normal-tension glaucoma patients and should be considered as such instead of being regarded separately as just a ‘low intracranial pressure.’”