What Are the Causes of Glaucoma Other Than High Eye Pressure

It is commonly believed that high eye pressure causes glaucoma. This article highlights the role of ocular perfusion pressure in the causation of glaucoma. Dr. Weinreb and his colleagues have suggested how low ocular perfusion pressure (OPP) is responsible for the development and progression of glaucoma.

What Is Ocular Perfusion Pressure?

Ocular perfusion pressure is the difference between intraocular pressure (eye pressure) and blood pressure. If the eye pressure is high and blood pressure is normal, or the eye pressure is normal and blood pressure is low, both conditions will lead to low ocular perfusion (poor blood supply especially to the optic nerve). This leads to gradual death of nerve fibers of optic nerve which is the cornerstone of glaucoma.

It is important to note that not all patients who have high intraocular pressure (eye pressure), have glaucoma. Also, even patients with normal intraocular pressure may have glaucoma. This suggests that apart from intraocular pressure, there are other factors also responsible for glaucoma.

Statistical evidence confirms that low ocular perfusion pressure causes ischemia (inadequate blood supply) to the optic nerve where it is attached to the eyeball. This results into damage to the nerve fibers in the optic nerve and visual field defects.

The ocular perfusion pressure depends on multiple factors such as the position of body – whether erect or recumbent, the blood pressure and its variation over 24 hours and the medications used for high blood pressure.

Low diastolic blood pressure and reduced nocturnal blood pressure have been found to be associated with glaucoma. Migraine and Raynaud phenomenon are also associated with glaucoma.

The clinicians should always keep in mind the role of ocular perfusion pressure and blood pressure in the pathogenesis of glaucoma. This understanding will not only help them manage the related factors but also make them convey realistic expectations to the patients about their condition.

Patients generally know that glaucoma is caused by high intraocular pressure (IOP) and if IOP is controlled well, glaucoma will be controlled completely. They need to understand that glaucoma may progress in spite of excellent IOP control with medication or surgery because of factors such as low ocular perfusion pressure.

Reference: The Role of Perfusion Pressure

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