Also referred to as intraocular pressure, or IOP, this is the result of the pressures exerted by the aqueous pressure and episcleral venous pressure. Aqueous humor is naturally produced by the eye’s ciliary body and relies on a complex outflow and drainage system through the canal of Schlemm. The industry gold standard for eye pressure measurement is the Goldman Tonometer. However, other methods, including the Non-Contact Tonometer (known as the air puff to most patients) have also been found credible. Normal eye pressure is considered to be 14-18 mmHg. However, pressure does increase slightly with age. Eye pressure of less than 9 mm Hg is considered hypotony and can lead to flattening of the globe. Meanwhile, eye pressure over 21 mm Hg is considered ocular hypertension. Very high pressures can be extremely painful for the patient and will cause blurry vision, halos, headache and nausea.
Elevated ocular pressure can irreversibly damage the retinal ganglion cells as well as the optic nerve. This phenomenon correlates to a group of ocular neuropathies that are known as glaucoma. A patient with IOP that is greater than 21 mmHg and significant visual field loss is considered a glaucoma patient. At this time, doctors treat glaucoma through various methods that are designed to lower intraocular pressure and stop visual field loss. However, while a normal IOP range is recognized, there is no such thing as a ‘safe’ pressure in glaucoma patients.
Cannabis has been shown to reduce eye pressure and help slow the progression of glaucoma.