Many of the patients who use cannabis for glaucoma therapeutic purposes describe subjective improvements in different symptoms. Glaucoma is a common eye disease, the frequency of which increases with age. Acute glaucoma can cause rapid loss of vision due to complete obstruction of the fluid drainage channels.
Reduces intraocular pressure
Increased intraocular pressure (ocular hypertension) is the risk factor in most cases of glaucoma. Constant high intraocular pressure can cause progressive damage to the optic nerve and the ganglion cells of the retina, which contain the light sensitive photoreceptors. If the damage is severe enough, it can cause total blindness. Pharmacologist and professor Manley West conducted landmark research on cannabis as a potential glaucoma treatment, alongside leading ophthalmologist Dr. Albert Lockhart. As a result of their work, which began in 1964 and investigated the traditional use of cannabis in the communities of Jamaica, they developed a cannabis-based eye drop, and obtained approval to market their product in Jamaica under the name “Canasol”, in 1987.
A common phenomenon found in glaucoma patients is mydriasis, which causes the pupil to dilate. In fact, it is believed that acute mydriasis can cause the characteristic swelling or edema of the iris in cases of angle-closure glaucoma, also called acute glaucoma.
The opposite of mydriasis is miosis (not to be confused with the form of cell division known as meiosis). Miotic medications are very useful in the treatment of glaucoma, not only of GAC, since the contraction of the pupil allows to increase the drainage of the aqueous humor towards the trabecular meshwork. Cannabis has been shown to possess miotic properties on several occasions.
The broad-spectrum efficacy of cannabis, as a pain reliever, mood enhancer, and muscle relaxant, can provide subjective relief to people suffering from acute attacks of angle-closure glaucoma.
Cannabis has been shown to be a useful, and effective, anti-inflammatory agent for a number of different diseases, although no formal studies have been conducted on the potential of cannabis to reduce glaucoma-related inflammation. As the role that inflammation plays in disease progression is better understood, it could be shown that cannabis also provides relief to glaucoma patients due to its anti-inflammatory properties.
Anti-nausea / antiemetic
Angle-closure glaucoma attacks are often accompanied by secondary symptoms of nausea and vomiting. These secondary symptoms are believed to appear as a result of a phenomenon known as the eye-emetic reflex.
It is not known exactly what role the endocannabinoid system plays in regulating vomiting, but it has been shown that cannabinoid receptor agonists, such as THC, appear to directly suppress vomiting and nausea by agonizing the CB1 receptor, while antagonist receptors CB, like CBD, are neutral, and inverse agonists actually cause nausea.