Glaucoma is a condition that causes damage to your eye’s optic nerve and gets worse over time. It’s often linked to a buildup of pressure inside your eye. Glaucoma tends to be inherited and may not show up until later in life. Most people with glaucoma have no early symptoms or pain. Without treatment, glaucoma can cause total permanent blindness within a few years. It’s the result of high fluid pressure inside your eye. This happens when the liquid in the front part of the eye doesn’t circulate the way it should.
There are two main kinds:
- Open-angle glaucoma. It’s the most common type. Your doctor may also call it wide-angle glaucoma. The drain structure in your eye — it’s called the trabecular meshwork — looks normal, but fluid doesn’t flow out like it should.
- Angle-closure glaucoma. It’s less common in the West than in Asia. You may also hear it called acute or chronic angle-closure or narrow-angle glaucoma. Your eye doesn’t drain right because the angle between your iris and cornea is too narrow. Your iris is in the way. This can cause a sudden buildup of pressure in your eye. It’s also linked to farsightedness and cataracts, a clouding of the lens inside your eye.
Detecting glaucoma early is one reason you should have a complete exam with an eye specialist every 1 to 2 years. Occasionally, pressure inside the eye can rise to severe levels. In these cases, you may have sudden eye pain, headache, blurred vision, or the appearance of halos around lights.
If you have any of the following symptoms, seek immediate medical care:
- Seeing halos around lights
- Vision loss
- Redness in the eye
- Eye that looks hazy (particularly in infants)
- Nausea or vomiting
- Eye pain
- Narrowed vision (tunnel vision)
How Can Cannabis Help Treat Glaucoma?
The ability of cannabis to improve the symptoms of glaucoma has been demonstrated in various studies, but doubts still remain over its efficacy and consistency within patient populations. Despite this, many medical cannabis patients utilize cannabis for glaucoma, and report subjective improvements in various symptoms.
Reduces intraocular pressure
Increased intraocular pressure (ocular hypertension) is the risk factor in the majority of glaucoma cases, although it is absent in certain populations in almost 50% of individuals suffering from open-angle glaucoma (OAG)—the most common type, comprising around 90% of all cases. Intraocular pressure is determined by the production of aqueous humour in the eye coupled with the rate of drainage of the aqueous humour via the trabecular meshwork, a spongy tissue located at the base of the cornea. Consistently high intraocular pressure can cause progressive damage to the optic nerve and the retinal ganglion cells that contain light-sensitive photoreceptors. If damage is severe enough, total blindness can result. Canasol has been demonstrated to be effective in lowering intraocular pressure, and has also been shown to potentiate the effectiveness of other widely-used glaucoma drugs such as Timolol. Recently, a new and improved drug was developed by the same research team; this drug is known as Cantimol, and contains Canasol and Timolol, but has not yet been approval for market. Canasol contains no psychoactive cannabinoids and has also been widely prescribed by physicians in the USA and Canada—and has apparently been used by patients in the UK and Australia too, despite not having market approval or a legal precedent for use.
A common phenomenon found in glaucoma patients is mydriasis, in which the pupil becomes dilated. In fact, it is thought that extreme mydriasis may actually cause the characteristic bulging-out of the iris in attacks of closed-angle glaucoma—in order for the pupil to dilate, muscle tissue in the iris (known as the dilator pupillae) must contract. When muscle tissue contracts, it bulges, and in extreme cases this bulging tissue can expand into the anterior chamber (the fluid-filled space between the iris and cornea) and press up against the cornea, totally preventing escape of aqueous humour via the anterior chamber and into the trabecular meshwork.
The opposite of mydriasis is miosis (not to be confused with the form of cell division known as meiosis). Miotic drugs are highly useful in glaucoma treatment, not only CAG, as constriction of the pupil allows increased drainage of aqueous humour into the trabecular meshwork. Cannabis has been shown to possess miotic properties on various occasions, including one notable case of apparent acute cannabis poisoning in a 20-month-old infant.
Acute glaucoma can cause rapid loss of vision due to total blockage of the fluid drainage channels (© Community Eye Health)Acute glaucoma can cause rapid loss of vision due to total blockage of the fluid drainage channels (© Community Eye Health)
While the majority of glaucoma cases are painless, the rarer form of the disease (known as closed-angle glaucoma or CAG) is characterized by sharp, stabbing pains in the eyeball and rapid loss of vision, which may be permanent if not given medical attention. Closed angle glaucoma differs from the more common form in that it produces acute symptoms instead of chronic (and generally painless) symptoms. An attack of CAG is considered a medical emergency, and occurs due to a total blockage of the trabecular network (rather than a progressively reduced ability to drain aqueous humour, as with OAG) caused by a sudden bulging forward of the iris.
Cannabis has been proven time and time again to be a useful and effective anti-inflammatory for a range of different conditions, although no formal studies have been conducted on the potential of cannabis to reduced glaucoma-related inflammation. As understanding of the role inflammation has to play in the progression of the disease increases, it may well prove to be the case that cannabis also provides relief to glaucoma patients due to its anti-inflammatory properties.
Attacks of closed-angle glaucoma are often accompanied by secondary symptoms of nausea and vomiting, which is believed to arise as a result of a phenomenon known as the oculoemetic reflex. Various past studies have shown an association with ophthalmic surgery and post-operative vomiting (particularly squint surgery, which causes vomiting in 41% of patients), which gave rise to the possibility of the oculoemetic reflex existing.
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