Does cannabis help treat glaucoma or other eye conditions?
Glaucoma is one of the reasons given to justify the use of cannabis for medical purposes.
The results of research carried out the 1970 years show that THC can reduce intraocular pressure, a key factor in glaucoma. However, the use of eye drops containing THC or related compounds has been investigated, but it has not yet been possible to formulate an eye drop capable of introducing the drug into the eye in a sufficient concentration to be effective. . The first reports of this kind generated a lot of interest because at the time, conventional glaucoma medications caused a variety of unwanted side effects. But, as we'll see later, other treatments for this disorder have since overshadowed hemp-based medications. Conventional therapies for intraocular pressure outperform cannabinoids, and the next generation of glaucoma drugs are expected to treat the disease more directly or even reverse its course.
After cataracts, glaucoma is one of the leading causes of blindness worldwide, affecting more than 60 million people. Its most common form, the Primary open angle glaucoma (POAG), is a slowly growing disorder that destroys cells in the retina of the eye and degrades the optic nerve. These losses restrict the visual field, which eventually disappears, as well as the patient's sight.
3 risk factors
Researchers have yet to learn what triggers POAG, but they have identified three factors that put individuals at risk for developing the disease: age, race and high intraocular pressure. For example and according to the statistics: 1% of people aged 60 are suffering from POAG, while more than 9% of people over 80 are already infected.
The third risk factor, high intraocular pressure, results from the obstruction of the flow of fluid that helps the eye to maintain its rigid shape. Normally, this clear liquid, called aqueous humor, circulates between the front of the lens and the back of the cornea. In people with high intraocular pressure, the flow of fluid from the anterior chamber of the eye becomes restricted, causing pressure to build up like water behind a dam. Increased pressure in the eye contributes to glaucoma by decreasing the flow of nutrients to the optic nerve, scientists conclude. Since high pressure in the eye is the only significant risk of glaucoma that can be controlled, most treatments to date have been designed to reduce it. Unfortunately, reducing intraocular pressure does not always stop or even slow the progression of glaucoma to blindness.
Mixed opinion of experts
Cannabis and currently available derivative compounds like CBD are not necessarily an adequate treatment for glaucoma, nor for any eye condition. To treat glaucoma, eye pressure needs to be managed 24 hours a day. Cannabis is not a practical treatment for constant use. More research is still needed on the exact effects of cannabis and cannabis compounds on eye pressure and glaucoma.
Last month, study found that CBD appeared to increase pressure inside mouse eye, suggesting that the use of this substance in the treatment of glaucoma may in fact make the disease worse.
THEAmerican Academy of Ophthalmology does not recommend cannabis for the treatment of glaucoma. TheAmerican Glaucoma Society and Canadian Ophthalmological Society agree.
In detail
Medicines can change intraocular pressure by acting on different pathways of the aqueous humor. The trabecular meshwork, a mesh of connective tissue and cells, is an important flow pathway. Fluid flows through this tissue, into a small canal and outside the eye, where it joins the bloodstream. Drugs like epinephrine or dipevefrin work by changing the shape of certain cells, which improves circulation in the trabecular meshwork. Pilocarpine, another type of drug, contracts the muscle that controls the shape of the trabecular meshwork, making it easier for fluid to pass, while timolol, another type of drug, hinders fluid production by the ciliary epithelium. Other drugs, like apraclonidine and brimonidine, also reduce the amount of fluid produced. Finally, another type of drug simulates the production of agents that facilitate the passage of aqueous humor to the eye.
aqueous humor 
Trabecular mesh
There are also surgical options to control high intraocular pressure. The trabecular meshwork can be cut with a laser, which makes it easier for the fluid to come out. Alternatively, a surgeon can remove a piece of the wall of the eye and allow fluid to drain under the conjunctiva. Doctors may also insert tiny drainage tubes, similar to those used for middle ear problems, inside the eye to allow fluid drainage to the outer layers of the eye. Finally, laser, heat or cold can be used to destroy the ciliary epithelium, which secretes the aqueous humor.
TABLE Treatments for glaucoma
| Drug class | Examples | How does this reduce IOP |
|---|---|---|
| Beta-2 adrenergic agonists | epinephrine dipivine | Facilitates flow through the trabecular meshwork |
| Beta-2 Adrenergic Receptor Antagonists | timolol betaxolol | Removes the production of aqueous fluid |
| Cholinergic agonists | pilocarpine | Facilitates flow through the trabecular meshwork |
| Alpha-2 adrenergic receptor agonists | aproclonidine brimonidine | Reduces the production of aqueous fluid |
| Carbonic anhydrase inhibitors | acetazolamide dorzolamide | Reduces the production of aqueous fluid |
| Prostaglandin-F 2a similar | latanoprost unoprostone | Helps drain excess fluid |
| surgery | How does this reduce IOP | |
| Laser modification of the trabeculum | Improve the flow through the mesh | |
| Drain tube insertion | Helps drain excess fluid | |
| Destruction of the ciliary epithelium | Reduces fluid production |
Some cannabinoids reduce intraocular pressure
Several clinical studies have shown that some cannabinoids reduce intraocular pressure (IOP) as well as most conventional glaucoma medications. This is true that cannabinoids are administered orally, intravenously or by inhalation but not when applied directly to the eyes.
In most trials, a single dose of cannabis maintained this effect for three to four hours. In addition, reduced blood pressure may reduce blood flow to the optic nerve, negating the benefits of IOP reduction.
It is possible that future research will reveal a therapeutic effect for isolated cannabinoids other than THC or produce synthetic cannabinoid analogues that last longer and have fewer side effects. But the most promising line of research for the treatment of glaucoma lies in the development of therapies which can protect or save the optic nerve from damage or which can restore its blood supply. There is some evidence that a synthetic cannabinoid-like compound known as HU-211 has nerve-protecting properties, although it does not reduce IOP. HU-211 is chemically similar to THC, but it is not found in the marijuana plant and does not bind to the cellular receptor in brain cells that THC activates.
The takeaway from glaucoma is that:
The world's largest association of ophthalmologists and surgeons does not endorse cannabis or its derivatives as a treatment for glaucoma. Do not self-medicate to try to treat glaucoma. You can lose your sight if you do not have reliable and effective treatment for glaucoma. Several current and effective treatments for glaucoma are more reliable and safer than cannabis. If you have glaucoma, you should follow the advice of your eye doctor to get the treatment that's right for you.
SOURCE: NCBI et GLAUCOMATODAY
Read also : CANNABIS INFLUENCE ON VISION
