Glaucoma is a group of eye conditions whose hallmark is high pressure in the eye, known as intraocular pressure or IOP, which can damage the optic nerve. Although people of any age can get glaucoma, it is more common in older adults. It is one of the principal causes of blindness for those over the age of 60. Studies have shown that marijuana can effectively reduce intraocular pressure in the eyes.
Types of glaucoma
There are many forms of glaucoma, but the main two are open-angle and angle-closure. Open-angle glaucoma is by far the most common, with at least 90 percent of glaucoma cases of this type.
In open-angle glaucoma – so-called due to a wide, open angle between the cornea and iris – the eye’s drainage canals slowly clog over time, which causes increased eye pressure. Because the disease develops so gradually, many symptoms and resulting damage may not be noticed until significant damage is done. This has also proven to be the case for many other types of glaucoma. Once symptoms are noticed, they tend to be patches of blind spots either in the central or peripheral vision. This could be in one eye but often occurs in both. The patient in advanced stages can have tunnel vision.
Although not as common as open-angle glaucoma, angle-closure glaucoma is nevertheless more common than the other types. Working the opposite of open-angle, in the patient with angle-closure, the eye’s drainage canals are blocked quickly, which causes a sudden rise in IOP. The area between the cornea and the iris has a narrow angle or is even closed. Due to angle-closure glaucoma developing so quickly, the symptoms as well as the damage are quite noticeable, and the patient needs immediate medical intervention. Symptoms may include the following:
- Eye pain
- Blurred vision
- Red eyes
- Halos around lights
- Nausea and vomiting
- Severe headache
There are at least nine other forms of glaucoma that are somewhat rare, but the most common of these are normal-tension glaucoma and congenital glaucoma³. Normal-tension glaucoma is just about what it sounds like – the tension, or pressure in the eye, is normal or may be slightly elevated, yet the optic nerve is still damaged. Congenital glaucoma may be inherited and happens when the drainage canals in an unborn baby’s eyes do not develop correctly or they develop incompletely. Surgery can often correct this.
Marijuana and glaucoma
Some studies done on marijuana and glaucoma have shown that IOP can be lowered as much as 65 percent, while the mean reduction in another study was around 25 percent. This effect occurred whether cannabis was smoked, ingested, administered intravenously or sublingually (under the tongue). Unfortunately, the effect lasted only about 3 to 4 hours. The degree of IOP reduction also depended on the dose, although higher doses did not make the pressure-lowering effects last longer.
A glaucoma and marijuana study using mice, which was performed by the University of Indiana, yielded surprising results – cannabidiol, or CBD, made the eye pressure worse. After four hours, eye pressure was raised 18 percent. On the other hand, when researchers administered THC alone, the IOC in male mice was reduced 30 percent. The reduction for female mice wasn’t as substantial at only 17 percent, prompting researchers to question whether females are less sensitive to THC than males. Additional information gleaned from this study was that of the neuroreceptors affected; CB1 and GPR18. Researchers say this may have important implications for future research in this area.
Another study of glaucoma and cannabis, done at the University of Aberdeen, UK, showed good results using synthesized THC. The study was done on human patients using sublingual THC and CBD. In this study, CBD increased the eye pressure short-term, while THC reduced it. 5 mg sublingual doses of Delta-9-THC were given which caused a reduction in IOP; plus it was well tolerated by most. 20 mg of CBD did not reduce IOP, and 40 mg caused IOP to rise.
What does this mean for you?
Unfortunately, not enough studies have been done to definitively say whether patients should use cannabis to treat their glaucoma, and the research points to CBD as possibly doing more harm than good. And CBD curtails the effect of THC as well, so a product with large amounts of CBD would probably not be ideal.
Which of course doesn’t mean that THC would not help. Everyone is different, and each case of glaucoma is different. Many glaucoma patients insist that marijuana helps with their condition and refuse to be without it.
If you have glaucoma and wish to try marijuana to help relieve your eye pressure, you should check with your doctor, or find a doctor who is educated in glaucoma and marijuana and can guide you.
Please check the medical marijuana laws of your state and find out if glaucoma is considered a qualifying medical condition for marijuana use. You can use this map to get started.
3. Glaucoma Research Foundation
4. Marijuana and Glaucoma, Glaucoma Today
5. CBD in marijuana may worsen glaucoma, raise eye pressure, Indiana University
6. Effect of sublingual application of cannabinoids on intraocular pressure: a pilot study, Institute of Medical Sciences, University of Aberdeen