About three months ago I was diagnosed with glaucoma. I'm very nearsighted, which is a risk factor, along with age (I'm 73). The good news is that my eye pressure has dropped from 20-21 to 11-14 via prescription eye drops.
(Lowering eye pressure is the only way of preventing further optic nerve damage from glaucoma.)
Early on, though, I had a lot of anxious moments. After all, going blind from glaucoma or "just" experiencing functional loss of vision is scary.
My anxiety increased after my wife wondered if my use of CBD could have been a cause of the glaucoma. My first reaction was to tell her, of course not, because it's well-known that THC, another form of cannabis, lowers eye pressure.
But some Googling revealed numerous articles about how CBD raises eye pressure, so glaucoma patients should be wary of using it.
However, I've asked two optometrists and an ophthalmologist who specializes in glaucoma if I should stop using CBD. All three said "No."
Here's what one optometrist said in a reply to my question about whether I should be concerned. The small doses of CBD he refers to me using are 20 mg twice a day and 10 mg once a day, spread out during the day.
After his message I'll share additional reasons why I'm not worried about CBD raising my eye pressure.
Hello there ~ the article from the AAO [American Academy of Ophthalmology] you cited is likely referring to this study, which was performed at Indiana University in 2018:
In that study, the researchers found that dosing mice with THC (the active ingredient in marijuana) lowered eye pressure, while CBD transiently raised eye pressure. This information has been known for a while, but has perhaps become more relevant recently as CBD products have become more available.
While it is easy to draw conclusions from the study, I would caution you from throwing away all of your CBD product. Instead, I would draw your attention to this study, completed at the University of Aberdeen in 2006:
While the Indiana study was performed on mice, this study was performed with human subjects. Though the sample size was small (six individuals), it did provide some comforting information. The researchers found that while high doses of CBD (40 mg) did raise eye pressure, small doses (20 mg) had no effect. This suggests that small doses can likely be tolerated without producing eye pressure-raising effects.
Of course, much more research needs to be completed on human subjects for us to determine exactly what strength/dosage of these products is safe. But you can take heart that your small doses are unlikely to have a significant effect on your eye pressure.
My suggestion would be to continue your CBD use for now. If anything, prematurely stopping it would potentially color the results that your glaucoma medication provides. I would recommend continuing to keep your single doses at 20 mL/mg or below and spread them throughout the day.
We will be monitoring your eye pressure at each visit and should it start to creep up, we have other ways to bring it down than for you to cease your CBD treatment. At this point, I wouldn’t stress about it too much.
Good advice. I've stopped stressing about using CBD entirely, for these reasons.
First, the December 2018 IOVS Journal article described how eye pressure in mice responded to doses of THC and CBD. Mice aren't people, obviously. The article says:
Three of four studies that have tested CBD for effects on IOP [intraocular pressure] have reported no effect, but the fourth has reported an increase in IOP.
Somewhat strangely, the article doesn't give references to the three studies that showed CBD having no effect on eye pressure, just the single study that reported an increase.
But that study was the 2006 University of Aberdeen research which my optometrist referred to as showing that only a CBD dose of 40 mg raised eye pressure, while 20 mg of CBD had no effect. Since I assume the other three no-effect studies mentioned in the IOVS Journal article also were on humans, seemingly the only evidence that CBD raises eye pressure in people is the 2006 study.
Then there's the issue of CBDA, a precursor of CBD that an Oregon State University lab study found prevented cells from being infected by the coronavirus. I've been using CBDA rather than CBD for about a week, as described in my blog post, "I got some CBDA. Covid can't touch me now!"
I'm no expert on the pharmacology of CBD and CBDA. However, it seems to me that CBDA is even less likely than CBD to raise eye pressure, since CBD and CBDA work in considerably different ways. Meaning, the mechanisms by which they have effects on the human body are different.
The IOVS article says "there is no effect on IOP by CBD if GPR18 and CB1 are both blocked/deleted." In other words, eye pressure in the mice didn't increase if the receptors GPR18 and CB1 weren't functional.
I found a lengthy study that looked at how various forms of cannabis operate. In the CBDA section, it says:
Bolognini et al. (2013) also found that, in contrast to CBD (section 7.3.1), CBDA did not display significant activity as either an agonist or an inverse agonist at cannabinoid CB1 receptors in mouse whole brain membranes, even at a concentration 100,000-fold higher than a concentration (0.1 nM) at which it potentiated 8-OH-DPAT in rat brainstem membranes.
I don't understand much of that language, but it seems clear that CBDA didn't have any significant activity at the CB1 receptor that could cause CBD to raise eye pressure at high doses.
So I'm comfortable with using CBD even though I have glaucoma, and I'm considerably more comfortable with using CBDA.