Does Weed Help Glaucoma? Why Eye Doctors Say Not Really

Weed can lower eye pressure, but it isn't an effective glaucoma treatment. The drop only lasts three or four hours, so you'd have to get high around the clock to keep pressure under control, and cannabis may also reduce blood flow to the optic nerve. That's why the American Academy of Ophthalmology doesn't recommend it.

Glaucoma is an eye disease that damages the optic nerve, often because of increased intraocular pressure (IOP), the fluid pressure inside the eye. In the search for effective treatments, plenty of people have looked at cannabis because of its ability to lower IOP, and the idea has stirred up interest and controversy among doctors and patients alike.

So does treating glaucoma with weed actually work? Let's dig into it.

Glaucoma and weed: what is glaucoma?

Glaucoma is a group of eye conditions that damage the optic nerve, which carries visual information from the eye to the brain. This nerve is vital for good vision, and damage to it is often linked to high eye pressure, although glaucoma can also happen with normal eye pressure.

Glaucoma can show up at any age, but it's more common in older adults. It's one of the leading causes of blindness in people over 60. Many forms of glaucoma come with no warning signs, and the effect is so gradual that you may not notice any change in your vision until the condition is advanced.

Regular eye exams, including ones that measure eye pressure, are a big deal. If glaucoma is caught early, vision loss can be slowed or prevented. For people who already have glaucoma, treatment or monitoring will be needed for the rest of their lives.

Is weed good for glaucoma?

Glaucoma and other eye conditions can't be effectively treated with cannabis or cannabis-derived compounds like CBD. The main reason: eye pressure has to be controlled 24 hours a day to properly treat glaucoma, and that's just not practical with cannabis.

To lower eye pressure significantly and keep it down, you'd need to take 18 to 20 mg of THC six to eight times a day, every single day.

Consuming that much cannabis would seriously affect your mood, your mental clarity and, if you smoke it, your lungs. You also couldn't drive, operate machinery or handle a lot of everyday tasks. Not to mention the cost of using weed every three or four hours, which most patients simply couldn't afford.

Does weed affect your eyesight?

It isn't fully clear how cannabis affects eye pressure and glaucoma. It's possible that long-term cannabis use could damage the eyes or worsen vision in some patients.

What is clear is that high eye pressure isn't the only cause of optic nerve damage. The optic nerve can also be damaged by poor blood flow. That's a problem, because weed doesn't just lower eye pressure: it also lowers blood pressure throughout the body.

Cannabis may reduce blood flow to the optic nerve, effectively canceling out the benefit of lower eye pressure.

Until more research is done, the American Academy of Ophthalmology doesn't recommend marijuana or other cannabis products for treating glaucoma. The American Glaucoma Society agrees.

Weed and glaucoma: a story that goes way back

With the legalization of cannabis for medical and recreational use in a number of US states and in Canada, its possible usefulness for various health conditions has gotten a lot more attention.

Back in the 1970s and 1980s, research showed a measurable drop in intraocular pressure for three or four hours after smoking cannabis or taking THC as a pill or injection.

But keep this in mind: alcohol also lowers eye pressure for about an hour after a drink, and no doctor would ever recommend drinking every hour to treat glaucoma. There are plenty of other effective treatments that don't come with booze's side effects.

So what's the evidence that weed is good for glaucoma?

Several studies have tested THC in eye drops, pills and joints. The eye drops caused burning and irritation and didn't lower intraocular pressure. A sublingual THC compound (placed under the tongue) didn't lower intraocular pressure either.

In another study, glaucoma patients were given THC pills and joints. Within nine months, every single patient asked to stop the treatment because of the side effects.

Could CBD help with glaucoma?

CBD, a non-intoxicating cannabis compound, has gotten a ton of attention. But just like smoked or eaten cannabis, there's no conclusive research showing CBD is an effective treatment for glaucoma.

In fact, a recent study found that CBD may raise intraocular pressure, which could make glaucoma worse.

Scientists are looking into whether cannabis's active ingredients could someday lead to a glaucoma treatment. If the effects of cannabis compounds can be isolated, made longer-lasting and stripped of their side effects, they could lead to new treatments down the road.

That kind of breakthrough, though, needs a lot more research and is still years away.