Marijuana’s role in optometry and beyond

Seattle-Bob Prouty, OD, FAAO, educated a packed house at the American Optometirc Association’s Optometry’s Meeting on marijuana’s use in and outside of eye care.

Because his father was a police officer, Dr. Prouty has never used marijuana, medically or otherwise. But that doesn’t mean he doesn’t see the potential benefits-or harms-of medical marijuana.

His eyes were opened to the drug’s potential medical benefits after seeing Sanjay Gupta’s report on CNN about Charlotte Figi, a small child from Colorado who was suffering from Dravet Syndrome, a rare, severe form of intractable epilepsy. As a toddler, Figi suffered from 300 grand mal seizures a week. Her parents were able to find a type of marijuana that was high in cannabidiol (CBD) but low in tetrahydrocannabinol (THC), the intoxicant. They were able to use the oil from this strain of marijuana to greatly reduce Figi’s seizures. You can read Charlotte Figi’s story here.

Related: Marijuana and optometry: Practicing post-legalization

At a federal level, marijuana remains a Schedule I drug. While the attitudes about marijuana seem to be shifting across the country, to date only four states have completely legalized marijuana-Colorado, Washington, Oregeon, and Alaska-which has made studying the drug and its effect on various diseases and conditions rather difficult.

In 1997, the Institute of Medicine released a report on medical marijuana.

“While there was a remarkable conscientious about the potential of cannabinoid drugs for medical use, there was far less convincing data about the proven medical benefits about whether this should be utilized at all,” he says. “A review of the science behind marijuana and cannabinoids suggests that the debate so far has been very much misunderstood. Medical use of potent, controlled psychoactive drugs has not led to abuse, based on that report. Rather than focusing on the drug control policy, the medical marijuana debate should really be more about future drug development.”

Under the guidance of a well-educated and involved doctor, there are certain cases in which medical marijuana can be used proactively and appropriately, says Dr. Prouty.

But does that extend to eye care?

Next: Marijuana as a glaucoma treatment

Marijuana as a glaucoma treatment

Glaucoma is currently listed as a condition that can be treated with medical marijuana, but Dr. Prouty asserts that there is no evidence that it is a better treatment than the traditional medicines currently available.

When medical marijuana advocates discuss the drug’s use as a glaucoma treatment to lower intraocular pressure (IOP), they refer to a study from the 1970s when glaucoma treatment was nothing compared to what is available today.  

“The first such reports generated considerable interest at the time because the conventional medications just had such an adverse side-effect profile,” says Dr. Prouty. “Currently, other treaments of the disorder have massively eclipsed what marijuana-based medicines can do.”

Related: AAOphth says marijuana is not proven treatment for glaucoma

While we know that marijuana does lower IOP, researchers are not yet sure how or why it does so. And in most trials, marijuana maintains IOP reduction for only three to four hours.

“How many times is that smoking in a day? Eight times a day. So, you’ve got to be dosed out of your gourd for this to have any effect,” says Dr. Prouty.

Marijuana lowers blood pressure, and reduced blood pressure could decrease the blood flow to the optic nerve, thereby contracting from the benefits of lowering IOP. Without further researcher, Dr. Prouty says the benefits of lowering IOP are outweighed by the potential harm.

“So, they’re having a good time going blind,” he says.

Next: Is it helping or hurting?

Is it helping or hurting?

Marijuana is often written off as a gateway drug, leading its users down a dangerous path toward much more addictive and dangerous drugs.

“Because it’s the most widely-used illegal drug, marijuana is predictably the first one that most people are going to encounter, including people who are going to experiment with other substances. The vast majority of them, however, are first acquainted with alcohol and nicotine, usually when they were too young to participate with that legally,” he says. “It is a gateway drug in that in generally precedes other forms of illicit drugs. On the other hand, marijuana does not appear to be a gateway to the extent that itcauses or even is a significant predictor of hard drug abuse.”

Instead, the better predictor that someone will move onto hard drugs is his intensity of use of marijuana and other predispositions for addiction.

“There are many reasons to worry that for people who choose to use marijuana as medicine-especially those who smoke it-the drug could actually add to their health problems-not be helping but hurting,” says Dr. Prouty.

Whether or not marijuana is addictive is a hot topic, says Dr. Prouty.

“Yet, when you have candid discussion with most marijuana users, they’ll tell you they quickly develop a tolerance to its effects and tend to want to use it more,” he says. “That’s akin to addiction.”

Related: Cannabinoids-medical perils and benefits

Active marijuana users experience some degree of withdrawal symptoms, including restlessness, irritability, agitation, insomnia, sleep disturbances, nausea, and cramping-uncomfortable, but far milder than those withdrawal symptoms of alcohol or hard drugs, says Dr. Prouty.

“For certain patients-particularly adolescents, people with psychological problems, those with inherent disposition toward substance abuse-marijuana-based medications may not be worth the work,” he says.