Kia Ora,

We made it... kind of. I've split this final article into two since it became really long! Thank you for reading so far. Being able to write these newsletters has kept me accountable for learning this interesting topic. I've appreciated all the feedback so far. If you have any more, please hit reply.

If you missed any of this, we are exploring Cannabis (in Te Reo Māori, Taru rauhae) and its possible use to treat Glaucoma (Papahewa).

So far, we learned about:

• how the eyes works,

• what glaucoma is, and

• current ways to treat glaucoma.

Now, we will look into: what is Cannabis and the Endocannabinoid system. The legal implications of Cannabis in Aotearoa New Zealand (NZ) as well as Australia, the United Kingdom (US) and the United States of America (US).

Cannabis and it's controversial history

The 2020 Cannabis referendum saw Aotearoa divided. Unlike the End of Life Choice referendum, where almost two-thirds of Kiwis voted in support of the bill, the proposed Cannabis legalisation bill lost only by a slim margin. 48.4% voting supporting legalisation and 50.7% voting against (New Zealand Gazette Te Kāhiti o Aotearoa, 2020). Already, we can see Cannabis grabs the spotlight, splitting the nation.

Described as a group of plants (such as Cannabis sativa and Cannabis indica), the Cannabis extracts have been used for thousands of years. In ancient China, India and Egypt, they have been used in various treatments, including pain during childbirth, malaria, and constipation. Fast-forwarding to the 1970s, the United Kingdom, the United States and Canada banished Cannabis to the realm of crime and illicit substance use due to its psychotropic nature (Amin & Ali, 2019).

Recently, there is a resurgence in Cannabis's therapeutic benefits. Cannabis is proven effective in treating chronic pain, and reducing nausea and vomiting caused by chemotherapy (The Health Effects of Cannabis and Cannabinoids, 2017). And, what will be relevant to us is its ability to possibly treat glaucoma by lowering eye pressure (Hepler & Frank, 1971).

Despite losing on the referendum, recent amendments to New Zealand legislation have lead to better access and production of Cannabis for medicinal purposes (NZ Drug Foundation Te Tūāpapa Tarukino o Aotearoa, n.d.). With this increased attention, let's look deeper into Cannabis.

What is Cannabis?

The Cannabis plants contain over 400 different compounds. 60 of these compounds have a psychoactive effect and are called cannabinoids (or more specifically phytocannabinoids, phyto- being associated with plant). There are two cannabinoids, which are particularly interest. These naturally occurring cannabinoids provide the strongest effects on the human body, and they are:

1. Δ⁹-Tetrahydrocannabinol (Δ⁹-THC)

2. Cannabidiol (CBD)

Δ⁹-THC is the main psychoactive component of Cannabis. It's what provides the 'high' in recreational use (Ashton, 2001). CBD is thought to provide the medical component of Cannabis (Black et al., 2019), even dampening the unwanted effects of THC.

Consumed in various ways, Cannabis can be inhaled by burning plant matter in 'joints' or 'pipes'. It can also be eaten by baking into cakes and cookies (Ashton, 2001).

Cannabinoids interact with the body's own Endocannabinoid system which is what we will explore next.

The Endocannabinoid system

The Endocannabinoid system (ECS), present in the vertebrates (living beings with a spine), mammals and humans, is responsible for many functions. These range from appetite to the heart, fertility to immune functions, and memory to pain. Loss of normal functioning precipitates into disease (Battista et al., 2012).

The ECS comprises endocannabinoids, which are neurotransmitters (chemical signals between nerve cells) and receptors (special proteins that receive signals).

They main two endocannabinoids are:

• N-arachidonoyl-ethanolamine (anandamide or AEA), and

• 2-arachidonoylglycerol (2-AG).

The two main receptors for endocannabinoids are found in the nervous system cells (such as the brain and even the eye). They are:

• Cannabinoid Receptor 1 (CB1), and

• Cannabinoid Receptor 2 (CB2).

Other receptors are also: GPR18 and GPR119 (Straiker, 2019).

Endocannabinoids acts on these receptors to produce these intended human functions. Phytocannabinoids and synthetics cannabinoids can also activate these receptors.

The legal status of prescribing in Aotearoa (and Australia, United States and the United Kingdom)

Now we know what Cannabis is, let's take a step back and look at the legality of Cannabis use.

In Aotearoa, despite still being illegal to possess for recreational use, Cannabis is allowed for medical purposes. This requires a prescription from a doctor (Ministry of Health Mānatu Hauora, 2021). In Australia, this is similar, although there might be some variation at the state level (Therapeutic Goods Administration, 2017). The UK marches to the same rhythm, acceptable for medical use only, granted with doctor's prescription (UK Legislation, 2018).

In the US, Cannabis is treated differently for both recreational and medicinal use. Cannabis is illegal for all uses at the federal level. On the other hand, state-level laws supersede this blanket ban. States like California allow controlled recreational and medical use (National Conference of State Legislatures, 2019).

But, what about the role of optometrists as medicine prescribers?

First we need to look at:

• prescribing, and

• optometrists and required additional training.

In Aotearoa, authorised prescribers are described as the only individuals who can prescribe medicines. Authorised prescribers include medical practitioners (i.e. doctors), nurse practitioners (nurses with additional, high-skill training) **and also optometrist (New Zealand Parliamentary Counsel Office Te Tari Tohutohu Pāremata, 2017).

Because optometrists are considered authorised prescribers, they can prescribe medicine within their scope (i.e. treating eye problems). However, there is a condition to this.

Optometrists, in Aotearoa, are governed by the Optometrists and Dispensing Optician Board Te Poari o ngā Kaimātai Whatu me ngā Kaiwahakarato Mōhiti (ODOB). According to the ODOB, optometrists are required to have an authorised scope to prescribe medicine. Furthermore, an optometrist must fulfil additional prerequisites to prescribe glaucoma medication. This additional glaucoma endorsement involves additional training, such as completing extra certification or performing twenty hours of observation under a glaucoma-specialised practitioner (Optometrists and Dispensing Opticians Board Te Poari o ngā Kaimātai Whatu me ngā Kaiwahakarato Mōhiti, n.d.).

This means an optometrist without an endorsement can not prescribe medicine, or an optometrist with an endorsement can prescribe medicine but not medicine related to treating glaucoma without extra glaucoma credentialing.

This is similar for optometrists in Australia. The Optometry Board of Australia conducts affairs for Australian optometrists. Board-approved optometrist must have a medicines endorsement to prescribe medication. This includes glaucoma. What is prescribed is limited to a list of medications (Optometry Board of Australia AHPRA, 2019). What differs is NZ optometrists have more flexibility in what can be prescribed, so as long as it is to treat the eye. This works well if drugs change or need to be substituted.

In the UK, the General Optical Council acts as the legal representation of opticians and optometrists. To prescribe medical drops in the UK, an optometrist will need to become an independent prescriber. This often involves extra training. A particular prescribing field is chosen within this training — such as glaucoma (General Optical Council, 2015).

Finally, the United States is slightly different. Optometrists are state-certified. Extra authorisation is required to prescribe medicine. This is known prescriptive authority (National Conference of State Legislatures, 2018).

With the right credentialing, optometrists in these countries can treat glaucoma. And with glaucoma treatment, the question arises: can medicinal cannabis be used to treat glaucoma?

Conclusion

Cannabis's controversy is enough to split Aotearoa in two. That's what we saw with the 2020 Cannabis referendum. A long history of therapeutic use has seen the plant make a comeback despite its recreational restrictions.

Cannabis is a plant containing many chemicals. Δ⁹-Tetrahydrocannabinol and Cannabidiol are of particular intrigue due to their psychoactive but also medicinal attributes.

With recent legislative changes, Cannabis is legal for use medically in Aotearoa, Australia, the United States, and the United Kingdom.

Optometrists who have the correct credentialing can prescribe medicines to treat certain eye conditions, including glaucoma.

Then, the question asked: what about using medicinal cannabis to treat glaucoma? This is what we will explore in the next newsletter.

Thanks for reading please forward this on to family and friends if you thought this was interesting.

All the best for the week ahead.

Ngā mihi,

Shivan :)

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