The entire retina is part of the CNS, aka “the brain”. The optic nerve is therefore part of the brain.

There are dopaminergic amacrine cells within the retina and dopamine receptor much more widely.

Here is a reference with some of original citations:

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2865197/#R36

This is cool, thanks for sharing!

A cursory googling led here:

> Dopamine is a key neurotransmitter in the signaling cascade controlling ocular refractive development, but the exact role and site of action of dopamine D1 receptors (D1Rs) involved in myopia remains unclear.

[.. snip ..]

> Therefore, activation of D1Rs, specifically retinal D1Rs, inhibits myopia development in mice. These results also suggest that multiple dopamine D1R mechanisms play roles in emmetropization and myopia development.

https://www.jneurosci.org/content/43/48/8231