Very possibly because the olfactory bulb is basically a bit of the brain exposed to the atmosphere. See the illustration on the wikipedia page [0].

[0] https://en.wikipedia.org/wiki/Olfactory_bulb

The retina is basically an extension of the brain as well, no? If not, what is the key difference? Do you have a link talking about the atmosphere?

But the retina is not exposed to the outside world. It's got the rest of the eye between it and the air.

Ok, but is brain tissue uniquely infectable compared to eye tissue or something? The ultimate worry isn't that your olfactory bulb gets hurt, it's that the infection reaches deeper into the brain, and I don't get why it's easier to do that from the olfactory bulb rather than from the eye.

the conjunctiva of the eye is different tissue than optic nerve. there is fat, connective tissue, and muscle surrounding the eye.

When you have an infection around the nose area you'll be immediately put on strong antibiotics, because the danger of the infection spreading to the brain through the nose is so big.

https://en.wikipedia.org/wiki/Olfactory_bulb.

however:

Yan-Chao Li [etal.] ABSTRACT Swine hemagglutinating encephalomyelitis virus (HEV) has been shown to have a capability to propagate via neural circuits to the central nervous system after pe- ripheral inoculation, resulting in acute deadly encepha- lomyelitis in natural host piglets as well as in experimental younger rodents. This study has system- atically examined the assembly and dissemination of HEV 67N in the primary motor cortex of infected rats and provides additional evidence indicating that mem- branous-coating-mediated endo-/exocytosis can be used by HEV for its transsynaptic transfer. In addition, our results suggested that this transsynaptic pathway could adapted for larger granular materials, such as viruses. These findings should help in understanding the mechanisms underlying coronavirus infections as well as the intercellular exchanges occurring at the syn- aptic junctions. J. Comp. Neurol. 521:203–212, 2013.

https://doi.org/10.1002/cne.23171

it seems if you are not a swine or a rat you have little to worry about.

I don't understand what the Wikipedia link is supposed to show. Your eyes are tightly linked to your brain too.

the neuronal terminals leading to a lobe of the brain innervate the nasal mucosa.

the optic nerve is hidden behind the eye with a substantial barrier of non nervous tissue in front of it.

https://upload.wikimedia.org/wikipedia/commons/thumb/1/1e/Sc...

Can the infection move through nervous tissue more easily than non-nervous tissue?

that doesnt seem to be the case. this virus really likes your lungs because of a specific protien. this protien exists in your lungs at a greater concentration than elsewhere in your body. The virus would have to undergo a specific series of mutations to get good at targeting neurons.

yes, but there isn't a direct route from the outside to your brain. Your eye socket is relatively well insulated from the outside by skin, connective tissue, conjunctiva.

what you should take home from this is that you are not in immedate danger from a neurotrophic virus at this time.

what you should also take from this espescially if you are involved in policy is that this corona virus we are experiencing has in its distant heritage ancestors with reported neurotrophic properties. It is possible, that at some time in the future, this virus will accumulate signifigant genetic drift and gain or lose certain properties.