It doesn't have a strong impact, and the design also doesn't prevent good night vision (the basic structure of a cats eye is similiar, ALL chordata have an inverted neural makeup).

But that doesn't mean the setup makes sense, and that is exactly my point.

And long term, this has an impact. For example, vertebrate brain size is limited by the simple factor, that we have to put all the connections on the outside. The more neuronal bodies we have, the more connections they require.

    N <---> N

In this clumsy diagram, 2 neurons talk with the connections on the inside. However, vertebrate brains have to do this instead:

    +--------------+
    |              |
    +-> N      N <-+

It's easy to see how the second setup becomes prohibitive when more Neurons are added to it. The brains of Protostomia again don't have that problem...they can have the connections on the inside, and the neuron bodies on the outside, aka. the logical setup.

Now there are ways around that, eg. Reptile and Bird brains grow in bulbs that theoretically allow sustained growth without the connective layer getting in the way. But similar to the reflective layer in our eyes, this is not a setup that's there because it makes a lot of sense...it's a hack, a workaround for some "legacy system", that is now so enmeshed, it's impossible to change.