I'm sorry to hear about your condition, but am glad you're taking the initiative to experiment with new treatment options.

I have a severe visual impairment due to a genetic condition, diagnosed as OPA1, which resulted in degeneration of my optic nerve and macula due to mitochondrial dysfunction from a very young age.

I started researching tDCS for vision loss about a year ago, and came across the treatment you linked to in Germany with tACS. I tried tDCS as I didn't have time or resources to go to Germany for that treatment. I used tDCS in conjunction with a vision training iPad app called Ultimeyes, with good results to my contrast perception and visual function.

As my condition doesn't effect my visual field, I couldn't say whether or not it had an effect on this, but it maybe worth a try. I've also started looking into LLLT as a way to increase cellular respiration in the retina and visual cortex. Anodal tDCS and LLLT both seem to positively influence cellular respiration and blood flow.

From what I understand, tACS has more to do with synchronization of firing patterns of neurons, whereas tDCS has more to do with up/down regulation of neurons directly under the sites of stimulation, as well as effecting the pathways between the electrodes. It's still unclear from a research perspective what this means in practice, but my guess is that the current is reinforcing the connections between the targeted regions, and when combined with deliberate cognitive activity, may help to increase the capacity of those pathways.

I'd be interested to try tACS myself, but at this time there aren't any suitable devices that have this capability available on the market today, and I don't have the technical skills to build a device myself.

I also found it useful to add nutritional supplements as an adjunctive treatment. I take DHA, combined with citicoline and uridine, as well as royal jelly, and short runs of centrophenoxine.

I hope this is helpful. :)