For comparison with the recent RNS - jCyte & Spark3 Oct 2019 23:55
jCyte's phase 1/2a RP study demonstrated a mean difference of 9 letters between the treated and untreated eye at 12 months at the highest dose.
At 9 months (and one patient) ReNeuron are at 13 letters [+ 12 (treated) to - 1 (untreated)].
jCyte reported 'no grade 4 events associated with the treatment', but didn't exclude grade 3 adverse events. For reference, grade 3 is severe, grade 4 is life-threatening.
It's also worth noting that there was a severe, i.e. grade 3, adverse effect in both Spark's Luxterna Phase I and Phase III trials, albeit with a larger population. Luxterna demonstrated a mean 8 letter improvement, averaged across both treated eyes, at 3 years.