Visual function was assessed with electroretinography (ERG) performed at pretreatment as baseline, 1 month after AAV1-Rz-SOD2 injection, and 4 months after AAV1-Rz-SOD2 injection as previously described [33 (link)]. For the ERGs, the mice were dark-adapted overnight, and full-field ERGs were recorded with a visual electrodiagnostic system (UTAS-E 2000; LKC Technologies, Gaithersburg, MD) using gold wire loop electrodes placed on each cornea and a reference electrode placed subcutaneously between the eyes. Scotopic rod recordings were performed with stimuli presented at intensities of 0.025, 0.25, and 2.5 log cd-s/m2 at 10-, 20-, and 30-s intervals, respectively. Ten responses were recorded and averaged at each light intensity. Photopic cone recordings were performed after the mice were light adapted to a white background light of 100 cds/m2 for 5 min. Recordings were performed with four-increasing flash intensities from 0, 5, 10, and 25 log cd-s/m2 in the presence of a constant 100 mcds/m2 rod suppressing background light. Fifty responses were recorded and averaged at each intensity. The a-waves were measured from the baseline to the peak in the negative direction, and the b-waves were measured from the negative peak to the major positive peak. The ERG data are presented as comparisons between treatment conditions for the mean of the maxima for a- and b-wave responses.