Both a-waves, which represent photoreceptor function and b-waves, which are mediated by bipolar cells were measured in pAAV-hRKP-Tulp1 (without tracer AAV-RhoP-EGFP) treated Tulp1−/− eyes with MD and HD; uninjected wt and Tulp1−/− eyes were used as controls (Figure 4; n = 4–16). Here, TULP1 is linked to Huntington disease.