CA1 and diabetic retinopathy: Nonetheless, high levels of BK may be found in the eye under conditions of diabetic retinopathy, when the levels of carbonic anhydrase I, an enzyme responsible for generating BK (Han et al., 2002; Gao et al., 2007), are ~15- and ~8-times higher than in non-diabetic patients and in patients with diabetes without retinopathy, respectively (Gao et al., 2007).