Effect of Captopril on Aqueous Levels of Angiotensin II and Its Correlation with Macular Edema in Diabetic Patients

To determine whether angiotensin II (AT II) levels in aqueous humor are related to diabetes mellitus and to evaluate the effect of captopril on this level. We also evaluated the correlation between severity of macular edema and captopril use. In a case-control study, aqueous humor samples were obtained at the onset of cataract surgery from 58 eyes of 58 patients, of whom 37 were diabetic. From these latter subjects, 16 had taken captopril (captopril group) for at least six months and 21 had not taken any angiotensin converting enzyme inhibitor (non-captopril group). AT II level was assessed by radioimmunoassay. Severity of macular edema was evaluated by clinical examination after surgery. The aqueous level of AT II was significantly higher in diabetic patients (31.0±7.3 pg/ml) compared to non-diabetics (6.28±2.8 pg/ml) (Mann Whitney U test, P < 0.0001). In diabetic patients, aqueous concentration of AT II in the captopril group (16.3±6.5 mg/ml) was significantly lower than the non-captopril group (75.73±9.36 mg/ml) (Mann Whitney U test, P < 0.0003). The severity of macular edema was significantly less in the captopril group compared to the non-captopril group: 68.75% of the captopril group vs 33.3% of the non-captopril group had no macular edema (P < 0.005). These findings suggest that the aqueous level of AT II is higher in diabetic eyes and is correlated with the severity of diabetic macular edema. Considering the possible role of AT II in the pathogenesis of diabetic macular edema, modulation of the ocular renin-angiotensin system may become an important target for its treatment.