TZDs can decrease plasma glucose in type 2 diabetic patients, but the major side effects are able to cause fluid retention. This prospective study will be able to test whether thiozolidinediones causes macular edema and to evaluate whether thiozolidinediones delays onset of diabetic retinopathy. The investigators also will be able to find the changes in the level of urinary albumin-to-creatinine ratio, circulating metabolic parameters and adipocytokines between the treatment of TZDs and Acrbose. The investigators can compare the time from the base-line visit to the first detection of overt nephropathy, the time to the first event of the composite end point of the time from the base-line visit to a doubling of the serum creatinine concentration, end-stage renal disease, or death.