Subclassification of preproliferative diabetic retinopathy and glycemic control: relationship between mean hemoglobin A1C value and development of proliferative diabetic retinopathy.

PURPOSE We evaluated the relationship between long-term glycemic control and the proportion of patients developing proliferative diabetic retinopathy (PDR) among cases with mild type preproliferative diabetic retinopathy (PPDR). METHODS The relationship was evaluated between the mean hemoglobin A1C (HbA1C) value during a period of at least 2 years and the proportion of patients developing PDR among cases with mild type PPDR, based on our previously proposed subclassification. RESULTS During follow-up, 27% of the total PPDR cases developed PDR. The mean HbA1C value in those patients who had developed PDR was 9.4% and was significantly higher than the 7.6% in those who had not developed PDR. The proportion developing PDR was 48% of the cases with a mean HbA1C value of 8.6% or more. By comparison, the proportion developing PDR was 8% among those with a mean HbA1C value below 8.6%. The proportion developing PDR was estimated to approximately double with each 1% increase in the mean HbA1C value. The cumulative occurrence rates of PDR at 2, 5, and 10 years were estimated to be 5%, 28%, and 60% in cases with a mean HbA1C value of 8.6% or more, and 0%, 7%, and 14% in those with a mean HbA1C value below 8.6%, respectively. CONCLUSION Stricter systemic and ophthalmological control is indicated for cases with a mean HbA1C value exceeding 8.6%.