[Preproliferative diabetic retinopathy sub-classification 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) in cases of mild preproliferative diabetic retinopathy(PPDR).

Materials And Methods: We evaluated the relationship between the mean hemoglobin A1C (HbA1C) value during a period of at least 2 years and the proportion of patients developing PDR in cases of mild PPDR, based on our previously proposed subclassification.

Results: During follow-up, 27% of all cases developed PDR. The mean HbA1C value in these cases was 9.4%, which was significantly higher than the 7.6% in cases which had not developed PDR. The proportion of patients developing PDR was 48% in cases with a mean HbA1C value 8.6% or more. In contrast, the proportion was 8% in cases with a mean HbA1C value below 8.6%. It was estimated that the proportion of patients developing PDR will approximately double if the mean HbA1C value increases by one percent. The cumulative occurrence rates of PDR at two, 5, and 10 years were estimated to be 5, 28, and 60% in cases with a mean HbA1C value 8.6% or more and 0, 7, and 10% in cases with a mean HbA1C value below 8.6%, respectively.

Conclusion: Based on the above results, we conclude that more strict systemic and ophthalmological control is indicated for patients with a mean HbA1C value exceeding 8.6%.