Associations Between Initial Glycated Hemoglobin at Diabetes Diagnosis, Longitudinal Changes and Medication Effects, and the Severity and Progression of Sight‐Threatening Diabetic Retinopathy

Diabetic retinopathy (DR) is a leading cause of vision impairment in patients diagnosed with Type 2 diabetes mellitus (T2DM). Awareness of risk factors is necessary to reduce or prevent harmful effects of DR such as irreversible vision loss, and to help ensure early treatment. This study aimed to evaluate associations between initial HbA1c at diabetes diagnosis, longitudinal changes, and medication adherence (MR), and the severity and progression of sight-threatening diabetic retinopathy (STDR). From July 2022 to January 2024, 300 patients with T2DM aged ≥ 20 years were recruited, and the data of 178 patients with complete data were analyzed, focusing on initial HbA1c levels at DM diagnosis, subsequent HbA1c changes at ophthalmologic visits, and MR using the Taiwanese version of the Morisky Medication Adherence Scale-8 (MMAS-8). Patients with persistently high or fluctuating HbA1c levels had a higher risk of severe DR compared to those with consistently low HbA1c. High initial HbA1c was more strongly associated with DR severity in females, patients aged < 65 years, and those without diet or exercise control. Poor or moderate MR was associated with higher HbA1c at follow-up and increased STDR risk. In contrast, patients aged ≥ 65 years were less likely to develop severe DR. Findings of this study accentuate the importance of initial glycemic control and HbA1c trends during ophthalmologic care in managing DR progression, suggesting that patients with high initial HbA1c may benefit from closer early ophthalmic monitoring.