Does continued diabetes treatment worsen eye damage?

This study evaluated the progression of diabetic retinopathy or DR (damage to the eye caused by high blood sugar levels) with continuing use of exenatide (Byetta) therapy and to establish if the worsening of DR was temporary.

Diabetes mellitus (DM) is a metabolic disease in which a person has abnormally high blood sugar, either because the pancreas does not produce enough insulin, or because cells do not respond to the action of insulin. Blood sugar control in DM patients can be measured through the glycated hemoglobin or HbA1c (a test that shown an average of blood sugar levels in the previous 2 to 3 months). Diabetic retinopathy (DR) is one of the main complications of DM, which can lead to blindness. Studies have shown that a rapid improvement in blood sugar levels can worsen DR. DM therapy with exenatide, a drug that increases the release of insulin by the pancreas, produces a significant and sustained reduction of blood sugar levels and in HbA1c. However, there is no data available about the effect of continued exenatide therapy on DR progression and whether this condition is temporary. 

This is the second phase of a study that showed that from 165 patients treated for 10 months with exenatide, 30% had DR progression with HbA1c improvement. This part of the study reviewed the data from 39 patients who had a reduction in HbA1c levels and progression of DR in the first phase of the study and continued exenatide therapy afterwards. These patients were followed up for approximately 439 days after the first part of the study.

Results show that 62% of patients had an improvement in DR while 18% reported no change. From these patients, more than 74% had HbA1c increase, an effect that is known for prolonged exenatide treatment. The risk factors for DR progression in this study were the duration of diabetes and the severity of DR at the beginning of the treatment. 

In conclusion, this study demonstrates that exenatide therapy is associated with temporary worsening of DR. While 30% of the patients may develop or worsen DR with improvement in blood sugar levels, 80% of the patients who continue the therapy have a DR improvement. 

This study included a very small number of patients. Larger studies are needed to confirm these results.

Programs for DR screening should be developed for patients with diabetes. Also the development of new DR or worsening of pre-existing one should not stop doctors from trying to achieve normal blood sugar levels in their patients.