A large-scale study uncovered greater possible risk of diabetic macular edema in patients taking thiazolidinediones like pioglitazone (Actos) and rosiglitazone (Advania) to treat Type 2 diabetes – a condition that can already cause blindness.
 
According to MedicineNet, diabetic macular edema occurs in people with type 2 diabetes when fluid from blood vessels escapes within the macula and causes the retina to swell. The macula is a small section of the retina that is vital to daytime vision because of its high concentration of specialized nerve endings called cones.
 
After one year of use, diabetic macular edema was present in 1. 3 percent of patients taking thiazolidinediones, compared to 0.2 percent in patients not taking the drugs, according to study author Dr. Iskander Idris of Sherwood Forest Hospitals Foundation Trust in Nottingham, England. The analysis was adjusted to account for other possible contributing factors like age, blood pressure and the use additional anti-diabetic or cardiovascular drugs, but the chance of developing diabetic macular edema while on thiazolidinediones remained 2.3 times higher from after one year to 10 years of use.
 
Idris and his colleagues also found that injecting insulin while taking thiazolidinediones appeared to increase the risk of getting diabetic macular degeneration, while the use of aspirin and ACE-inhibitors appeared to reduce the chance of developing diabetic macular edema. According to WebMD, aspirin is used to reduce blood clots that can cause strokes or heart attacks, and ACE-inhibitors are used to lower blood pressure.
 
The observational study, published in The Archive of Internal Medicine, examined 103,368 subjects with type 2 diabetes who reported no history of visual problems, but it was not the only study to report the visual complications in patients on thiazolidinediones. A U.S. study published in the American Journal of Opthalmology examined 996 diabetic macular edema patients and revealed that those taking thiazolidinediones were 2.6 times more likely to develop diabetic macular edema than nonusers.
 
Thiazolidinediones, according to WebMD, are a class of drugs that work by increasing the body’s sensitivity to insulin by lowering insulin resistance, and are prescribed for patients with type 2 diabetes who have failed to lower blood sugar levels on other anti-diabetic medications.
 
Type 2 diabetes develops when a person’s body does not produce enough insulin or does not process the insulin so that the necessary glucose is transferred to cells. The American Diabetes Association says that diabetics are 40 percent more likely to develop glaucoma and 60 percent more likely to develop cataracts than other people.
 
Since diabetics are already prone to vision problems, careful consideration should go into prescribing thiazolidinediones to patients who did not respond to other anti-diabetic drugs.