What is ETDRS?

ETDRS stands for Early Treatment of Diabetic Retinopathy Study. The first ETDRS trial was a multisite, randomized clinical trial designed to evaluate argon laser photocoagulation and aspirin treatment in the management of patients with early proliferative diabetic retinopathy. A total of 3,711 patients were recruited to be followed for a minimum of 4 years to provide long-term information on the risks and benefits of the treatments under study. Foregoing the traditional Snellen optotypes, which were at that time considered standard, better charts were needed for more accurate results. The ETDRS study introduced three new visual acuity charts, the “Original Series” with follow-up studies on those charts resulting in an additional “2000 Revised Series” which have a different letter arrangement for more homogeneous results. Both the original and revised series charts use Sloan letters. A variety of other optotypes are accepted worldwide. ETDRS equipment and testing have evolved into what is considered the gold standard of current-day clinical trials involving vision testing.