Resource Categories

Featured Post
#Visual Acuity
December 6, 2021

What is Visual Acuity?

Visual acuity refers to the clarity or clearness of the vision, a measure of how well a person sees. The ...

EyeOnVision December, 2021 – ETDRS


Understanding 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.


Precision Vision has been involved in planning some of the most integrated international trials with most of the industry’s leading pharmaceutical companies.
101,000 Precision Vision charts and 31,000 Precision Vision Illuminator Cabinets and accessories have been distributed worldwide throughout the last decade alone!


Q: How do you test and score ETDRS Charts?

A: Scoring in ETDRS is typically done by letter count.  Visual Acuity Score ( VAS ) awards one point for every letter correctly guessed.  Click read more below to continue reading or request additional information!