1.1.- How to measure Visual Acuity with the ETDRS?

Indepently you measure Far, Intermediate or Near vision the ETDRS procedure is the same:

  1. Read only one letter per row. For instance, first letter starting from the left or from the right and go down after each correct answer
  2. After the first failure, go to the previous line and ask for reading the five letters
  3. If you get ≥ 3/5 correct answers go down one row and ask again the five letters
  4. If you get <3/5 correct answers go up one row and ask again the five letters
  5. Visual acuity will be the last line for which the patient got ≥ 3/5 correct answers

Here you have an example. First you start reading only the first letter and going down up to the first wrong answer


As the first wrong answer was at 0.6 logMAR, I ask to the patient for reading the previous line of 0.7 logMAR

After asking for the five letters, the patient was right on three, therefore I ask for reading the complete next line of 0.6 logMAR

In the 0.6 logMAR line the patient got<3 correct answers, therefore the visual acuity of the patient was the last line on which three correct answers were obtained (0.7 logMAR)




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