ETDRS vision cha study is done in patients with diabetic retinopathy. ETDRS stands for:

D i.e. Early treatment for diabetic retinopathy study The ETDRS chaQ is similar to the LogMAR scale, and is used for early detection of diabetic retinopathy. And ETDRS stands for early treatment for diabetic retinopathy studyQ. The visual acuity in adults is usually measured by: Snellen's Fraction (in Metres): As 6/6, 6/9, 6/12, 6/18, 6/24, 6/36, 6/60... depending on the no. of lines that the patient could read at 1m. Each alphabet subtends an angle of 5min at the nodal point at respective distance. Snellen's Fraction (in Feet): The same as above, only that in the US its conveed to feet, so recorded as 20/20, 20/200... Decimal Acuity: Snellen's fraction is reduced to a decimal no. and a higher acuity is represented by a larger no., which is reverse in Snellen's grading. LogMAR Scale Q: Based on the Minimum Angle of resolution. Here each row has 5 alphabets each in a ratio of 5:4, with each row in geometric progression i.e. each subsequent row has alphabets smaller in size by a factor of Logio10. ETDRS Q: Similar to LogMAR, having 10 alphabets in ratio 5:5.