For each subject, a single examiner performed VA determination
with both the standard and ETDRS-Fast methods in two separate sessions,
to assess the validity of the fast method compared with the standard
one and the reproducibility of both procedures. The method to be used
first was randomly assigned, and the order was reversed between the
first and the second sessions, to avoid having any learning effect act
preferentially on one procedure. The first and second sessions were at
least 1 hour, but not more than 24 hours, apart. Within each session,
VA assessment with one method was performed approximately 10 minutes
after VA assessment with the other method, with the subject exiting the
examination room between assessments. To minimize a possible
intrasession learning effect, the VA determination on the study eye
(right, with ETDRS chart 1) was followed by determination of VA on the
fellow eye with chart 2. To further reduce a possible bias toward
achieving agreement between the ETDRS-Fast and standard measurements,
the score sheet from a previous test of a given patient was never
available to the examiner performing a new VA measurement. Test
duration was recorded to verify whether there was a significant
difference between standard and ETDRS-Fast procedures.