Visual Nonspecific Clinical Trial
Official title:
Repeatability and Concordance of Visual Acuity Level Measured With ETDRS Numeric Charts, ETDRS Landolt C Charts, and Original ETDRS Letter Visual Acuity Charts in Thai Individuals
This is a cross-sectional study to determine the repeatability and concordance of visual acuity level measured with the original ETDRS letter, ETDRS Landolt C, and ETDRS numeric chart in Thai individuals.
The ETDRS visual acuity chart has been used as a standard visual acuity measurement chart in
ophthalmic clinical trials due to its proven high repeatability comparing to other visual
acuity chart. However, the original ETDRS alphabet chart could not be used in every
individual around the world, especially those who are non-english speakers. Landolt C chart
has been a recommended chart to test visual acuity in those living in a country where
English is not a common language, however, some difficulties including right-left confusion
occurred when testing with the Landolt C chart, leading to the unreliable results of visual
acuity measurement using the Landolt C chart. Recently, the ETDRS numeric chart was
introduced by some medical equipment companies but there is limited information regarding
the repeatability and concordance of the new ETDRS numeric chart comparing to the original
ETDRS alphabet and Landolt C chart.
Therefore, this study aims to determine the repeatability and concordance of visual acuity
level measured with the original ETDRS alphabet, the ETDRS Landolt C, and the ETDRS numeric
chart. Results from this study would be able to suggest an appropriate ETDRS chart to be
used in clinical studies in Thailand or other countries where English is not the native
language.
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Observational Model: Case-Only, Time Perspective: Cross-Sectional