Construction and validation of a Tamil logMAR chart.
OBJECTIVE
To design, construct and validate a new Tamil logMAR visual acuity chart based on current recommendations.


METHODS
Ten Tamil letters of equal legibility were identified experimentally and were used in the chart. Two charts, one internally illuminated and one externally illuminated, were constructed for testing at 4 m distance. The repeatability of the two charts was tested. For validation, the two charts were compared with a standard English logMAR chart (ETDRS).


RESULTS
When compared to the ETDRS chart, a difference of 0.06 +/- 0.07 and 0.07 +/- 0.07 logMAR was found for the internally and externally illuminated charts respectively. Limits of agreement between the internally illuminated Tamil logMAR chart and ETDRS chart were found to be (-0.08, 0.19), and (-0.07, 0.20) for the externally illuminated chart. The test - retest results showed a difference of 0.02 +/- 0.04 and 0.02 +/- 0.06 logMAR for the internally and externally illuminated charts respectively. Limits of agreement for repeated measurements for the internally illuminated Tamil logMAR chart were found to be (-0.06, 0.10), and (-0.10, 0.14) for the externally illuminated chart.


CONCLUSIONS
The newly constructed Tamil logMAR charts have good repeatability. The difference in visual acuity scores between the newly constructed Tamil logMAR chart and the standard English logMAR chart was within acceptable limits. This new chart can be used for measuring visual acuity in the literate Tamil population.
Varadharajan
Srinivasa
S
Elite School of Optometry, Unit of Medical Research Foundation, St Thomas Mount, Chennai 600 016, India. drlsv@snmail.org
Srinivasan
Krithica
K
Kumaresan
Brindha
B
D000293:Adolescent; D006801:Humans; D007194:India; D017410:Practice Guidelines as Topic / Q000592:standards; D015203:Reproducibility of Results; D014786:Vision Disorders / Q000175:diagnosis*; D014787:Vision Tests / Q000295:instrumentation* / Q000379:methods; D014792:Visual Acuity / Q000502:physiology; D055815:Young Adult