Construction and validation of a Tamil logMAR chart.

Area of Science:

• Ophthalmology
• Optometry
• Vision Science

Background:

• Accurate visual acuity measurement is crucial for eye care.
• Standardized charts like the ETDRS chart are widely used.
• A need exists for culturally relevant visual acuity charts in different languages.

Purpose of the Study:

• To design, construct, and validate a new Tamil logMAR visual acuity chart.
• To ensure the chart adheres to current international recommendations for visual acuity testing.
• To provide a reliable tool for assessing vision in the Tamil-speaking population.

Main Methods:

• Experimentally identified ten Tamil letters of equal legibility for chart construction.
• Developed two versions: internally and externally illuminated charts, tested at 4 meters.
• Assessed chart repeatability and validated against the standard English logMAR (ETDRS) chart.

Main Results:

• The Tamil logMAR charts showed good repeatability with minimal test-retest differences (0.02 +/- 0.04 logMAR).
• Differences compared to the ETDRS chart were within acceptable limits (0.06-0.07 logMAR).
• Limits of agreement indicated good consistency between the new Tamil charts and the standard ETDRS chart.

Conclusions:

• The newly developed Tamil logMAR charts exhibit strong repeatability.
• The visual acuity scores obtained using the Tamil charts are comparable to the standard English ETDRS chart.
• This validated Tamil logMAR chart is suitable for measuring visual acuity in literate Tamil speakers.