A logMAR chart is a chart consisting of rows of letters that is used by ophthalmologists, orthoptists, optometrists, and vision scientists to estimate visual acuity. The name of the chart is an abbreviation for "logarithm of the Minimum Angle of Resolution".

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LogMAR VA charts are considered nowadays the gold standard for VA 1 in both clinical and research settings, 11 and should therefore be adopted in all clinical settings for vision care. Why then has logMAR VA charts not yet been universally adopted?

The term LogMAR is an acronym for the Logarithm of the Minimum Angle of Resolution. LogMAR charts have a number of advantages over Snellen charts and have become the gold standard method for assessing visual acuity.

The value for the lowest line where all the letters can be read is noted. The number of letters read on the line below is then multiplied by 0.02 and subtracted from this value. This is the logMAR acuity. For example if all the letters on the 0.5 line and two letters on the 0.4 line are read, the logMAR acuity will be 0.5 – 0.04, i.e. 0.46.

Convert between Snellen and logMAR visual acuity measurements.

However, the processes involved in the use of this logMAR principle require series of multiplication and division by the logMAR ratio of 1.2589. A table computed and pre-sented in this article provides easy reference for the conversions and predictions needed for the various quantities at near.

All charts have been designed according to the logMAR principles proposed by Bailey and Lovie 1 that are currently accepted worldwide as the gold standard for visual acuity measurement. According to logMAR design, all charts have the following characteristics:

Snellen and LogMAR acuity testing 1 The Snellen Chart (fig 1), which traditionally has been used to measure visual acuity is easily recognised as one of the hallmarks of the ophthalmologists consulting room.