Table of Contents

## What is logMAR visual acuity?

Abstract. Background: Visual acuity, increasingly measured using a logarithm of the minimum angle of resolution (logMAR) chart, is the “gold standard” by which the outcomes of the vast majority of clinical trials or interventions are judged.

**How do you convert visual acuity to logMAR?**

Decimal scores were converted to logMAR using the formula logMAR = -log(decimal acuity).

**What is the difference between logMAR and Snellen?**

In Snellen notation, 20/20 vision corresponds to logMAR = 0 and the MAR is equal to 1.0 arc minute. The MAR, in arc minutes, is equal to the inverse of the Snellen fraction. As acuity improves better than 20/20, the logMAR score will have an increasing negative sign value.

### How does logMAR record visual acuity?

The logMAR VA can be calculated as 0.1 (8) + (2) (0.02) = 0.84 logMAR. The formula: logMAR score (0.1 NL + 0.02 nl) where NL = number of lines completely read and nl = number of additional letters read ap- plies. For this method, the higher the logMAR VA score, the better the visual acuity.

**How is logMAR calculated?**

The logMAR scale is calculated as log (MAR) = log (1/V) = – log (V). LogMAR notation is widely used in scientific publications. Note that it is a scale of vision loss, since higher values indicate poorer vision. The value “0” indicates “no loss”, that is visual acuity equal to the reference standard (1.0, 20/20).

**How do you use logMAR?**

- Ask patient to read down chart with one eye covered.
- Note how many letters are read correctly until none of the letters on a line are.
- read correctly.
- Read off vision score from chart.
- Repeat with pinhole if the vision is worse than 0.2.
- If logMAR vision is worse than 1.0, retest at 2m or 1m (see over page)

## What is logMAR value?

Each letter has a score value of 0.02 log units. Since there are 5 letters per line, the total score for a line on the LogMAR chart represents a change of 0.1 log units. The formula used in calculating the score is: LogMAR VA = 0.1 + LogMAR value of the best line read – 0.02 X (number of optotypes read)

**What is the purpose of the logMAR chart?**

A logMAR chart (Logarithm of the Minimum Angle of Resolution) is a chart consisting of rows of letters that is used by ophthalmologists, orthoptists, optometrists, and vision scientists to estimate visual acuity.

**How is visual acuity scored on a LogMAR chart?**

When using a LogMAR chart, visual acuity is scored with reference to the logarithm of the minimum angle of resolution, as the chart’s name suggests.

### What is the difference between LogMAR and low vision?

However, LogMAR is actually a notation of vision loss. The World Health Organization established criteria for low vision using the LogMAR scale. Low vision is defined as a best-corrected visual acuity worse than 0.5 LogMAR but equal or better than 1.3 LogMAR in the better eye.

**What is a LogMAR chart?**

A LogMAR chart comprises rows of letters and is used by ophthalmologists, optometrists and vision scientists to estimate visual acuity.

**What is the logarithm of reduced acuity?**

An observer who can resolve details as small as 1 minute of visual angle scores LogMAR 0, since the base-10 logarithm of 1 is 0; an observer who can resolve details as small as 2 minutes of visual angle (i.e., reduced acuity) scores LogMAR 0.3, since the base-10 logarithm of 2 is 0.3; and so on.