What is logMAR vision?
Table of Contents
What is logMAR vision?
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.
Is logMAR more accurate than Snellen?
The average difference between Snellen and ETDRS charts for all tested eyes was 0.13 ± 0.18 logMAR or 6.5 letters better on the ETDRS chart at 4 meters (P = . 000000001) and 0.16 ± 0.18 logMAR or 8 letters better on the ETDRS chart at 2 meters (P = . 000000001).
What is logMAR in Snellen?
Initially conversion is not always intuitive as poorer vision is recorded as a higher number eg 6/60 Snellen is 1.00 LogMAR and 6/6 Snellen is 0.00 LogMAR. This table may help to assist and to ease the understanding of visual acuity measurements.
What does logMAR 0.2 mean?
To calculate the score, take the row number where they got all four correct (0.3), count the number of letters below that that they got correct (4) and multiply this by 0.025 = 0.10. This is then subtracted from 0.23 to give the LogMAR score of 0.20.
What is a normal logMAR?
Normal (6/6 or 20/20) vision equates to 0.0LogMAR (see conversion table below). There are two types of visual acuity. 1. Threshold visual acuity. Meaning a measure of the smallest black / white detail that can be seen.
How do you do logMAR vision?
- 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)
How do you read logMAR?
How do you convert visual acuity to logMAR?
Conversion
- logMAR to ETDRS: logMAR rounded to the first digit and converted with the chart.
- Snellen to logMAR: logMAR = -1 * log10(snellen_frac)
- Snellen to ETDRS: ETDRS = 85 + 50 * log10(snellen_frac) Gregori et al..
- ETDRS to logMAR: logMAR = -0.02 * etdrs + 1.7 Beck et al.
What is a normal LogMAR?
What is the principle of LogMAR chart?
Acuity charts that follow the principle of logarithmic size progression (logMAR charts) are considered to be the gold standard for the assessment of distant vision. But it is not well accepted for routine eye examinations due to increased testing time and the complexity of scoring.
What is 6.5 Snellen chart?
Normal visual acuity is called 6/6, which means that from 6 metres away (the first number) you can read all 6 lines of the chart.
How do you convert decimal to logMAR?
Decimal scores were converted to logMAR using the formula logMAR = -log(decimal acuity).
How do you calculate logMAR to Snellen?
The formula: logMAR acuity = x – 0.02y, where x is the logMAR value of line completely read by the subject and y is the number of letters read in the low- er row. Applying this method to the example above (Snellen acuity 6/12+2), the logMAR value of the let- ters read is: 0.3 – 0.02 (2) = 0.26.
How do I change from Snellen to logMAR?
How do you calculate logMAR 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.
