Acuity Charts

The labels displayed to the left and right of each row of letters of the LogMAR, Snellen and Single letter charts may be shown in a variety of formats.  The format can be set from the Acuity charts tab of the Program Options window as shown below.

Snellen (m): The format favoured in the UK where VA is expressed as a function of a viewing distance of 6 metres.

Snellen (ft): The format favoured in the US where VA is expressed as a function of a  viewing distance of 20 feet.

Snellen decimal: The format favoured in much of Europe where VA is expressed as a Snellen decimal, e.g. 6/6=1, 6/12=0.5 etc.

LogMAR: LogMAR stands for the Log of the Minimum Angle of Resolution (MAR). The MAR is taken as the angle subtended by the gap between the limbs of a letter which is one fifth of the vertical angle subtended by the letter.

VAR (Visual Acuity Rating): The VAR score provides a much simpler method for scoring logMAR charts. The 0.00 (6/6) row is given a score of 100 and each letter has a score of 1.  

No. Letters : Some clinics have adopted a methodology where the number of letters read by the patient from a starting LogMAR row is recorded (usually the top row on a fixed back-illuminated chart).  Unfortunately the starting LogMAR row used is not standardised resulting in differences between clinics.  Test Chart 2016 allows the user to specify the starting LogMAR row to provide continuity with an existing scoring system.

None:  No label is displayed.

The Font size of the labels can also be specified on this tab.  The optimum font size will depend on screen size and the distance that the practitioner views the chart from.

Five different sets of letters/optotypes can be defined for each optotype by clicking on Optotypes Sets.