mm (be precise)
? options

? r/l filters
? shortcuts


Very quick guide: Calibrate and configure your chart using the Settings form and consult this help guide if you get stuck. You will need a measuring tape to measure viewing distance and a ruler to measure the calibration line.
Charts are in 4 categories; V for VA, R for Refraction, B for Binocular and M for Miscellaneous. Use the onscreen arrows or arrows on your keyboard to navigate horizontally between categories and vertically within categories. Alternatively, the category buttons in the flyout at bottom right give you one-click access to your most-used chart in that category. These category links are also mapped to the corresponding letters on your keyboard.
Click or tap on any line label to mask that line. Click or tap again to unmask.
Click or tap on any letter to mask it. Click or tap on it again to mask a column of letters. Click or tap on any letter in the column to show all again.
If there is a round button in the sidebar below the navigation arrows, the chart has a function mapped to the spacebar, such as zoom or rotate. You can also activate the function by clicking on or tapping the chart itself or the button.
Why is one of the charts just black?
So you can darken your room with one click.

The optotypes fields allow you to select the symbols to be displayed. You cannot change the array nor order of the lines displayed here.
  • Optotype: Select from a range of standard optotypes.
  • Alphabet: The available options are dependent on the OPTOTYPE selected above. SnellenU and SloanU use a wider selection of letters, but letters may not be of equal readability. BS4724.3 and ETDRS are standard alphabets using fewer letters, but with more equal readability. Letters can be shuffled to prevent learning and increase repeatability - see below
  • Notation: Sets the notation type on the VA label on each chart line. Regardless of notation or optotype, WolfChart uses the standard logMAR array of subtenses (0.501", 0.631", 0.794", 1", 1.259", 1.585", 2", 2.512", 3.162", 3.981", 5.012", 6.31", 7.943", 10") with each 3 lines doubling the subtense. Notation and Numerator express these subtenses as your preferred VA value. "Metres" is standard Snellen notation eg. 6/6; "Feet" is the imperialist equivalent eg. 20/20; DecimalV is a the European standard (EN ISO 8596) eg. 6/60 = 0.1, 6/12 = 0.5; logMAR is explained here
  • Numerator: Sets the numerator of the fraction notation types only; if Notation is set to logMar or DecimalV, this setting makes no difference.
    "Standard" is either 6 or 20 depending whether Notation is set to Metres or Feet above. VA labels will display as either 6/ or 20/ regardless of the value in Distance.
    "Actual" is the value entered in Distance (see below) rounded to the nearest 0.1m or 0.5ft, and VA labels will show this rounded numerator, with a ! instead of a /, and a proportionally adjusted denominator. Please note that it is not advisable to use Standard if the Distance varies a large amount from 6000mm, say outside 5500-6500mm. The numerator should be the tested distance or near to it.

The two CALIBRATION values are the only values that influence the size of the letters. The RECORDING values above only change the VA labels on the letter chart lines, and have no bearing on the letters themselves.

  • Distance: Enter the distance from the patient's eye to the letter chart in mm. Eg 6m is 6000mm. Even if you work in feet (see Notation above), you must enter the Distance in mm. If using a mirror to double the test distance, measure BOTH from the patient's eye to the mirror AND from the mirror to the display and ADD the two distances (and don't forget to check the Mirrored/Direct setting - see below). If you are using Notation value of "Feet", Numerator will be converted to the nearest foot, or to 20 depending on the value in Numerator.
  • Length of the line below: Calibrates the chart. WolfChart does not need to know anything about the screen you are using; it just needs the length of this green line as it is displayed. Measure the length of the green line as accurately as possible. On a touch screen this is tricky, but you'll work it out. You will need to re-check this value if you change display hardware, graphics adapter settings, or if you turn your display from landscape to portrait or vice versa. Take particular care here if you are using extended display from a computer as pixel density may be different between the computer screen and the external display.
  • Sort: Unless the display is very large (about 1m wide by about 1.5m tall viewed at 6m), the letter chart will display in pages - see SHORTCUTS below. Here you can select whether to display the page of the smallest or largest lines first. If French, you have a Monoyer option.
  • Mirrored/Direct: Select "Direct" if WolfChart is to be viewed directly, otherwise select "Mirrored" and the letters and lines will be reversed, but the labels not. If changing this setting, don't forget to set the Distance (see above) accordingly.
  • Optotype colour: Defaults to solid black. Enter any valid rgba string or use the preset buttons for common values.
  • Background colour: Defaults to solid white. Enter any valid rgba string or use the preset button/s. If a Vanishing optotype is selected, this field is disabled.
WolfChart uses red and green targets for binocular dissociation tests. The default hues may work fine for your filters, but if not, you can set the hues using the sliders. The objective is for each slider to be only visible from one eye using red/green or red/blue goggles or trial set filters. Sometimes you can't get total invisibility, or there are two invisible settings. In either case the tests will work if you can make the two hues as different as possible when viewed through each coloured filter.

Use these fields to specify keyboard shortcuts for operating WolfChart. Certain keys eg. v, r, b and m are reserved and you will be alerted not to use them if you try.

  • Page Up/Dn/Left/Right: Page Up, Down, Left and Right are already mapped to the arrows on your keyboard, and the arrow buttons on screen. If your controller doesn't have arrow keys, add custom shortcuts here, eg u,n,g and k respectively
  • Shuffle:: Toggles shuffle of the letters. Each shuffle is random, but each unshuffle returns the alphabet to it's original order.
  • Duochrome:: Toggles a red/green background on V charts.