For testing vision it is mandatory to switch off auto-brightness in order to maintain the background luminance constant for any environmental light used. The screen brightness can change if you put an App in second plane or if you put the iPad in the sleep mode. This can result in testing vision in different conditions of background brightness. However, from version 2.0 VisionC automatically detects when screen brightness has changed and modifies the brackground brightness to the stored in the App each time that you use the App for testing vision.

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ETDRS Chart for iPad (VisionC) (qvisionacademy.com)

Indepently you measure Far, Intermediate or Near vision the ETDRS procedure is the same:

1. Read only one letter per row. For instance, first letter starting from the left or from the right and go down after each correct answer
2. After the first failure, go to the previous line and ask for reading the five letters
3. If you get ≥ 3/5 correct answers go down one row and ask again the five letters
4. If you get <3/5 correct answers go up one row and ask again the five letters
5. Visual acuity will be the last line for which the patient got ≥ 3/5 correct answers

Here you have an example. First you start reading only the first letter and going down up to the first wrong answer

As the first wrong answer was at 0.6 logMAR, I ask to the patient for reading the previous line of 0.7 logMAR

After asking for the five letters, the patient was right on three, therefore I ask for reading the complete next line of 0.6 logMAR

In the 0.6 logMAR line the patient got<3 correct answers, therefore the visual acuity of the patient was the last line on which three correct answers were obtained (0.7 logMAR)

Select the presentation distance in the FAR picker -> Press Go below Far-> Confirm

To measure far distance visual acuity you have first to select the distance in the FAR picker view, then put the iPad at the selected distance from the eyes and start to measure with the ETDRS. A confirmation message will appear, please ensure that the iPad is at the distance figured at the confirmation message. The last selected distance will appear when you restart the App.

Select the presentation distance in the INTERMEDIATE picker -> Press Go below Intermediate -> Confirm

To measure intermediate visual acuity you have first to select the distance in the INTERMEDIATE picker view, then put the iPad at the selected distance from the eyes and start to measure with the ETDRS. A confirmation message will appear, please ensure that the iPad is at the distance figured at the confirmation message. The last selected distance will appear when you restart the App.

Select the presentation distance in the NEAR picker -> Press Go below Near -> Confirm

To measure near visual acuity you have first to select the distance in the NEAR picker view, then put the iPad at the selected distance from the eyes and start to measure with the ETDRS. A confirmation message will appear, please ensure that the iPad is at the distance figured at the confirmation message. The last selected distance will appear when you restart the App.

Select RE, LE or BE -> Press Go on the desired distance -> Confirm

The App comes with a different set of letters in order to avoid memorization. Therefore either letters for distance, intermediate and near or right, left and both eyes differ to prevent memorization

Select Settings at the top right -> Select the Notation -> Close

The visual acuity value appears at right and left sides of each row, you can select the notation that will appear on the chart

Select the Contrast Percentage -> Use the Test at the Desired Distance

Low Contrast visual acuity can be measured with the VisionC test, you only have to select the desired percentage