You can download an Acrobat file of eye-charts with different colour contrast. Normally you don't see eye-charts with different colours. In Vision Training they are used because the refractive index varies with the frequency of light. For example, blue has a greater refractive index than red.

Choose the colour you find most comfortable to look at and start using that and gradually go on to be comfortable with the traditional black and white chart.

Making your own Eye-chart

You may be bored looking at the same letters all the time. Why not make your own Eye-chart. This table show you the proper distance from which to view the chart, the letter height in mm., letter height in point, and font size in points. Choose ARIAL or CURRIER bold since these fonts resemble the Snellen letters.

This table shows the dimensions of the 20/20 line at different distances.

This table shows the specific font sizes for each line on the eye-chart

Place your eye chart where there is good light during the day. Measure out the proper distance. Place a marker on the floor indicating the correct distance in which to view the chart. Then check each eye and notice which line you can see on the chart. Note the 20/?? indicating your visual acuity in that eye. Many people have a difference between the eyes. Your first objective will be to make both eyes the same and then go on from there to be able to see the bottom line of the chart.

Visual acuity is defined as the focusing power of the eye, or the ability to separate objects. Astronomers discovered that if the distance between two stars is less than 1 minute of an arch then most people would see them as one rather than two. The normal resolving power of the eye is therefore defined as the ability to detect a gap of width 1 minute of arch.

The height of a letter for any given decimal acuity value can therefore be determined by a simple relationship.

Height of letter = 8.726 mm / height of letter

If the decimal acuity is multiplied by 100 the result is percentage acuity.