Sources of error:
Do not be disappointed, if there is no visible success right at the beginning. Here are a few possible sources of error cited:
Perhaps you have chosen too little contrast objects. Try to exercise at various objects, until you have a sense of what objects are well suited for the exercise and what less.
The selected objects may be too far away, or it is already too dark outside. And most important, do not blink after opening your eyes.
Do not use closely patterns for the exercise (stripes, fonts ...). In these cases, the brain will attempt to focus and will be irritated by the parallel pattern. The brain moves the eye muscles until a sample shows a sense, and tends to interpret the lines as a single one, and the letters can not be deciphered. You would do easier by looking at the writings at a right angle than farther sideways.
So, you can control the improvement of your eyesight at the beginning by reading great writings in the distance, but for the exercises these patterns are poorly suited.
Monitors and TV screens are not suitable at the beginning of the exercises. But after a few months you will be able to watch tv without glasses.
Actually you should not exercise looking through windows, sunglasses etc. , as these can be dirty, they also often may reflect, or reduce the contrasts, and generally distort the picture.
It is much too dark inside buildings illuminated by electric light for the exercises. Outside, during bright days, you have optimal training conditions.
The most common sources of errors are in any case: to little light, the wrong objects and blinking after opening the eyes.