Check that you're not crossing your eyes rather than using a divergent gaze. Also try changing the distance between your eyes and the book see when the blip is the most comfortable for you. Will it affect the quality of your photoreading if it's really wide? Nope, your worrying does though.
The unevenness of the width of the blip is merely the angle of the book to your eyes and usually just indicates that one eye is stronger than the other.It is ok you're still getting it as long as you can notice the four corners of the book.
Alex
