There are several symptoms of sinus infection which are the most common ones such as runny nose, congestion and headache. The patient maybe will get a fever and feel a little weak and his eyes may be very sensitive to the light. And it may causes double vision in some sever cases of sinus infection.
Since a bad infection in the sinus which goes untreated will probably impair the muscles in the bottom of the eye, which will move the eye up and down, a blurred or double vision will occur.
If your double vision was related to your sinus infection actually, it will improve as the sinus infection improves.
However, it is possible that your double vision is caused by other factors, you are suggested to visit your eye doctor if the symptoms continues for a long time.