The sinus infection is such a serious disease that can cause the brain to be damaged. To speak it in detail, it is a special type of cerebrovascular disease which has the great connection with the blood circulation around the eyes. Once the eye pressure is unstable, it can cause the eyes get double vision. That is why the sinus infection has the relation with the double vision. You'd better go to see the doctor and accept the treatment.
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.
Actually, you should know that sinus infection is a disease in your nose. And it is said that sinus infection could lead to headache and some other symptoms. Because every part of our head is interconnected, one part is able to affect other parts, let alone your eyes. So, according to your description, it is highly probable that your double vision is resulted from sinus infection. But you shouldn't be over frightened since sinus infection is not deadly. However it is chronic so you have to take it seriously and take immediate actions to treat it, the best place is a large and professional hospital.