I have a long history of sinus infections and inflammation. In the past, I noticed the onset of mild eyestrain coincidentally with sinus attacks. However, my eyes' condition has never been as bad as these days with no improvement - actually more of a constant decay - since last February, and I have not had once a sinus issue or a cold since early 2020, clearly because of the wearing of a mask and all the other COVID-related hygiene habits. I should add that my eye symptoms have become worse in spite of doing visual therapy for the past year and a half, and visiting specialists such as orthoptists and neuro-ophthalmologists, that I had never consulted before.
So, no, I am not sure there is an evident link between my sinuses and my eye strain. Perhaps an illness such as a cold may aggravate my eyes' condition, but my eyestrain is definitely caused by other triggers than sinus inflammation.