Hi, 

These are called eye gnats and they can be quite a nuisance. They are attracted to the mucus we secrete in our eyes or our sweat as a source or water and salt. They breed in wet organic matter so leaf litter debris from the woods is a prime area for them. 

There isn't a treatment you can do to your yard to deter them since they can just fly in from other areas. Look for sources of standing water to eliminate since this will also be helpful to control mosquitoes. 

Sometimes insect repellents can work for eye gnats, but I agree with you, personally, I have not found any to be effective either. You could try different types to see if others work.  Head nets over hats are the best to keep them away and eventually their season will pass. If they are a nuisance on a porch, using fans or screening areas are best. They aren't strong fliers so a light breeze will help keep them away. Traps are also not ideal since they will likely only be effective temporarily and they could also trap beneficial insects and predators we rely on to help with their control. 

Good luck! 

Emily