I took the time to actually measure a scant quarter inch from my left most needle position, and found that the normal foot for my quilting machine gives me a scant quarter inch seam, but I still had problems keeping the fabric lined up properly due to my visual problems. DH was watching me struggle, and suggested using a strip of day-glo orange duct tape across the bed so I can line the fabric up and keep my seams straight. I got the idea of using a permanent ink pen to make a line on the machine itself, so that when I move the tape to change bobbins, or need fresh tape, I can just stick it back down following the line. I do turn under the end of the tape facing me so I can pull it loose as needed.
Before you all panic at the idea of actually writing on my machine with permanent ink, I did it knowing that I would always need this help to make my seams correctly. When I am working with other seam sizes, I just pull the tape, ignore the line, and use a piece of tape put down at the 5/8" line. My lines are color coded. This has certainly helped increase my accuracy when piecing, since my 1/4 inch foot is too far away for me to see clearly.