Sighting and less than 20:20 vision

My first open water race is coming up next month. I've practiced sighting simulations in the pool, but the practice buoy is only at the other side of the pool. I assume the real thing will be much more distant. I do not have access to open water to practice before my race and am worried about whether I will be able to see the buoy. Just how far away is customary? The swim in question is the Oxford-Bellevue Sharkfest, a 1500 m across the Tred-Avon River in Maryland. It is a straight line, not a triangle. Since this is my first such event, my goal is just to finish safely within the 40 minute DQ cut-off. For Masters practice I have been wearing Speedo Vanquisher -2.00 strength optical goggles in order to read the whiteboard. (I can read the digital clock fine without magnification). I find these goggles uncomfortable after about 500 yards. When not at formal practice, I usually wear Aqua Sphere Lady Kaiman. They fit me great and are much more comfortable, but aren't available as optical goggles. I haven't found any optical goggles that fit like the Aquasphere or are open water style. So my question is do I wear the comfortable goggles that compromise my vision or the uncomfortable ones that let me see better?