Sorry to hear this. I have a 12 yr. old yellow lab starting to show some similar symptoms. This past fall she was panting excessively and going in circles among other things. I took her in for annual checkup and the Vet thought it might be a heart/cardio issue. Told me to watch her diet and if she started eating less to bring her back for tests. Those symptoms went away when it cooled off, but she still has odd behavior at times. Her up close and peripheral vision is about gone, but she can see a squirrel at 200'.
Some days she seems perfectly normal, like the good 'ole days. Hopefully your best friend still has some good days ahead.
