I am so sorry for your loss of Smokey. I know what you are going through, and how difficult it is for you, I had to make the decision to end an older cat's suffering also. A year ago in January, my cat Midnight, was diagnosed with glaucoma in both eyes and was already blind because of it. At first the vet thought that Midnight's sight could be partically restored, but glaucoma is a more serious problem in animals than it is in people. In spite of all our efforts, the glaucoma kept progressing and causing more damage, and the blindness became permenant. The pain during the flare-ups of inflamation that Midnight had was getting more difficult to manage. The general decline Midnight was in was also becoming more rapid, and the option of surgically removing both eyes was not recommended by the vet.
Last August, when Midnight had just turned 14, she had another flare-up of severe pain and inflamation in both eyes. I increased the medication according the vet's instructions, but it didn't seem to be helping. I made the necessary decision and asked the vet to make a house call.
At first I felt guilty about ending Midnight's life, but now that some time has passed, I am 100% sure that I did the right thing and the best thing for Midnight.
My thoughts are with you at this difficult time.