Awww sweetie!!!
I totally feel your pain. I just lost my Cocker Spaniel in January that I had for over 11 years and to be 100% honest, words cannot even describe how I felt. There is literally no way that I can type what I felt into text. It just isn't possible. However, let me tell you this. PLEASE don't spend all your time (and trust me, I know it is hard as hell) worrying about "something happening"...you really do need to enjoy every minute you have with them. My Cocker also had an enlarged heart, as well as Lung Cancer, Arthritis, she was deaf, completely blind in one eye, and about 90% blind in the other. However, even with all those terrible problems, she was still the best dog in the world, and she acted just like herself, like she always did, until her very last day. July 19th hit the 6 month mark since her passing exactly. I still sleep with her toy monkey every single night. I'll never stop. I feel like she is with me when I hold it close, next to my heart. I won't go into detail about what happened when she passed, as it is an extremely long story, and one that is still WAY too painful for me to talk about. It is still so fresh in my mind...and when I start talking about it, I break down. I am already crying now.
However, my whole point of this post was to tell you to please...PLEASE, just enjoy every minute you have with your precious baby. I HOPE and PRAY that the Lord allows him to stay with you for many more years to come, but let me tell you, you will SO regret spending all your days worry about "what if" when God does in fact decide to take him. It will eat you up inside. I spent the last several months with my Cocker, doing nothing but worrying, crying, being sad, upset, and just over all miserable because I knew her heath was seriously declining...when ALL I should have been doing was loving her, hugging her, kissing her, laying with her, sleeping with her, and spending AS MUCH time with her as possible. You WANT these moments...you NEED these moments...because once they are gone, you won't get them back.
You have to look at it this way, him being blind isn't a wonderful thing, and it isn't something that any one of us would wish on our loving pets...but it ISN'T the worst thing either. HUMAN BEINGS live every single day never to see a thing, and they do just fine. He will be fine as well. There are things much worse that could happen. He can live and be totally happy and healthy even without having his vision. Honestly, this is how you have to look at it...
So what is my best advice to you right now? Simply this. LOVE HIM.