There's a special kind of panic that comes when your rooster, the one who's been strutting around for twelve years, starts tripping over his own feet. And when his hen-mate is leaking grey mucus like a tiny, feathery faucet, that panic has a very good reason to show up. The original poster isn't asking whether this is serious. They already know it is. They're asking *which* kind of serious, because there's a world of difference between "needs antibiotics" and "needs a miracle."
Let's be honest: the combination of thick nasal discharge and sudden vision problems is the kind of fowl play that makes even seasoned keepers feel a little wobbly. Respiratory infections in chickens are common enough that most of us can rattle off a few names, coryza, mycoplasma, infectious bronchitis. But partial blindness? That's not a typical party trick for a cold. The fact that the rooster can see things far away but can't focus on his food dish suggests something neurological or pressure-related, not just a stuffy nose. Swollen sinuses can press on the optic nerve, sure, but so can a few other unpleasant possibilities.
You need a vet. Not just any vet, one who treats birds, preferably in person. I know that sounds like the least helpful advice in the world when you're desperate and the nearest avian vet is two counties over. But this is where "I love him very much" meets the hard truth of chicken keeping. A twelve-year-old rooster is a senior citizen by any standard, and his immune system has probably been running on loyalty and habit. Guessing which antibiotic to use, and getting it wrong, could waste time he doesn't have. A vet can swab the discharge, run a culture, and tell you whether you're dealing with bacteria, a virus, or something else entirely. They can also check whether that blindness is reversible.
In practical terms, what would we tell a reader who asked? Isolate the sick birds immediately, even if the hen seems less affected. They've already shared it with each other, but the rest of your flock doesn't need an invitation. Offer the rooster wet mash in a shallow, brightly colored dish right under his beak, he can't see it, but he can smell it, and the texture might trigger his feeding reflex. Hand-feed him if you have to. Every day without food or water chips away at his chances. And while the poster asked us not to suggest culling, we won't. That's not our call. But we will say this: love doesn't mean letting him starve slowly because you hoped he'd eat on his own. If he stops eating altogether, the kindest intervention might not be a needle, it might be a syringe full of electrolyte solution and a long, patient afternoon.