Hello, my name is***** and I have over 20 years of experience as a veterinarian. I'm sorry to hear that your fellow Mochi has swollen eyes that are painful and have a purulent discharge.
My concern is that he has an underlying problem that is predisposing him to get an infection because he has a previous history of eye infections that respond to medication but return.
One possible underlying problem is KCS or dry eye. This is an autoimmune like condition in which the body attacks the tear glands and scarring results with decreased tear production. This can be very uncomfortable for them. With poor tear production the eyes don't get dirt and bacteria flushed out as it should be, his eyes will be itchier and he will rub them more, thus predisposing toward infections.
KCS is diagnosed by measuring tear production with a special test called a Schirmer tear test, which measures the amount of liquid tears in the eyes at the time they are tested. Sometimes if a dog is stressed or excited we get normal levels, when most to the time they are not. So with a normal test level if I have a strong suspicion that tear production is poor I will ask to retest them at a later date.
Ideally with KCS we would use an immunosuppressive eye drop to knock down his immune system's reaction and allow his tear glands to start functioning again. Common immunosuppressive medications include Tacrolimus or Cyclosporine eye drops. These drops or the oil vehicle that they are in can be very irritating, especially when his eyes are already so sensitive. We often need to start with medication at a lower percentage concentration level to acclimate the eyes and then increase the percentage in the product.
Unfortunately the other problem is that these drops can take several weeks to start working. If you stop too soon then he won't respond. In the meantime I often will recommend using artificial tears too to keep their eyes more comfortable. You can use any artificial tear product while waiting for the immunosuppressive drug to work, but the drops rather then the gel formulations seem to be a little more soothing.
You can compress his eyes with a warm cloth, flush them with sterile saline to remove debris, then use artificial tears to soothe his eyes until he can see his veterinarian, except for an 8-12 hour period before his appointment when they need to measure his levels of tear production
Another possible cause of repeated infections are allergies, which make his face very itchy, and when he rubs her face he accidentally introduces bacteria into his eyes.
These dogs benefit from warm compressing, flushing the eyes and artificial tears too.
Ideally you would start with a veterinary visit to measure tear production.
In the meantime it is fine to use artificial tears every few hours as needed.
Best of luck with your fellow, please let me know if you have any further questions.