There are several types of eye problems, some more serious than others. For a case of mild discharge where your pet's eyes are clear and open, try bathing the eyes in saline solution. If the eyes are open but look red, bathe the eyes but get them checked soon by a vet.
Eyes which are
A prolapsed eye is an emergency situation and should be gently but firmly bandaged with a saline soaked sterile pad and non-adhesive bandage.
Brachycephalic breeds (those with short, broad heads such as pugs, pekes, boxers and bulldogs) should never be held by the scruff of the neck as there is a risk of causing an eye prolapse.
When in doubt about any medical condition, please see your vet.