Perhaps something to keep an eye on Maria
Bathing with cooled boiled water/black tea is good & soothing. The majority of dogs have some eye discharge to some extent or another - but some more than other. You know Dennis best & will notice if there any changes to his eyes or their discharge.
Possibly after all the trauma he has been through & medication he has been on, he maybe getting a touch of dry eye but if you have any concerns you could just check with your vets
You can by visco tears at the chemists (artificial tears licenced for humans ) if you think it might help - if his 3rd eye lid starts to close over his eye or they are starting to look red aswell as gunky, then best to get them checked out