Figure 2: This side - on (lateral) view of a dog's eye shows obvious protrusion of the eyeball or exophthalmos due to inflammation of the extraocular muscles (extraocular myositis).
In this case, we're talking about muscles that move the eyeballs - extraocular muscle myositis - and muscles that your dog uses to chew - polymyositis, dermatomyositis and necrotising myopathy.