“Normal” eyelid conformation for dogs is taken to be an almond shaped palpebral fissure (eyelid opening) with the lids resting on the globe and a small amount of scleral show (white area outside the cornea) on the outside corner but none nasally.
The breed standards for many breeds unfortunately call for eyelid conformation that deviates from this ideal. This is important as the eyelid conformation affects eyelid function: to cover and protect the eyes and vitally, to spread the tear film. This means that many breeds are predisposed to eye disease are due to poor eyelid design.
Brachycephalic breeds have reduced orbital space due to the flattening of their facial features. This makes for prominent eyeballs, often poorly covered by the eyelids with excessive scleral show all around. This places these breeds at risk of globe proptosis and also of risk of corneal ulcers and corneral exposure issues due to drying of the central cornea. These breeds often have a prominent nasal skin folds that can have hairs directly touching the cornea causing irritation and also the skin fold pushing the lower lid creating an entropion. At Animal Eye Care we see many dogs with serious corneal disease, up to corneal rupture, resulting from these prominent globes, and medial entropion (the inside eyelid cornea rolling in).