Representatives of the British breed of cats are brachycephalic, meaning they have a spherical head due to a shortened muzzle. This unique skull shape differs from that of non-brachycephalic breeds.

The spherical head is a breed standard that adds to their charm, but it also contributes to the atypical anatomical structure of the nasolacrimal canals. In brachycephalic cats and dogs, these canals often have some curvature and deformation. In severe cases, this can impede the flow of tears into the nasopharynx.
Many owners notice brown crusts in the corners of their cat's eyes after sleep, which is a normal occurrence. While tears are clear when secreted, they can linger on the fur and oxidize in the air, resulting in a brown discoloration. The brown crusts (which may sometimes have a reddish tint) are simply dried, oxidized tears.