Macropalpebral Fissure
Description of the Disease and Clinical Picture
 
The upper and lower eyelids form an opening (fissure). In each species and breed of animal, the eyelids have a length that allows their function of supporting and protecting the eyeball to be unhindered. If the length of the eyelids is too large, then the upper and lower eyelids will form an oversized opening (macropalpebral fissure), in which case the eyeball will protrude excessively from the eye socket. Dogs with macropalpebral fissure often have issues with incomplete eyelid closure (lagophthalmos), and some even sleep with their eyes open. Because the eyeball is excessively exposed to external environmental factors, such dogs will have problems with chronic irritation and scarring of the eye surface, pigmentary keratitis (development of pigmented scar tissue on the corneal surface), keratoconjunctivitis, ulcerative keratitis, and dry eye, and may also be prone to eye proptosis (dislocation of the eyeball over the edge of the eyelids). These are all factors that can jeopardize vision. Breeds in which this anomaly commonly occurs are brachycephalic breeds: Pekingese, Pug, Shih Tzu, Lhasa Apso, and Boston Terrier.
 
Therapy
For most patients, medical therapy is sufficient. The eye must regularly be protected with lubricants, the tear film must be stabilized, and any complications, such as keratitis or ulcers, must be adequately managed. In severe cases, surgical correction is undertaken—reducing the eyelid fissure, achieved by medial canthoplasty. In dogs that are prone to eyeball proptosis, surgical reduction of the eyelid opening is mandatory.