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We all know Brachycephalic breeds like Pugs, Shih-tzus, Boston Terriers and French Bulldogs for example, are considerably more prone to ocular issues. Ocular disease in these breeds develops because of a combination of factors:
Macroblepharon and lagophthalmos (large prominent eyes with little blinking)
- The large eyes that sit far forward do not have adequate protection from the eyelids. A low blink rate allows for excessive corneal exposure and tear film evaporation which in turn leads to chronic keratitis (inflammation of the cornea) and the risk of corneal ulceration.
Macroblepharon and lagophthalmos
Medial canthal entropion (turning in of the eyelids near the nose)
- This leads to hairs chronically rubbing on the conjunctiva and cornea (trichiasis) which again results in chronic keratitis and can lead to ulceration.
Medial canthal entropion
Reduced corneal sensation
- Compared to dogs with longer noses, brachycephalics have reduced corneal sensitivity because they have less branches of nerves innervating the cornea. They therefore do not exhibit the usual pain response associated with corneal disease. This can lead to a delay in picking up on when there is a problem.
- Poor corneal sensation also delays the normal healing response. This is one of the many contributing factors as to why corneal ulceration can go downhill rapidly in these breeds.
- The reduced sensation also results in a reduction in blink rate which leads to subsequent tear film evaporation.
Quantitative and Qualitative tear film abnormalities (poor tear film)
- The tear film is important in protecting the cornea and stopping it from drying out. Brachycephalic tear film is often reduced and of poor quality, it evaporates quicker and with the reduced blinking and exposure increases the risk of ulceration.
Pigmentary keratitis (pigmentation of the cornea)
- Chronic keratitis and tear film abnormalities lead to pigmentary keratitis
- Melanin cells (pigment) are deposited in the corneal layers with chronic inflammation. The pigmentation often starts in the medial corneal and progresses across to affect vision and cause blindness. Sometimes there will be a central band of pigmentation where some brachycephalics are unable to completely shut their eyelids.
Pigmentary keratitis
Is there anything we do to help protect brachycephalic eyes from discomfort and reduce the risk of corneal ulceration?
Yes, thankfully there are some treatments that are available which are based on addressing the underlying problems.
Early detection of any ocular discomfort or change in appearance of the eyes is extremely important in brachycephalics. The earlier an ocular abnormality is detected the quicker treatment can be started. We advise daily ocular lubrication in brachycephalics which is an easy solution to put into place. This will help to protect and lubricate the eyes which is important in dogs that don’t blink enough, it also means that the eyes are being looked at daily.
A lot of patients benefit from medial canthal blepharoplasty surgery. This removes the hairs at the corner of the eyelids nearest the nose that are chronically rubbing the eyes and reduces eyelid length. Once the eyelids are shorter, the dog blink improves and the ocular surface is less exposed.
In cases where tear film abnormalities are present, long term topical medications can be used to stimulate tear film production and improve their quality. These can have the added benefit of reducing the progression of corneal pigmentation.
One of our lovely patients post canthal blepharoplasty surgery
