Genetic Eye Disorders in
Cavalier King Charles Spaniels
The cavalier King Charles spaniel has more than its fair share of severe genetic diseases afflicting the eye.* A 2008 study of cavaliers conducted by the Canine Eye Registration Foundation showed that an average of 28% of all CKCSs evaluated had eye problems.
They include hereditary cataracts, corneal dystrophy, distichiasis, dry eye syndrome, entropion, microphthalmia, progressive retinal degeneration, retinal dysplasia, and cherry eye , all of which are discussed on this website. Other hereditary eye disorders, of more minor nature, are not discussed.
Some cavaliers may develop other eye disorders which are considered due in part to the breed's short muzzles and head shapes. Among them are corneal ulcers.
The cornea is the surface of the eyeball, and is a smooth, moist, and usually transparent structure when healthy. It consists of four layers. Corneal ulceration is the loss of one or more layers of the cornea. Corneal ulceration is one of the most common eye diseases in domestic dogs, and is a major cause of blindness due to either scarring or corneal perforation. Corneal ulceration causes pain, redness, light sensitivity, watering eyes, and twitching eyelids. Corneal ulcers vary in severity, and can be classified into grades based on their depth. More superficial lesions tend to be more painful as the nerve endings within the cornea are close to the surface.
Corneal ulcers may be caused by a direct injury, tear abnormalities such as dry eye; external irritants; eyelid or eyelash abnormalities such as distichiasis or entropion; immune-mediated or allergic inflammation; foreign bodies; or the inability to blink.
In a May 2015 report, UK researchers found that cavaliers were among the breeds most commonly affected by corneal ulcers. They calculated a measurement called the craniofacial ratio (CFR), which was the muzzle length (A - B in the photo at right) divided by the cranial length (C - D). They determined that brachycephalic dogs (including the pug, Shih Tzu, bulldog, and cavalier), had a craniofacial ratio of <0.5 and were twenty times more likely to be affected than non-brachycephalic dogs (The cavalier in the photo has a craniofacial ratio of 0.27.)
In our Veterinary Resources section below, we also include citations to veterinary journal articles on other vision disorders for which cavaliers have been treated, including reticulosis and Ehlers-Danlos syndrome.
In many instances, the eye disorders CKCSs experience may be attributed to the brachycephalic shape of their heads. All cavaliers should be examined at least annually by a board certified veterinary ophthalmologist. They are listed on this webpage of the website of the American College of Veterinary Ophthalmologists.
Ocu-GLO Rx is a nutraceutical containing several natural antioxidants in a combination blend formulated specifically for canine eye health. Many veterinary ophthalmologists recommend this product to maintain healthy eyes. Even if your dog has not been diagnosed with a vision disorder, antioxidants contained in Ocu-GLO Rx are considered helpful in keeping dogs' eyes healthy.
Reticulosis of the eyes and the central nervous system in a dog. NL Garmer, P Naeser, AJ Bergman. J.Small Animal Prac.; Jan. 1981;22(1):39-45. Quote: "Bilateral optic neuritis was diagnosed in a 5-year old dog, which had been blind for two days. ... CASE REPORT A 5-year old, 10 kg, male Cavalier King Charles Spaniel was examined because the dog had appeared blind for two days. ... Vision returned after corticosteroid therapy. Two weeks after the end of this treatment the dog became blind again and, in addition, showed ataxia. Post-mortem examination revealed changes in both the central nervous system and the eyes. The histopathological changes observed were consistent with those of reticulosis.
Ehlers-Danlos syndrome in a dog: ocular, cutaneous and articular abnormalities. KC Barnett, BD Cottrell. J.Small Animal Prac. - Journal of Small Animal Practice; Oct. 1987;28(10):941-946. Quote: "Ehlers-Danlos syndrome (EDS) is an hereditary connective tissue disease in man in which the skin is easily torn. A similar condition has been described in dogs and other animals. This case report records a case in the United Kingdom in which the whole syndrome was exhibited: skin fragility, joint laxity and ocular signs of bilateral lens luxation, cataract and corneal oedema. It is the first report of ocular signs in EDS in the dog and joint laxity has been reported only rarely. ... A crossbred bitch (Cavalier King Charles Spaniel x Rorder Collie bitch) was presented at the age of 12 months for investigation of failing vision. ... The case reported here was a Cavalier King Charles Spaniel x Border Collie; neither breed has previously been implicated."
Angiostrongylus vasorum in the anterior chamber of a dog's eye. M. C. A. King, R. M. R. Grose, G. Startup. J.Small Animal Prac.;June 1994;35(6):326-328. Quote: "An unusual case of Angiostrongylus vasorum infestation occurred in a three-year-old female cavalier King Charles spaniel. The dog presented with signs consistent with right otitis interna, followed by the appearance of a free-swimming nematode in the anterior chamber of the right eye. The dog died of acute heart failure before surgical removal of the parasite was possible. Post mortem examination confirmed the presence of large numbers of worms in the pulmonary artery and right ventricle. These worms were identified histologically as A vasorum."
Control of Canine Genetic Diseases. Padgett, G.A., Howell Book House 1998, pp. 198-199, 239.
Ocular Disorders Presumed to be Inherited in Purebred Dogs. Genetics Committee, A.C.V.O. 1999.
Guide to Congenital and Heritable Disorders in Dogs. Dodds WJ, Hall S, Inks K, A.V.A.R., Jan 2004, Section II(88).
Breed Predispositions to Disease in Dogs & Cats. Alex Gough, Alison Thomas. 2004; Blackwell Publ. 44-45.
Ophthalmic Disease in Veterinary Medicine. Charles L. Martin. Manson Publ. 2009; page 475, table 15.1. Quote: "Presumed Inherited Ocular Diseases: Table 15.1: Breed predisposition to eye disease in dogs: Cavalier King Charles Spaniel: ... ."
Breed Predispositions to Disease in Dogs & Cats (2d Ed.). Alex Gough, Alison Thomas. 2010; Blackwell Publ. 53.
Ocular conditions affecting the brachycephalic breeds. Peter G.C. Bedford. 2010. RVC. Quote: "There are two types of disease which affect the eye of the brachycephalic breeds and both are directly or indirectly related to genetic predisposition. First and by far the commonest are those conditions which are due to be conformation of skull and are related to the exophthalmos which is the common feature of these breeds. Second there are those conditions which have been unwittingly bred into some brachycephalic breeds in the pursuit of desired breed characteristics. In this lecture I will present an overview of all the diseases that the small animal practitioner is likely to encounter in the brachycephalic breeds of pedigree dog. The fourteen breeds I have included for discussion are the Affenpinscher, Boston Terrier, Boxer, Bulldog, Cavalier King Charles and the King Charles Spaniels, (mesaticephalic) French Bulldog, Griffon Bruxellois, Japanese Chin, Lhasa Apso, Pekingese, Pug, Shih Tzu and Tibetan Spaniel. ... Corneal Lipid Dystrophy: The term applies to the characteristic cholesterol and triglyceride deposits in the superficial corneal stroma seen most commonly in the Cavalier King Charles Spaniel. It is clinically benign and seldom affects vision to any noticeable degree. ... Hereditary Cataract: Hereditary cataract is seen in the Boston Terrier and the Cavalier King Charles Spaniel. ... Microphthalmos (MoD): Again the American literature suggests that microphthalmos (MoD) may be inherited in the Cavalier King Charles Spaniel."
Ocular Disorders Presumed to be inherited in purebred dogs. Genetics Committee of the American College of Veterinary Ophthalmologists. Blue Book 6th Ed. 2013. pp. 241-247.
Blindness: A Step-by-Step Approach to Diagnosis. Alison Clode. NAVC Clinician's Brief. April 2014;14-15.
The genetics of eye disorders in the dog. Cathryn S. Mellersh. Canine Genetics & Epidemiology. April 2014. Quote: "Inherited forms of eye disease are arguably the best described and best characterized of all inherited diseases in the dog, at both the clinical and molecular level and at the time of writing 29 different mutations have been documented in the scientific literature that are associated with an inherited ocular disorder in the dog. The dog has already played an important role in the identification of genes that are important for ocular development and function as well as emerging therapies for inherited blindness in humans. Similarities in disease phenotype and eye structure and function between dog and man, together with the increasingly sophisticated genetic tools that are available for the dog, mean that the dog is likely to play an ever increasing role in both our understanding of the normal functioning of the eye and in our ability to treat inherited eye disorders. This review summarises the mutations that have been associated with inherited eye disorders in the dog."
Impact of Facial Conformation on Canine Health: Corneal Ulceration. Rowena M. A. Packer, Anke Hendricks, Charlotte C. Burn. PlosOne. May 2015. Quote: "Concern has arisen in recent years that selection for extreme facial morphology in the domestic dog may be leading to an increased frequency of eye disorders. Corneal ulcers are a common and painful eye problem in domestic dogs that can lead to scarring and/or perforation of the cornea, potentially causing blindness. Exaggerated juvenile-like craniofacial conformations and wide eyes have been suspected as risk factors for corneal ulceration. This study aimed to quantify the relationship between corneal ulceration risk and conformational factors including relative eyelid aperture width, brachycephalic (short-muzzled) skull shape, the presence of a nasal fold (wrinkle), and exposed eye-white. A 14 month cross-sectional study of dogs entering a large UK based small animal referral hospital for both corneal ulcers and unrelated disorders was carried out. Dogs were classed as affected if they were diagnosed with a corneal ulcer using fluorescein dye while at the hospital (whether referred for this disorder or not), or if a previous diagnosis of corneal ulcer(s) was documented in the dogs’ histories. Of 700 dogs recruited, measured and clinically examined, 31 were affected by corneal ulcers. Most cases were male (71%), small breed dogs (mean± SE weight: 11.4±1.1 kg), the most common being the Pug (n = 12 affected), the Shih Tzu (n = 4), the Bulldog and the Cavalier King Charles Spaniel (n = 3). ... Morphometric data were collected for each dog using previously defined measuring protocols , measuring 11 conformational features that were demonstrated to be breed-defining: muzzle length, cranial length, head width, eye width, neck length, neck girth, chest girth, chest width, body length, height at the withers and height at the base of tail (all in cm). ... A further morphometric predictor of interest for corneal ulcers was craniofacial ratio, (CFR): the muzzle length (A- B in photo) divided by the cranial length (C - D), which quantifies the degree of brachycephaly, was used to differentiate skull morphologies. ... [B]rachycephalic dogs (craniofacial ratio <0.5) were twenty times more likely to be affected than non-brachycephalic dogs. ... Palpebral fissure width is defined as the straight-line distance (mm) between the medial and lateral canthus. A 1% increase in relative palpebral fissure width was found to increase the risk of ulcers by 1.12. ... This CKCS has a relative palpebral fissure width value of 33.3%. A 10% increase in relative eyelid aperture width more than tripled the ulcer risk. Exposed eye-white was associated with a nearly three times increased risk. The results demonstrate that artificially selecting for these facial characteristics greatly heightens the risk of corneal ulcers, and such selection should thus be discouraged to improve canine welfare."