by John V. Ioia, MD, PhD

Ophthalmology: Reprinted from the AKC Gazette Magazine, September 2020

I thought that a brief review of eye conditions in the Cavalier might be interesting to breeders, exhibitors and pet owners.  This was prompted by a remark suggesting that cataracts and particularly inherited cataracts were rampant in our breed.  A review of literature and discussions with several long-term breeders suggest that nothing could be further from the truth, but I am getting ahead of myself.

Eye conditions or diseases in the CKCS include cataracts, corneal dystrophy, distichiasis entropion, microphthalmia, progressive retinal atrophy, retinal dysplasia, keratoconjunctivitis sicca, also known as “dry eye” and Corneal Lipid deposits or Corneal Dystrophy.

An internet statement using a 1999 study ([1]) suggests that an average of 30% of CKCS have “Eye problems.”  This statement is derived from 2009 source reviewing Corneal Dystrophy in the CKCS and may lead to a gross misunderstanding of eye issues.  Let’s look at the some of the problems that can occur in our breed.

Progressive retinal atrophy (PRA) is a group of genetic diseases seen in some breeds of dogs, is similar to retinitis pigmentosa in humans and is possibly the most serious of the eye diseases.   PRA Is characterized by degeneration of the retina, causing progressive vision loss and culminating in blindness. The condition is stated to occur in many breeds, is inherited as an autosomal recessive trait, with the exception of the Siberian Husky (an X chromosome linked trait) and the Bullmastiff (an autosomal dominant trait).  There is no treatment for PRA and the elimination of the disease in these breeds is based on testing and removing affected specimens from breeding.  While CKCS are mentioned in discussions of PRA, there are no statistics and I could find no history of affected dogs among the breeders that I contacted.

Keratoconjunctivitis sicca, or “dry eye” is a very serious autoimmune and inherited disease. It manifests itself by a loss of tear production from the dog’s lacrimal glands and requires constant treatment with eye drops and can progress to blindness.  It is associated genetically with a disease called “Curly Coat.”  Fortunately, it is both fairly rare and can be easily genetically tested so that carriers can be eliminated from breeding populations. ([2])

The next two for discussion are Distichiasis and Entropion, which effects the eyelid.  A distichia is an eyelash that arises from an abnormal spot on the eyelid. This abnormality, attributed to a genetic mutation, is known to affect dogs and humans. Distichia (the abnormal eyelash) usually exits from the duct of the meibomian gland at the eyelid margin. These lashes are usually multiple and sometimes more than one will arise from a duct.  They can affect either the upper or lower eyelid and are usually bilateral.  The lower eyelids of dogs usually have no eyelashes.  Distichia may cause no symptoms if the lashes are soft, but they can irritate the eye and cause tearing, squinting, inflammation, corneal ulcers and scarring. Treatment options include manual removal, electrolysis, electrocautery, CO2 laser ablation, cryotherapy, and surgical removal.

Entropion is often lumped in with or confused with Distichia since it involves the eyelid.  Entropion is a medical condition in which the eyelid (often the lower lid) folds inward. It is very uncomfortable, as the eyelashes continuously rub against the cornea causing irritation. Entropion is usually caused by genetic factors.  This is different from when an extra fold of skin on the lower eyelid causes lashes to turn in towards the eye (epiblepharon).  In epiblepharon, the eyelid margin itself is in the correct position, but the extra fold of skin causes the lashes to be misdirected.  Entropion can also create secondary eye pain, self-trauma, scarring of the eyelid, or nerve damage. The upper or lower eyelid can be involved, and one or both eyes may be affected.  When entropion occurs in both eyes, this is known as “bilateral entropion.”  Cases of trachoma infection may cause scarring of the inner eyelid, which may cause entropion.  Treatment is a relatively simple surgery in which excess skin of the outer lids is removed.  The prognosis is excellent if surgery is performed before the cornea is damaged. ([3])

Microphthalmia (microphthalmos) is an inherited defect in which, as the name suggests, one or both of the dog’s eyes is smaller than normal, resulting in restricted vision and possible blindness.  While it is stated as being “Particularly common in the Cavalier King Charles spaniel, according to the American College of Veterinary Ophthalmologists (ACVO)” ([4]), my review of the article “Ocular Conditions Affecting the Brachycephalic Breeds” provides only a statement that “The American literature suggests that microphthalmos (MoD) may be inherited in the Cavalier King Charles Spaniel (3)” with no statistics or factual data.  I could not find literature with data providing the incidence or prevalence of Microphthalmia in the CKCS.

My last subject is the cataract.  Inside the eye is a lens that focuses light on the back of the eye or the retina. Vision occurs at the retina. The structure of the eye is similar to a camera, which has a lens to focus light on the film. A cloudy or opaque lens is called a cataract.  A common cause of juvenile cataracts in the dog is inherited disease but other causes include injuries, diseases such as diabetes mellitus and spontaneously or age related ([5]).  Hereditary cataracts can affect many breeds of dogs including the American Cocker Spaniel, Labrador Retriever, French Poodle, Boston Terrier and the Welsh Springer Spaniel to name a few.

The effect of a cataract depends on how much it occludes vision.  A cataract which occupies 15% of the lens is considered incipient, requires magnification to be seen and causes no visual defect.  At 30% of the lens or if only one eye is affected there will be little visual loss. At 60% impairment occurs and at 100% the dog is blind.

A study that is often referred to as demonstrating hereditary cataracts in the CKCS was performed at a French Clinic ([6]).  A total of 2739 dogs presented to the Ophthalmology Unit from 2009 to 2012.  Four hundred and four dogs (14.7%) (716 eyes) were diagnosed with a cataract. Only 6 were Cavalier King Charles spaniels.  Fifty-four breeds were represented.  The etiology was determined for each dog, along with their medical history, age of onset, stage of progression, location of opacities, and ocular lesions associated were evaluated for each etiology.  The causes of cataracts included aging (22.8%), PRA (12.4%), congenital (5%), diabetes mellitus (4.7%), trauma (3.7%), uveitis (3%), and hypocalcemia (0.2%). In 20.3% of the cases, the etiology could not be determined.   A congenital cataract diagnosed in one West Highland White Terrier, one Akita, two Australian Shepherd dogs, and two Cavalier King Charles Spaniels.  Only the Yorkshire Terrier was considered to have a breed predisposition.  A lesson to be learned; while cataracts do occur in the CKCS, they are certainly not rampant in the breed and the sampling in this study was much too small to assign an inheritance percentage.


  1. Corneal Dystrophy and the Cavalier King Charles Spaniel. Retrieved 14 November2009.
  3. Ocular Conditions Affecting the Brachycephalic breeds, Peter G C Bedford, Chair of Veterinary Ophthalmology, Royal Veterinary College, University of London, Hawkshead Lane, North Mymms, Hatfield, Herts AL9 7TA
  6. Epidemiology and clinical presentation of canine cataracts in France: a retrospective study of 404 cases. Elise Donzel, Léa Arti, Sabine Chahory. Vet. Ophthal. March 2017;20(2):131-139