In Labrador Retrievers, several different types of cataract may develop, most of which are assumed to be phenotypic variations of the same genetic disorder.1,2 In this breed of dog, 50% of PPCs are detectable by 2 years of age.1 In a study3 of 1,399 Labrador Retrievers, 5.5% were affected by cortical cataracts (most commonly PPCs).
Dogs that belong to members of the Dutch Labrador Club must undergo an ophthalmic examination performed by an ECVO-accredited examiner prior to breeding. According to the Dutch Labrador Club regulations, both dogs of a breeding pair must have a current ophthalmic report (ie, examination must have been performed within the year prior to birth of the litter).4 If a dog is affected by cataracts or another ophthalmic disease that is presumed to be inherited, it is excluded from the Club's breeding program.
It has not yet been proven that PPC development is genetically related to the other types of cataract in Labrador Retrievers, but it has been suggested that it is likely.3,5 Also, it has not been elucidated whether PPC is a progressive condition. Some breeders regard PPCs as a stationary disorder without visual impairment and accept inclusion of affected dogs in the breeding population. However, extensive progression of posterior polar subcapsular cataracts in 8 of 40 (20%) Labrador and Golden Retrievers has been reported.3 In Entlebucher Mountain dogs, the frequency with which this type of cataract develops into cataracts that cause visual impairment is 8%.6 For the Labrador Retriever population in The Netherlands, no information on the progression of PPCs is available because affected animals only rarely undergo ophthalmic reexamination.
Hereditary retinal degeneration or PRA in dogs is known to be often complicated by cataract development. This is most likely associated with changes in the vitreous humor, secondary to degeneration of the retina, which lead to a change in the nutritional supply of the lens. The metabolism of the lens is subsequently altered, thereby resulting in the development of cataracts. The initial changes typically occur in the posterior cortex.7 The incidence of secondary cataract in dogs with PRA is yet unknown.
The purpose of the study reported here was to assess the prevalence and distribution of types of cataract, investigate the effects of selective breeding on cataract development, and identify the relationship between PPCs and other types of cortical cataracts in Labrador Retrievers in The Netherlands.
European College of Veterinary Ophthalmologists
Posterior polar (triangular) cataract
Progressive retinal atrophy
GCS-Datamanager, version 2007, Genetic Counselling Services, Hillegom, The Netherlands.
Curtis R, Barnett KC. A survey of cataracts in Golden and Labrador Retrievers. J Small Anim Pract 1989;30:277–286.
Name of Web site or document. Available at: www.nederlandselabradorvereniging.nl/fileadmin/user_upload/roswitha/ABC_ARTIKELEN/FOKBELEID_12_april_2008_PDF.pdf. Accessed September 12, 2008.
Gelatt KN, Davidson MG, Nelms SR, et al. Diseases of the canine lens and cataract formation. In: Veterinary ophthalmology. 4th ed. Ames, Iowa: Blackwell Publishing Professional, 2007;874.
Armitage P, Berry G, Matthews JNS. Statistical methods in medical research. 4th ed. Boston: Blackwell Science Ltd, 2002;504–509.