Cataracts are the most common cause of treatable blindness in dogs. They are often classified into 4 categories on the basis of the degree of lens opacification. Immature cataracts involve only a small portion of the lens and still allow tapetal reflection, although vision may be impaired. Incipient cataracts involve between 10% and 15% of the lens. Mature cataracts affect the entire lens and affected dogs are severely visually impaired. Hypermature cataracts have undergone liquefaction and resorption, and the degree of visual impairment depends on the amount of liquefaction. Genetic abnormalities are the primary cause of cataracts, followed by diabetes mellitus.

This study examined 244 dogs presented to the University of Tennessee from January 2001 to December 2002. The average age was 8 years (range, 6 months to 16 years). There were 54 breeds represented, but 11 breeds had 5 or more dogs presented. Forty-two of the dogs had diabetes mellitus. A previous study has shown that 75% of diabetic dogs develop cataracts within a year of diagnosis. Some dogs had lens-induced uveitis from the release of antigenic lens proteins from the lens capsule. Lens-induced uveitis can make surgery difficult or impossible. In this study, 5 dogs with mature cataracts and 49 of the dogs with hypermature cataracts had lens-induced uveitis. The most common treatment for cataracts is surgical removal with phacoemulsification. At this referral institute, the preferred stage for phacoemulsification is the immature cataract. In this study, 244 dogs were evaluated and 159 were not able to have surgery. The most common reason for not having surgery was retinal degeneration.

COMMENTARY: Cataracts have been reported to be the most common eye disease of purebred dogs and the leading cause of blindness in adult dogs. With the evolution of new techniques available to veterinary ophthalmologists, referral should become commonplace. The Canine Eye Registry Foundation (www.vmdb.org) has information about breed heritability and maintains a registry of purebred dogs that ACVO diplomates have examined and have found to be unaffected by major heritable eye disease.

Outcomes of dogs presented for cataract evaluation: A retrospective study. Adkins EA, Hendrix DVH. JAAHA 41:235-240, 2005.