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Characteristics of, prevalence of, and risk factors for corneal pigmentation (pigmentary keratopathy) in Pugs

Amber L. LabelleDepartment of Veterinary Clinical Medicine, College of Veterinary Medicine, University of Illinois, Urbana, IL 61082.

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Christine B. DresserDepartment of Cuyahoga Valley Veterinary Clinic, 3850 Brecksville Rd, Richfield, OH 44286.

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Ralph E. HamorDepartment of Veterinary Clinical Medicine, College of Veterinary Medicine, University of Illinois, Urbana, IL 61082.

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Matthew C. AllenderDepartment of Comparative Biosciences, College of Veterinary Medicine, University of Illinois, Urbana, IL 61082.

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Julia L. DisneyDepartment of Veterinary Clinical Medicine, College of Veterinary Medicine, University of Illinois, Urbana, IL 61082.

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Abstract

Objective—To determine the characteristics of, prevalence of, and risk factors for corneal pigmentation (CP) in Pugs.

Design—Prospective cross-sectional study.

Animals—295 Pugs > 16 weeks old.

Procedures—Ophthalmic examination of the anterior segment of each eye was performed, including determination of tear film characteristics (Schirmer tear test and tear film breakup time) and corneal sensitivity. Digital photographs of the head and each eye were obtained. Corneal pigmentation of eyes was graded as absent, very mild, mild, moderate, or severe. Signalment and medical history information and American Kennel Club registration status were recorded.

Results—CP was detected in at least 1 eye of 243 of the 295 (82.4%) Pugs; CP was typically very mild or mild. Detection of CP was not significantly associated with coat color, age, eyelid conformation, or tear film characteristics but was significantly associated with sex of dogs. The severity of CP was not significantly associated with American Kennel Club registration status or age, but was significantly associated with sex, tear film characteristics, and coat color. Iris hypoplasia was detected in 72.1% of the Pugs. Iris-to-iris persistent pupillary membranes were detected in 85.3% of the Pugs.

Conclusions and Clinical Relevance—Prevalence of CP in Pugs in this study was high. Unexpectedly high prevalences of iris hypoplasia and persistent pupillary membranes were also identified. The condition identified in these Pugs was a pigmentary keratopathy, rather than pigmentary keratitis or corneal melanosis. This condition may have a genetic basis, and further studies are warranted to determine etiology.

Abstract

Objective—To determine the characteristics of, prevalence of, and risk factors for corneal pigmentation (CP) in Pugs.

Design—Prospective cross-sectional study.

Animals—295 Pugs > 16 weeks old.

Procedures—Ophthalmic examination of the anterior segment of each eye was performed, including determination of tear film characteristics (Schirmer tear test and tear film breakup time) and corneal sensitivity. Digital photographs of the head and each eye were obtained. Corneal pigmentation of eyes was graded as absent, very mild, mild, moderate, or severe. Signalment and medical history information and American Kennel Club registration status were recorded.

Results—CP was detected in at least 1 eye of 243 of the 295 (82.4%) Pugs; CP was typically very mild or mild. Detection of CP was not significantly associated with coat color, age, eyelid conformation, or tear film characteristics but was significantly associated with sex of dogs. The severity of CP was not significantly associated with American Kennel Club registration status or age, but was significantly associated with sex, tear film characteristics, and coat color. Iris hypoplasia was detected in 72.1% of the Pugs. Iris-to-iris persistent pupillary membranes were detected in 85.3% of the Pugs.

Conclusions and Clinical Relevance—Prevalence of CP in Pugs in this study was high. Unexpectedly high prevalences of iris hypoplasia and persistent pupillary membranes were also identified. The condition identified in these Pugs was a pigmentary keratopathy, rather than pigmentary keratitis or corneal melanosis. This condition may have a genetic basis, and further studies are warranted to determine etiology.

Contributor Notes

Supported by the University of Illinois College of Veterinary Medicine and the Spirit of St. Louis Pug Fanciers Association.

Presented as an oral presentation at the 43rd Annual American College of Veterinary Ophthalmologists Conference, Portland, Ore, October 2012.

The authors thank Drs. Païvi Rajala-Schultz and Mark Mitchell for assistance with statistical analysis, Shari Poruba and Lorri Zoch for technical assistance, and Drs. Kara Escutia and Philippe Labelle for assistance with data collection.

Address correspondence to Dr. Labelle (alabelle@illinois.edu).