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Pigmentary Keratopathy in Pugs | VetGirl Veterinary CE Podcasts

In this VETgirl podcast, we review pigmentary keratopathy in Pugs. About to see a “black” eyeball, and not sure what to do with it? Corneal pigmentation develops secondary to chronic corneal irritation due to primary inflammatory conditions (e.g., pannus), entropion, dry eye, incomplete blinking, aberrant eyelashes, etc. The term pigmentary keratitis  implies that there is inflammation component to the primary corneal disease, which leads to pigmentation. While this diagnosis is made frequently in clinical practice, the primary cause of inflammation is not always identified.

So, Labelle AL et al out of University of Illinois, wanted to study the high prevalence of corneal pigmentation in the Pug breed. While some of the patients had an identifiable underlying corneal inflammatory disease, many Pugs were noted to have corneal pigmentation without an obvious underlying condition. The purpose of this study was to determine the characteristics, risk factors, and prevalence of corneal pigmentation in Pugs. So, they evaluated 295 Pugs in this study, and found the following:

  • Fawn pugs were more likely to have moderate corneal pigment and black pugs were more likely to have mild corneal pigment.
  • Female pugs were more often affected with very mild or mild corneal pigment, whereas male pugs were more often affected with moderate or severe corneal pigment.

Overall, this study found that corneal pigmentation is exceedingly common in Pugs in the United States. This disease likely has a genetic component in this breed. Previously, the pathogenesis of corneal pigmentation in brachycephalic breeds was attributed to chronic corneal irritation from various primary ocular conditions. This study was unable to document a significant association between the presence of corneal pigmentation and these variables in Pugs. Pugs with severe corneal pigmentation had lower Schirmer Tear Test and Tear Film Break Up Time values as compared to Pugs without corneal pigmentation. The authors suspect that the chronic corneal disease may have actually led to the decreased tear production and faster break up time rather than these conditions causing the pigmentation. This hypothesis is supported by their finding that Pugs with very mild, mild, and moderate corneal pigmentation had similar STT and TFBUT values to those Pugs without corneal pigmentation.

Without the presence of an identifiable underlying condition, treatment recommendations for non-inflammatory corneal pigmentation are speculative. The authors of the study routinely treat corneal pigmentation in Pugs with topical immunomodulators such as cyclosporine or tacrolimus. Corneal pigmentation is a very common finding in Pugs and, while all attempts should be made at identifying and treating an underlying cause, this condition may develop as a breed-related phenomenon without a clear inciting cause.

VETgirl’s take on this study? If you do have a Pug and want to preserve their vision, make sure to educate the pet owner on what signs to monitor for and to treat ophthalmic cases aggressively to prevent these secondary changes!

References:

1. Labelle AL, Dresser CB, Hamor RE, et al. Characteristics of, prevalence of, and risk factors for corneal pigmentation (pigmentary keratopathy) in Pugs. J Am Vet Med Assoc 2013;243(5):667-674.1.

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