Abstract
BackgroundProlapsed nictitating membrane gland (PNMG) is the most common disorder of the third eyelid in dogs. However, the epidemiology of PNMG in the wider dog population remains understudied.MethodsUsing de-identified clinical data from the VetCompass Programme, this cohort study aimed to report the prevalence, demographic and breed-related risk factors of PNMG in dogs attending UK primary care veterinary practices in 2016.ResultsThere were 1,802 PNMG cases identified from 905,543 dogs, yielding an annual prevalence of 0.20% (95% confidence interval (CI) 0.19–0.21). The median age at first diagnosis was 0.63 years (IQR 0.33–1.98, range 0.11–18.00). Dogs aged under 1 year had 10.82 times the odds (95% CI 9.17–12.76) compared with dogs aged from 2 to under 4 years. Neutered animals had higher odds than entire animals within both sexes. Breeds with the highest odds of PNMG compared with crossbred dogs included Neapolitan Mastiff (odds ratio (OR) 34.26, 95%CI 15.92–73.75), English Bulldog (OR 24.08, 95% CI 20.62–28.13), Cane Corso (OR 14.66, 95% CI 8.18–26.28), Lhasa Apso (OR 12.37, 95% CI 10.26–14.92) and American Cocker Spaniel (OR 11.57, 95% CI 5.59–23.96). Purebred dogs had 1.43 times the odds (95% CI 1.26–1.63) of PNMG compared with crossbreed dogs. Breeds with brachycephalic skull conformation had 6.71 times the odds (95%CI 5.89–7.64) compared with breeds with mesocephalic skull conformation. Insured dogs had 1.89 times the odds (95% CI 1.65–2.16) compared with uninsured dogs.ConclusionsThis study reports the largest cohort of primary-care PNMG cases assembled to date. The results showing young age at diagnosis along with the breed, purebred and brachycephalic skull conformation predispositions suggest a hereditary involvement in PNMG development. These results may help to guide breeding strategies to reduce the prevalence of PNMG and improve welfare in predisposed individuals.
Highlights
Prolapsed nictitating membrane gland (PNMG), often called “cherry eye”, describes a disorder where the nictitating membrane gland protrudes as a smooth or follicular pink mass from behind the leading edge of the third eyelid
Breeds with the highest odds of PNMG compared with crossbred dogs included Neapolitan Mastiff (odds ratio (OR) 34.26, 95%confidence intervals (CI) 15.92–73.75), English Bulldog, Cane Corso, Lhasa Apso and American Cocker Spaniel
Purebred dogs had 1.43 times the odds of PNMG compared with crossbreed dogs
Summary
Prolapsed nictitating membrane gland (PNMG), often called “cherry eye”, describes a disorder where the nictitating membrane (accessory lacrimal) gland protrudes as a smooth or follicular pink mass from behind the leading edge of the third eyelid (nictitating membrane). Despite affected animals showing few signs of pain in the early stages [4], if left unattended or untreated, PNMG often results in chronic conditions such as keratoconjunctivitis sicca (KCS), inflammation, infection and trauma to the nictitating membrane gland itself, and potential secondary corneal trauma, all of which may result in discomfort or pain [1,2,4,5,6]. In a very small proportion of early and mild cases, topical antibiotic/corticosteroid therapy may be associated with control of the local inflammation and oedema of the conjunctiva, and a return of the nictitating membrane gland to its normal position [7]. Prolapsed nictitating membrane gland (PNMG) is the most common disorder of the third eyelid in dogs. The epidemiology of PNMG in the wider dog population remains understudied
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