Fashionable flat-faced dogs like pugs and French bulldogs may be all the rage among dog lovers, but vets have warned that over-breeding is causing them to go blind, with many not even able to close their eyes. Over-breeding is leading to changes in the dogs’ skull shape, making their eyes bulge, and leaving the surface too exposed. This is causing trauma, ulcers and erosion of the eyeball, leading to vision loss, the researchers said. Many have a condition called macroblepharon , which is an abnormally large opening of the eyelids. This, combined with the way their eyes stick out, often renders them impossible to close. “As these breeds grow in popularity, veterinary hospital teams are treating more and more dogs of brachycephalic [flat-faced] breeds with a wide variety of problems caused by breeding for a characteristic short-nosed flat-face,” the vets said, whose research was published in the Irish Veterinary Journal. For their study, they examined a range of flat-faced breeds, ranging in age from just a few months to aged 16. The breeds, which had been brought to two vet school clinics suffering with eye issues, were French bulldogs, Shih-Tzus, Pugs, English Bulldogs, Boxers, Pekingese and Boston Terriers. Of the 93 dogs studied, nearly half had macroblepharon. The French bulldogs – which, according to Kennel Club figures are the UK’s second favourite dog – were the worst affected by this condition. Entropion – where the eyelid turns inwards so that the eyelashes rub the eyeball – was found in 20 of the dogs, with pugs particularly afflicted. Ulcers on the eyeball’s surface – the cornea – were found in 41 of the pets, and five had them in both eyes, the vets from the University of Lisbon and University of Leipzig discovered. Corneal pigmentation affected 33 of the dogs, with pugs suffering the most. Vision loss occurs as the blackish brown pigment progressively clouds the cornea. Corneal fibrosis, or scarring, affected 23 dogs. Shih Tzus and French Bulldogs were the breeds most likely to have these issues. “The number of these patients is increasing in small animal practices,” said the researchers. “Their personalities, wrinkly faces and appealing large eyes have turned them into popular pets. “This popularity is thought to exist because humans find the large and round eyes, as well as the round face very appealing.” Their study, the vets said, has “highlighted the importance of responsible breeding, early diagnosis and regular ophthalmic check-ups to correctly diagnose, treat and if possible prevent situations of irreversible blindness in these patients”. As well as eye problems, these breeds commonly suffer from breathing issues – a condition known as Brachycephalic Airway Obstructive Syndrome.