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InFocus

A look through the latest literature

The latest academic publications providing further insight into this month’s In Focus topic: ophthalmology

Frequency of and breed-related risk factors for keratoconjunctivitis sicca in UK dogs

Dan O’Neill and others, Royal Veterinary College, Hawkshead, United Kingdom

Keratoconjunctivitis sicca is caused by a deficiency in the aqueous portion of the tear film resulting in irritation of the ocular surface. The authors investigated the frequency of the condition in dogs receiving primary care at practices contributing data to the VetCompass epidemiological research programme. Overall, they found that there were 1,456 cases of keratoconjunctivitis sicca among the 363,898 records examined (0.04 percent prevalence). Breeds with the highest odds ratio for this condition included American Cocker Spaniels, English Bulldogs, Pugs and Lhasa Apsos, while Labrador Retrievers and Border Collies were at a reduced risk. They state that quantitative tear tests during annual health examinations are recommended for dogs of breeds where there is evidence of a predisposition to this condition.

Journal of Small Animal Practice, 62, 636-645

Use of presumed neuroprotective therapies by veterinary ophthalmologists

Ryan Hopper and others, Michigan State University, East Lansing, USA

Degenerative retinal and optic nerve diseases are the most common cause of irreversible sight loss in dogs. Strategies for protecting neurons have been successfully demonstrated in laboratory rodents but there is no proof of their clinical efficacy in humans or companion animals. The authors surveyed members of international veterinary ophthalmology organisations to assess their attitudes towards these therapies. This showed that 85 percent of respondents had used some form of neuroprotective therapy in the past five years despite the lack of published studies. They state that there is a critical need for clinical efficacy data on these methods.

Veterinary Ophthalmology, 24, 229-239

Feasibility of ocular sonography in measuring intracranial pressure in dogs

Adrien Dupanloup and Stephanie Osinchuk, University of Saskatchewan, Saskatoon, Canada

Prompt identification of patients with intracranial hypertension is important to prevent catastrophic consequences such as brain herniation, respiratory failure and death. In human medicine, a useful indicator of raised pressure has been shown to be the ratio of the optic nerve sheath diameter (ONSD) to the eyeball transverse diameter (ETD), measured using ocular ultrasonography. The authors examined the feasibility of this technique in healthy dogs. Their findings show that this is a rapid, reliable and non-invasive method for measuring the ONSD/ETD ratio, which did not appear to be influenced by the morphology of the breed.

American Journal of Veterinary Research, 82, 667-675

Free-living amoebae colonising the cornea of cats with keratitis

Eric Ledbetter and others, Cornell University, Ithaca, USA

Pathogenic free-living amoebae have been shown to be a significant cause of keratitis in human patients, and there is growing evidence that they have a role in feline eye disease. The authors took corneal scrapings from healthy cats and those with naturally acquired keratitis. They found that there was an association between corneo-conjunctival inflammation and the detection of Acanthamoeba species. Another organism, a Naegleria-like amoeba, was also present in some samples but it is not clear that it has any pathological significance.

The Veterinary Journal, 274, 105712

Comparative effects of two topical anti-glaucoma treatments in rabbits

Margaret Li Puma and others, University of Georgia, Athens, USA

Glaucoma is a painful condition causing sight loss in many mammalian species. Similarities in the condition in humans and rabbits suggest that the treatments used in human medicine might be efficacious in rabbits. The authors examined the effects of two such drugs, latanoprost and demecarium, in healthy rabbits. They found that latanoprost increased the iridocorneal angle (ICA) and did not affect intraocular pressure (IOP) while demecarium administration significantly increased IOP and decreased ICA parameters. Therefore, latanoprost may be useful as a glaucoma therapy in rabbits, but demecarium is not recommended.

Journal of Exotic Pet Medicine, 37, 32-38

Cataracts and phacoemulsification in the Siberian Husky

Lisa Uhl and others, Colorado State University, Fort Collins, USA

Cataracts are opacities in the lens and are a leading cause of blindness in dogs. There is a reported incidence of primary cataracts in the Siberian Husky that is three times greater than that in the mixed breed population. The authors compared the characteristics of the cataracts found in Huskies compared with other breeds and the response to phacoemulsification procedures. They found that Huskies evaluated for cataracts were younger and less likely to present with diabetic cataracts than other breeds. There was also evidence for an increased risk of retinal detachment pre- and post-phacoemulsification.

Veterinary Ophthalmology, 24, 252-264

Identification and treatment of orbital apex syndrome in a dog

Jayden Robert and others, Cornell University, Ithaca, USA

Orbital apex syndrome is a condition that is well documented in human medical literature but does not appear to have been described in veterinary literature. Its clinical features include proptosis, ophthalmoplegia, visual deficits and pain affecting the ipsilateral forehead, upper eyelid or cornea. The authors describe a case in a 12-year-old male Cocker Spaniel, caused by a sarcoma in the orbital apex. Surgical resection followed by palliative radiotherapy resolved the clinical signs and the dog was disease-free at 16 months post-treatment.

Canadian Veterinary Journal, 62, 27-31

Gene identified for superficial chronic corneal epithelial defects in Boxers

Kathryn Meurs and others, North Carolina State University, Raleigh, USA

Superficial chronic corneal epithelial defects (SCCEDs) in dogs are lesions that share many characteristics of recurrent corneal erosions in humans. As Boxer dogs are predisposed to this condition, the authors considered it was likely to have a genetic cause. Following a whole genome sequencing analysis, they identified the fault as a deletion in the NOG gene. This codes for a constitutive protein in the cornea that is a potent inhibitor of the BM2 signalling pathway, which appears to regulate the development of limbal epithelial progenitor cells.

BMC Veterinary Research, 17

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