A look through the latest literature: ophthalmology - Veterinary Practice
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A look through the latest literature: ophthalmology

A summary of the latest academic publications providing further insight into this month’s spotlight topic of ophthalmology

Increased risk of infected corneal ulcerations in dogs due to smoke exposure

Katrina Jones and others, Colorado State University, Fort Collins

In the autumn of 2020, Colorado experienced the two largest wildfires in the state’s history. Smoke blanketed the town of Fort Collins and produced an air quality index above 100 on several days, indicating a high risk of smoke-related ill health, particularly in sensitive groups of people. The authors investigated the effects of smoke exposure on the local dog population. Their results show a significantly elevated risk of infected corneal ulcers in dogs in late 2020 compared with the previous two years when the air quality was normal. They suggest that the effects of wildfires on domestic animals should be investigated further as the frequency and duration of such incidents continue to increase around the world.

Veterinary Ophthalmology, 25, 240-259

Outcomes in dogs receiving rhexis-fixated prosthetic intraocular lenses

Gary Lewin and Chris Dixon, Veterinary Vision, Penrith, Cumbria

Prosthetic endocapsular intraocular lenses (IOLs) are available for use in dogs with cataracts that are undergoing surgery to remove the affected lens; however, these devices may not be suitable in cases where the capsule is damaged. The authors have developed a method for inserting a lens that allows fixation across the anterior and/or posterior capsulorhexes in cases where an endocapsular IOL is not appropriate. The outcomes in 30 dogs that underwent the rhexis fixation procedure are described. In 26 cases, the eyes were functional at 3 to up to 76 months’ follow-up.

Journal of Small Animal Practice, 63, 211-219

Development of a tool for recognising ocular pain in horses

Flaminia Ortolani and others, University of Perugia, Italy

Horses with painful conditions will exhibit characteristic behavioural changes, but these rarely provide information on the source or severity of the discomfort. The authors have developed a composite pain scale intended for the analysis of ophthalmic pain in horses. They describe a study to validate the Equine Ophthalmic Pain Scale (EOPS) using assessments by seven masked observers of videos which showed eight horses with ocular or adnexal diseases and 15 healthy animals. Sensitivity and specificity in identifying horses with ocular pathology were 83 percent and 100 percent, respectively.

The Veterinary Journal, 278, 105774

Multimodal ocular imaging of corneal stromal disorders in dogs

Sangwan Park and others, University of California, Davis

A range of conditions may affect corneal transparency in veterinary patients, although the resulting opacity may be undetectable until it has reached a critical size. The authors investigated the use of two imaging methods as aids to the early detection of corneal stromal disorders: Fourier-domain optical coherence tomography and in vivo confocal microscopy. They found that in vivo multimodal corneal imaging does facilitate instantaneous microstructural analysis and may be valuable in the differential diagnosis of these conditions. However, the non-specific nature of their findings means that other diagnostic methods will also need to be used in such cases.

BMC Veterinary Research, 18, 117

Feline ophthalmomyiasis externa caused by Cuterebra larvae

Brittany Schlesener and others, Cornell University, Ithaca, New York

Ophthalmomyiasis describes infestations of the eye with the larvae of a group of dipteran flies commonly known as bots. A few cases have been described in dogs and cats, but there have been no previous reports in cats specifically involving larvae of Cuterebra species, which usually infests small mammals. The authors examined the clinical records from their hospital between 2005 and 2020; they found four cases of Cuterebra ophthalmomyiasis. All were in young cats under three years old examined in the summer months. In two cases, the nictitating membrane was infected, and two had orbital disease. Successful larval removal was carried out in each case.

Journal of Feline Medicine and Surgery, 24, 189-197

Comparison of single and triplicate intraocular pressure measurements in dogs

Kathryn Diehl and others, University of Georgia, Athens

Tonometry is a common diagnostic technique in veterinary practice used to investigate changes in intraocular pressure as a result of conditions such as uveitis and glaucoma. The authors investigated the variation seen between the results of single and triplicate applanation tonometry values in healthy dogs. They found no clinically meaningful difference between the first, lowest and averaged triplicate IOP measurements, but the first reading has a larger variance and hence will result in lower statistical power.

American Journal of Veterinary Research, 84, 349-355

Effects of long-term melatonin administration on ocular function in dogs

Claudia Gianetto and others, University of Messina, Italy

Melatonin is a neurohormone shown to be involved in several physiological processes in the human eye, such as dark adjustment, aqueous production, modulation of intraocular pressure and wound healing. Studies in other species have suggested that melatonin may have possible applications in the treatment of glaucoma in dogs. The authors investigated the effects of long-term (30 days) oral administration in healthy dogs at a dose of 0.3mg/kg. They found that treatment had no significant effects on tear production, intraocular pressure or serum melatonin concentrations.

Journal of the American Veterinary Medical Association, 250, 524-529

Squamous cell carcinoma of the nictitating membrane and gingiva in a cat

John Munday and others, Massey University, Palmerston North, New Zealand

Papillomaviruses are DNA viruses that generally infect epithelial tissue and have been associated with squamous cell carcinomas (SCCs) of the mouth and cervix in humans. The authors describe a case in which Felis catus papillomavirus type 3 was isolated from SCCs affecting the nictitating membrane and gingiva of an 11-year-old male domestic shorthair. This appears to be the first report of a papillomavirus-associated malignancy in this species. They suggest that this pathogen should be considered as a potential cause of tumours affecting mucosal surfaces in cats.

Veterinary Pathology, 59, 463-466

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