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Subedited by Dr Phil Tucak
Sudden acquired retinal degeneration syndrome (SARDS) is an idiopathic disease of adult dogs associated with acute onset of blindness, usually over the course of days to weeks. There is no known breed predisposition or associated cause, and while cases are often detected seasonally (in the latter half of the year in Australia), the significance of this is also unknown. This case report describes an acute onset of SARDS in an adult dog.
Ruby-Tuesday is a nine-year, eight-month-old labradoodle who presented for assessment of possible blindness and dribbling of urine in September 2021. The patient had an extensive history of otitis externa and spinal osteoarthritis. Treatment of a bout of otitis externa had been completed two weeks prior to presentation via use of a weekly dosed topical gel consisting of florfenicol, terbinafine and betamethasone acetate (Osurnia).
Extensive workup including blood screen (revealing a slight elevation in SDMA) and radiographs under sedation was undertaken in the prior month for investigation of urination when excited, polydipsia, osteoarthritis and a cough. Pertinent ocular history involved an acute onset, suspect allergic conjunctivitis treated with topical antibiotics and anti-inflammatories (Amacin Eye and Ear ointment) five weeks prior to the visit.
On presentation, the owner reported inflammation of the dog’s right eye and difficulty with vision, which had been pronounced over the previous three days, though this may have been present in a less defined manner prior to this. The owner noticed the dog displaying hesitance navigating around objects and that she had been tripping over objects in her path. The owner also advised dribbling urine had been a persistent issue with Ruby-Tuesday.
General clinical examination was largely unremarkable, with scant dental calculus and resentment on lumbar palpation consistent with osteoarthritis. Ocular examination confirmed marked vision deficits with an inability to navigate obstacles and difficulty in identifying the location of food rewards in the consult.
A menace response was absent and the pupillary light response was sluggish to respond in both eyes. Cataract development was present bilaterally. Retinal examination was unremarkable. The left eye only exhibited mild scleral injection with mild to moderate conjunctivitis. Both eyes were negative on fluoroscein staining. Tonometry yielded a measurement of 20mmHg in the left eye and 26mmHg in the right. Urinalysis of a free catch urine sample was unremarkable apart from mild alkalinity.
The primary differential given the presenting clinical signs and lack of ocular findings to explain vision loss was SARDS. Referral to a local veterinary ophthalmology specialty centre was advised to confirm the diagnosis, and was undertaken on the same day. Ocular testing was repeated and coloured pupillary light responses were assessed, yielding no response to red light and a middle to complete response to blue light.
The specialist agreed SARDS was the primary differential for the acute vision loss. A confirmatory electroretinogram was not undertaken.
Follow-up examinations over the subsequent two months showed the patient tolerating blindness very well and minimal impairment to quality of life.
Unfortunately, with an unknown aetiology and mechanism, vision loss associated with SARDS is deemed permanent at this time. There is no treatment indicated though regular health checks are advised. Prognosis for quality life is excellent with sufficient client education as to how to accommodate a dog with impaired vision, such as maintaining a consistent environment.
While at this time SARDS remains a truly idiopathic disease, there is an association between development of signs attributable to Cushing’s disease and the onset of vision loss. The disease has a predilection for middle aged, spayed female dogs, similar to Cushing’s disease (though lacks an established breed predisposition).
The signalment of the patient in this case is consistent with this observation, especially with the signs of polydipsia and inappropriate urination. Blood screen performed a month prior to presentation for vision loss did not show any pathological changes consistent with hyperadrenocorticism, but this could not be ruled out without more specific disease testing such as a low dose dexamethasone test or adrenocorticotropic hormone stimulation test.
Urine was well concentrated (USG 1.034), which is inconsistent with Cushing’s disease in this case. The timing of presentation in September matches the observed seasonality of the disease.
Interestingly, cushingoid signs have been reported to resolve in dogs who then go on to develop SARDS, either associated with the onset of vision loss or subsequently. At the time of follow-up two months later, urinary leakage was a persistent issue in the patient. A treatment trial for hormone responsive urinary incontinence was discussed with the owner, but has not yet been pursued.
While SARDS was confirmed to be the primary differential in this case via specialist assessment, other differentials for acute vision loss include optic neuritis and central (brain) lesions. Confirmation of SARDS is via electroretinogram, but given the specialised nature, expense, and invasiveness of this testing, it is not frequently pursued, as was consistent in this case.
SARDS should be considered as a primary differential for acute cases of vision loss in the absence of associated ocular signs, especially in dogs with a reported history of urinary issues and other cushingoid presentations in the Australian spring season. While vision loss is permanent, prognosis for quality life is excellent with owner commitment.
The author wishes to thank the patient’s owners, and the staff of Animal Eye Care Victoria for their prompt acceptance of the case, advice and ongoing guidance.
Dr Belinda Oppenheimer BVSc (Hons) MANZCVS
Dandenong Ranges Veterinary Centre
Dr Belinda Oppenheimer has been loving life in the Dandenong Ranges after moving there in 2020. She has a passion for welfare medicine and has several years’ experience working in animal shelters.
Dr Oppenheimer also has a love for the unusual, gaining her MANZCVS qualification in Medicine and Surgery of Unusual Pets in 2019, so she is always keen to see rabbits, guinea pigs, reptiles, birds and other special little friends.
Komaromy, AM et. al. 2016. Sudden acquired retinal degeneration syndrome (SARDS) – a review and proposed strategies toward a better understanding of pathogenesis, early diagnosis, and therapy. Veterinary Ophthalomology 19;4:319-331.
Ofri, R. 2008. Retina. In: Slatter’s Fundamentals of Veterinary Ophthalmology. Saunders Elsevier, St. Louis.
Personal communication, Animal Eye Care, Victoria.
Hoffman, JM et. al. 2018. Canine hyperadrenocorticism associations with signalment, selected comorbidities and mortality within North American veterinary teaching hospitals. J Small Anim Pract 59;11:681-690.