Abstract
ObjectiveTo perform detailed analysis of retinal changes in dogs with SARDS using optical coherence tomography (OCT), funduscopy, and molecular analysis.AnimalsSubjects were 29 dogs from 12 US states and Canada diagnosed with SARDS by 8 ophthalmologists. An additional 7 eyes from 5 deceased SARDS dogs were used for molecular and histological analysis.ProceduresDogs were evaluated using chromatic pupil light reflex testing (cPLR), and electroretinography (ERG); subjects underwent complete ophthalmic examination, including funduscopy, retinal photography, and OCT, in addition to complete laboratory analysis, blood pressure evaluation, abdominal and thoracic radiographs, and computerized tomography (CT) imaging to assess possible systemic abnormalities. Histology and immunohistochemistry analysis was performed in 2 SARDS eyes. Microarray analysis was performed in 5 SARDS retinas.ResultsThirty‐eight percent of patients had <1‐mm wide retinal detachments (RD) on OCT analysis, which could not be detected by funduscopy or retinal photographs. Systemic hypertension did not seem to be a contributing factor (RD 22.2%; ND 20%, Odds ratio = 1.1). No dogs showed neoplastic changes by thoracic or abdominal radiography, or CT imaging. There was no statistically significant difference in age (RD 7.9 ± 1.9 years (mean ± SD); ND 7.6 ± 1.7 years, p = 0.69) or duration of blindness prior to presentation (RD 18 ± 7 days (mean±SD); ND 21 ± 12 days, p = 0.28). Microarray and histology analysis of SARDS eyes revealed molecular changes suggestive of immune‐mediated damage.ConclusionsObserved histological, molecular, and OCT changes are highly suggestive of immune‐mediated damage in SARDS eyes.
Highlights
Eyes were collected for histology analysis from two Sudden Acquired Retinal Degeneration Syndrome (SARDS) patients euthanized within 4 weeks of SARDS diagnosis outside of Iowa State University; patients were diagnosed with SARDS based on the clinical presentation of sudden‐onset blindness, near normal retinal appearance and completely extinguished ERG responses
Sudden Acquired Retinal Degeneration Syndrome was first reported almost four decades ago; the precise etiology of the disease is still being extensively debated without a clear consensus on its exact nature.[1]
SARDS is most frequently seen in middle aged/older females of small breeds, with mixed‐breed dogs, Dachshunds, Pugs, and Miniature Schnauzers being the most frequently affected, which corresponds to our findings in this study.[2,3,24,25]
Summary
Sudden Acquired Retinal Degeneration Syndrome (SARDS) is recognized as one of the most frequent irreversible causes of blindness in the canine population.[1,2,3] SARDS is characterized by sudden‐onset blindness, completely extinguished retinal electrical responses, and abnormal chromatic pupil light reflex (cPLR) properties (no red PLR–good blue PLR).[3,4,5] It has been theorized that SARDs is an autoimmune disease similar to non‐ paraneoplastic autoimmune retinopathies in humans (npAIR), with a strong autoantibody component. Eyes were collected for histology analysis from two SARDS patients euthanized within 4 weeks of SARDS diagnosis outside of Iowa State University; patients were diagnosed with SARDS based on the clinical presentation of sudden‐onset blindness, near normal retinal appearance (vascular attenuation only) and completely extinguished ERG responses. Both patients were euthanized due kidney failure (7‐year‐old castrated male [CM] poodle and 6‐year‐old CM Maltese). Microarray analysis on canine retinal tissue was performed as previously reported.[23] Briefly, 5 eyes from 3 SARDs patients and 5 control eyes from healthy controls without evidence of ocular abnormalities were used for microarray analysis as follows. The odds ratio is the ratio with and without an event in each group; it indicates the probability that an event will occur, divided by the probability that an event will not occur in association with the specific parameter
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