Cofactors associated with Sudden Acquired Retinal Degeneration Syndrome: 151 dogs within a reference population

Comparison of the qualitative and quantitative optical coherence tomographic features between sudden acquired retinal degeneration syndrome and normal eyes in dogs

OBJECTIVE

To quantitatively and qualitatively characterize the retinal optical coherence tomographic features of sudden acquired retinal degeneration syndrome (SARDS) and SARDS suspect dogs.

ANIMALS STUDIED

Fourteen SARDS affected dogs, 11 age-, breed-, and sex-matched control dogs, and two SARDS suspect dogs.

PROCEDURES

Spectral-domain optical coherence tomography (OCT) images were used to evaluate the quantitative features, including thickness, intereye asymmetry, and longitudinal changes in retinal layer thickness and the qualitative features, including retinal architecture and vitreous haze.

RESULTS

Mean outer retinal layer thickness (ORT), outer nuclear layer thickness (ONL), and photoreceptor layer thickness (PRL) were significantly lower in the SARDS group, whereas mean inner retinal layer thickness was significantly higher in the SARDS group than in the control group. While thickness values of all retinal layers did not differ significantly between paired eyes in each group, the absolute intereye asymmetries in the ORT (p < .0001), ONL (p = .008), and PRL (p < .0001) were significantly higher in the SARDS group than in the control group. Some SARDS patients and SARDS suspects had a greater PRL than the control group, and serial OCT evaluation showed an increase in PRL in one SARDS suspect. Vitreous haze severity was greater in the SARDS group than in the control group (vitreous relative intensity, p = .030).

CONCLUSIONS

We described the OCT features of SARDS patients and suspects. In particular, PRL thickening in the SARDS suspects might indicate an early change in SARDS. Although further studies are needed, this finding might provide new insights into the pathogenesis of SARDS.

Canine sudden acquired retinal degeneration syndrome: Owner perceptions on the time to vision loss, treatment outcomes, and prognosis for life

BACKGROUND

Canine sudden acquired retinal degeneration syndrome (SARDS) causes blindness for which there are no proven effective treatments. We aimed to clarify the time to vision loss, treatment response/side effects, and prognosis for life in dogs with SARDS.

METHODS

An online questionnaire was administered to owners of dogs with a historical diagnosis of SARDS. Mortality data were compared with a published purebred reference population. Select parameters were analyzed statistically using general linear model with least square means, two-sample t tests, and chi-squared or Fisher's exact tests.

RESULTS

Responses from owners that stated that their dog visited an ophthalmologist and had electroretinography performed (n = 434) were analyzed. The majority of owners (65.4%) reported the time from vision disturbance to complete vision loss as <2 weeks; 19.4% reported >4 weeks. Onset of systemic clinical signs to complete vision loss was >4 weeks in 44.5% of responses. A higher proportion of owners reported some vision recovery with combination treatment (14.4%) compared with monotherapy (3.2%, P = .0004). Side effects of treatment were commonly reported. Dogs with SARDS did not have a shorter lifespan than the reference population but had higher incidence of kidney disease (P = .0001) and respiratory disease (P = .0004) at death.

CONCLUSIONS

Dogs with SARDS have a rapid onset of vision loss. In the owner's opinion, treatment is unlikely to restore vision and is associated with systemic side effects. The potential for systemic pathologies that arise after SARDS diagnosis warrants further study.

Retinal Diseases of Senior Dogs

Aging consists of a physiological decline of an organism’s functional activity. During the aging process, the structural and functional changes of the retina can be observed. In most cases, progressive vision loss occurs due to the age related changes of the anterior segment. Retinal diseases, characteristic for senior dogs are: retinal detachment, hypertensive chorioretinopathy, sudden acquired retinal degeneration syndrome (SARDS), progressive retinal atrophy (PRA), glaucoma, retinopathy, cystoid degeneration and neoplasms. The examination of the retina in senior dogs is based on: ophthalmoscopic examination, electroretinography, spectral-domain optical coherence tomography (AD-OCT) and if necessary, histopathological examinations. Comprehensive knowledge regarding the senior dog’s health, significantly increases their quality of life.

A modified technique of keratoleptynsis ("letter-box") for treatment of canine corneal edema associated with endothelial dysfunction

PURPOSE

To describe a modified keratoleptynsis procedure, as a method of preserving central corneal function, and evaluate the outcome in vision, reduction of corneal thickness and treatment of epithelial corneal ulcers in cases with endothelial cell dysfunction.

METHODS

Forty-four dogs (72 eyes) were affected by progressive corneal edema, with or without ulcerative keratitis. All patients were treated with a dorsal and ventral superficial keratectomy followed by conjunctival flaps, maintaining a clear central cornea. Corneal thickness measurements were obtained via ultrasound biomicroscopy.

RESULTS

All eyes showed resolution of ocular discomfort postoperatively, with a median time to resolution of 35 days. Two years post-surgery, vision had been lost in 2 of 29 eyes (7%). From the initial population, 23 dogs (39 eyes) had follow-up evaluations of corneal thickness. The mean central corneal thickness was 1359 ± 251 μm prior to surgery. Thickening of the central cornea was observed one week after surgery to 1559 ± 263 μm. Decreased corneal thickness was reported, at 1 month, 4 months, 10 months and 2 years postoperatively (1285 ± 267 μm, 1102 ± 150 μm, 1121 ± 288 μm, 1193 ± 283 μm, respectively). All eyes showed a similar trend of increasing and then decreasing corneal thickness.

CONCLUSIONS

This surgical technique provided statistically significant reduction in central corneal thickness and sustained relief of ocular pain. Reduction in corneal thickness appeared to be maintained 2 years post-surgery, and all patients remained comfortable. Superficial corneal pigmentation and fibrosis resulted in vision loss in two eyes.

Diagnostic utility of clinical and laboratory test parameters for differentiating between sudden acquired retinal degeneration syndrome and pituitary-dependent hyperadrenocorticism in dogs

OBJECTIVE

To identify discriminating factors, using clinical ophthalmic examination findings and routine laboratory testing, that differentiate dogs with early sudden acquired retinal degeneration (SARDS; vision loss <6 weeks' duration), age- and breed-matched control dogs, and dogs with pituitary-dependent hyperadrenocorticism (PDH).

ANIMALS

Client-owned dogs: 15 with SARDS with <6 weeks duration of vision loss, 14 age- and breed-matched control dogs, and 13 dogs with confirmed PDH.

PROCEDURES

Dogs underwent ophthalmic examination, electroretinography (ERG) fundus photography, and spectral-domain optical coherence tomography (SD-OCT) in addition to physical examination, urinalysis, serum biochemistry, complete blood count, and adrenocorticotrophic hormone (ACTH) stimulation testing. Statistical analysis was performed using receiver operating curve area under the curve analysis, principal component analysis with sparse partial least squares analysis, and one-way ANOVA.

RESULTS

Dogs with SARDS all had absent vision and ERG a- and b-waves. SD-OCT demonstrated that dogs with SARDS had significantly thicker inner retina, thinner outer nuclear layer, and thicker photoreceptor inner/outer segment measurements than either controls or dogs with PDH. Discriminating laboratory parameters between dogs with SARDS and PDH with high specificity included post-ACTH serum cortisol (<19.3 μg/dL), AST:ALT ratio (>0.343), and urine specific gravity (>1.030).

CONCLUSIONS AND CLINICAL RELEVANCE

We have identified significant discriminators between SARDS and PDH. This work provides the basis for future studies that could identify and examine dogs with SARDS prior to vision loss, which may extend the potential therapeutic window for SARDS.

Evaluation of the major histocompatibility complex (MHC) class II as a candidate for sudden acquired retinal degeneration syndrome (SARDS) in Dachshunds

Objective

Sudden acquired retinal degeneration syndrome (SARDS) is one of the leading causes of acute blindness in dogs, with an unknown etiology and no effective treatment. Certain breeds such as Dachshunds are overrepresented among SARDS patients, and therefore, the syndrome is suspected to have a genetic component. The objective of this study was to determine if a genetic locus associated with SARDS in Dachshunds could be identified using a genome‐wide association study (GWAS).

Procedures

Genome‐wide association mapping was performed in 15 SARDS‐affected and 16 unaffected Dachshunds. Genotyping of three classical DLA class II genes (DLA‐DRB1, DLA‐DQA1, and DLA‐DQB1) was performed in 34 SARDS‐affected and 66 unaffected Dachshunds to evaluate for an association in this region.

Results

Although no single nucleotide polymorphisms (SNPs) were of genome‐wide statistical significance (P_Bonferroni < 0.05), 5 of the top 9 SNPs were in the major histocompatibility complex (MHC). Using DLA typing, the allele DLA‐DRB1*09401 was identified as a risk factor for the development of SARDS (P = 0.0032, OR = 4.0). The alleles DLA‐DQB1*00101 (P = 0.0050, OR = 0.31), DLA‐DQA1*00901 (P = 0.0087, OR = 0.33), and a previously identified DLA‐DRB1allele described as “DRB1‐T” (P = 0.0284, OR = 0.37) were identified as protective factors.

Conclusions

Although far from definitive, association of SARDS with alleles of immunologic importance further supports the hypothesis that autoimmunity may play a role in the pathogenesis of SARDS.

Optical coherence tomography and molecular analysis of sudden acquired retinal degeneration syndrome (SARDS) eyes suggests the immune-mediated nature of retinal damage

Objective

To perform detailed analysis of retinal changes in dogs with SARDS using optical coherence tomography (OCT), funduscopy, and molecular analysis.

Animals

Subjects 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.

Procedures

Dogs 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.

Results

Thirty‐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.

Conclusions

Observed histological, molecular, and OCT changes are highly suggestive of immune‐mediated damage in SARDS eyes.