Unilateral invasive intraocular melanoma with choroidal and optic nerve involvement resulting in bilateral vision loss in a Labrador Retriever.

A 10-year-old male castrated Labrador Retriever cross was referred for evaluation of acute vision loss. Ophthalmic examination revealed mild left sided exophthalmos, bilateral resting mydriasis, an absent direct and reduced consensual PLR in the left eye and reduced direct and absent consensual PLR in the right eye. Examination of the cornea and anterior segment with slit lamp biomicroscopy was unremarkable. Indirect fundoscopy revealed a left optic nerve head obscured by a darkly pigmented lesion. Fundic examination in the right eye was unremarkable. Magnetic resonance imaging revealed a smoothly marginated, lobulated cone to irregularly shaped, strongly T1 hyperintense, T2 and T2 fluid-attenuated inversion recovery hypointense, strongly contrast enhancing mass closely associated with the entire left optic nerve, extending across the optic chiasm and into the right optic nerve ventrally. Full clinical staging revealed no evidence of metastasis. Exenteration of the left eye was performed. Histopathology revealed an unencapsulated, poorly demarcated, multilobulated and infiltrative pigmented mass that was effacing the posterior choroid and optic nerve. The mass was composed of a moderately pleomorphic population of heavily pigmented polygonal cells arranged in sheets and clusters, displaying moderate anisocytosis and anisokaryosis. The population of cells contained moderate amounts of abundant brown-black granular pigment consistent with melanin within the cytoplasm. Mitotic figures averaged approximately three per ten 400× fields (2.37 mm2 ). This is the first report of a melanocytic tumor invading along the optic nerve and tract to result in contralateral vision loss.

Sports ball projectile ocular trauma in dogs.

OBJECTIVE: To describe the clinical features, management, and outcome of dogs presenting with sports ball projectile ocular injuries. ANIMALS STUDIED: Eighteen dogs. PROCEDURES: A retrospective study reviewing cases of ocular injury due to a sports ball projectile that presented to the Cornell University ophthalmology service between 2004 and 2021. Dog age, type of sports ball, initial ocular lesions, eye affected, clinical management, and visual outcome were recorded. RESULTS: Sports ball projectile ocular injuries were identified in 18 eyes of 18 dogs. The median age of the dogs was 1.0 years old, ranging from 0.3- to 9-years- old. Nine dogs were male, and 9 were female. Ocular injuries were caused by small, dense balls (e.g., golf balls, baseballs) in 11 dogs; small, light balls (e.g., tennis balls, toy balls) in 5 dogs; and large, soft balls (e.g., soccer ball, football) in 2 dogs. Closed-globe injuries (12 of 18 eyes) presented with traumatic uveitis (91%), hyphema (45%), and subconjunctival hemorrhage (18%). All 12 closed-globe injury cases were medically managed, eight dogs remained visual. Open-globe injuries (6 of 18 dogs) presented with three corneal lacerations and three scleral ruptures. Five open-globe injuries required enucleation, and one was medically managed and maintained vision. CONCLUSION: Sports ball projectile ocular injuries in dogs can result in substantial ocular morbidity and in loss of vision. Small, dense balls were associated with injuries that carried the most guarded prognosis and required more aggressive management. Small and large lighter projectiles were associated with less serious ocular injuries and visual outcomes.

Risky business: influence of eye flukes on use of risky microhabitats and conspicuousness of a fish host.

A prerequisite for a parasitic manipulation to be considered adaptive is that it confers a fitness benefit to the parasite, such as increased transmission to another host. These manipulations can involve alterations to a wide range of host phenotypic traits, including microhabitat choice. Eye flukes of the trematode family Diplostomidae use fish as intermediate hosts and must be transmitted by predation to a piscivorous bird. In New Zealand, the diplostomid Tylodelphys darbyi infects the eyes of a widespread endemic freshwater fish, the common bully Gobiomorphus cotidianus. Within the eye, T. darbyi metacercariae achieve large sizes and move freely about the aqueous and vitreous humors of the eye. We hypothesized that higher intensities of T. darbyi would (i) cause bullies to show increased activity and spend more time moving about in open space (i.e., more conspicuous, risky microhabitat) and (ii) reduce their ability to compete for shelter with fish harboring lower infection levels. Our experiments showed that heavily infected fish were more active and spent more time in the open, although the effect was age-dependent, with immature fish displaying decreases in activity and time spent in the open with increasing intensities of infection. We also demonstrated that heavily infected female bullies have a lower probability of using shelter, but males show the opposite pattern. It is possible that using more risky microhabitats increases the likelihood of the fish being eaten by the parasite's predatory avian definitive hosts. However, our findings indicate that age- and sex-dependent effects call for a more nuanced interpretation.

Genetics of Equine Ocular Disease.

Horses perform in a variety of disciplines that are visually demanding, and any disease impacting the eye has the potential to threaten vision and thus the utility of the horse. Advances in equine genetics have enabled the understanding of some inherited ocular disorders and ocular manifestations and are enabling cross-species comparisons. Genetic testing for multiple congenital ocular anomalies, congenital stationary night blindness, equine recurrent uveitis, and squamous cell carcinoma can identify horses with or at risk for disease and thus can assist in clinical management and breeding decisions. This article describes the current knowledge of inherited ocular disorders.

Development of a vision impairment score for the assessment of functional vision in dogs: Initial evidence of validity, reliability, and responsiveness.

AIM: To describe the development and initial validation of a questionnaire measuring functional vision in dogs. METHODS: A 17-item survey was designed to quantify functional vision in dogs. The Vision Impairment Score (VIS) was determined by summing responses to each question. Questions were assigned to one of five subcategories: overall vision, daily activities, peripheral vision, near vision, and distance vision. Content validity was established during development phases, and construct validity via comparing results of known groups (blind vs sighted; normal vs impaired vision; surgery to improve vision vs nonrestorative surgery), and through factor analysis. Concurrent criterion validity was determined with use of a validated health-related quality-of-life (HRQL) assessment tool. Reliability and responsiveness assessments were investigated using intraclass correlation coefficient (ICC) and effect size (ES), respectively. RESULTS: Responses (221) from 201 dog owners were included. Compared to sighted dogs (n = 153), blind dogs (n = 48) had a higher VIS and greater impairment in all subcategories. Among sighted dogs, a higher VIS was obtained in dogs with low vision compared to those with normal vision (P < 0.001). A higher VIS was associated with poorer HRQL (P < 0.001). Perfect reliability was obtained for 6/17 questions, and excellent reliability for 11/17 questions (intraclass correlation 1.0 and >0.9, respectively), and the VIS was highly responsive to therapeutic intervention (effect size 1.46). CONCLUSION: Results suggest the VIS may be clinically useful in assessing and obtaining a quantifiable measure of functional vision in dogs. Ongoing validation of the tool for clinical use is needed.

Technique, postoperative complications, and visual outcomes of phacoemulsification cataract surgery in 21 penguins (27 eyes): 2011-2015.

OBJECTIVE: To describe surgical technique, postoperative complications, and visual outcome in penguins after phacoemulsification lens extraction surgery. ANIMALS STUDIED: Twenty-one penguins (27 eyes) that had phacoemulsification from 2011 to 2015 at Animal Eye Associates. Species included are as follows: 14 southern Rockhopper (18 eyes, 66.6%), 4 Gentoo (4 eyes, 19%), 2 King (3 eyes, 9.5%), and 1 Chinstrap penguin (2 eyes, 4.8%). Eleven of the penguins were females, and 10 were males with average age at the time of surgery being 27.5 years (range of 22-31 years). PROCEDURE: This is a retrospective study of phacoemulsification cataract surgery patients from 2011 to 2015. Visual outcome was evaluated by veterinary ophthalmologists at postoperative recheck examinations and subjectively by penguin keepers using individual bird surveys and paired t tests for statistical analysis. RESULTS: All eyes were functionally visual after surgery and at the time of last follow-up. Based on keeper surveys, 81% (17/21) of penguins showed immediate improvements in overall quality of life and 90% (19/21) of penguins exhibited improvement in mobility and behavior within their exhibit following cataract removal. Of the 14 penguins that received 1:5 intracameral atracurium during surgery, 10 (71.4%) had moderate mydriasis, 1 (7.1%) had minimal mydriasis, and 3 (21.4%) showed no effect to the pupil. Seventy percent of the cases had phacoemulsification times less than 60 seconds/eye; the mean time was 72 seconds. Sixteen eyes (59.3%) underwent anterior capsulotomy only, planned anterior and posterior capsulotomies were performed in 3 eyes (11.1%), and the entire lens capsule was removed due to capsular fibrosis and wrinkling in 8 eyes (29.6%). The most common short-term postoperative complication was temporary mild blepharospasm and/or epiphora, reported in 8 eyes (29.6%) from 7 penguins (33.3%). Long-term complications, 2-6 years postoperatively, included posterior synechiation resulting in dyscoria (10 of 24 eyes, 41.7%) and capsular fibrosis in all penguins with residual lens capsule (19/19, 100%). CONCLUSION: The prognosis for vision and behavioral improvement after phacoemulsification surgery in penguins is good, with low incidence of vision-threatening complications.

Development and validation of the canine visual function instrument.

OBJECTIVE: In this study, we created the Canine Visual Function Instrument (CVFI) and tested its validity and reliability for assessing the quality of vision of dogs. METHODS: We used Cronbach's alpha to test the strength of the consistency of the questions in the instrument and factor analysis to assess whether the questions achieved unidimensionality in the measurement of dogs' vision quality. RESULTS: Our analysis shows that the CVFI is a valid and reliable tool to seek self-reported observations about dogs' vision quality from owners. Our results also show that the vision quality scale has high empirical validity and therefore can be used to determine whether a dog has normal vision or moderate or serious visual impairments. CONCLUSION: The CVFI might have important practical applications in the field of veterinary ophthalmology in two important ways. First, it can be used to determine whether the treatment of dogs with visual impairment improves vision quality. Second, it can be used as a warning system to alert owners about their dogs' quality of vision.

Electroretinographic findings in day-blind dogs.

Cone degeneration (cd; day blindness) is one of the inherited retinal diseases of dogs. Its diagnosis is based on vision testing, fundoscopy, electroretinography (ERG) and, for some breeds, on genetic tests. Typical signs of the disease are day blindness and cone dysfunction during ERG while fundoscopy does not show any abnormalities. The aim of this study was to compare behavioural findings, fundoscopic lesions and electroretinographic alterations in 12 cd-affected dogs (Alaskan Malamute, Labrador Retriever, German Shepherd, Dachshund, Yorkshire Terrier, Shih Tzu, Siberian Husky and crossbreeds) examined at our clinic. None of the examined dogs had any fundoscopic lesions, and all of them had normal scotopic vision with strongly impaired or absent photopic vision. Light-adapted transient, cone-mediated and steady-state, 31-Hz cone flicker ERGs were much below the 5th percentile limits of normality or even unrecordable, while the rod-driven ERGs were within normal values. Vision test and ERG results corresponded to each other and, combined with the results of fundoscopy, were typical of cd. To date, our research is one of the few studies in the world presenting ERG alterations compared with vision test findings and fundoscopic results in the course of cd.

Restored vision in a young dog following corticosteroid treatment of presumptive hypophysitis.

BACKGROUND: Hypophysitis is an umbrella term for a group of disorders involving inflammation of the pituitary gland. A rare occurrence in humans, hypophysitis can produce a range of clinical signs including (but not limited to) visual deficits and diabetes insipidus. Only five cases of canine hypophysitis exist in the literature, all presenting in mature dogs with no visual deficits and a grave outcome. This case report describes the clinical and advanced imaging features of blindness-inducing presumptive hypophysitis in a dog, which rapidly resolved with medical management. CASE PRESENTATION: A 1-year-and-seven-month-old neutered male Standard Poodle presented with subacute blindness, ataxia, and polyuria/polydipsia (PUPD). Magnetic resonance imaging (MRI) detected a contrast-enhancing pituitary mass with perilesional oedema compromising the optic chiasm. Suspecting neoplasia, anti-inflammatory corticosteroid was commenced prior to radiation therapy planning. Complete resolution of neurological and visual deficits occurred within 12 days of starting steroid treatment. Repeated advanced imaging indicated macroscopic resolution of the lesion. An extended thyroid panel with insulin-like growth factor-1 analysis supported a diagnosis of hypophysitis. Resolution of PUPD was achieved with tapering courses of prednisolone and desmopressin; the dog has since been clinically normal for 14 months and treatment-free for 11 months. CONCLUSIONS: To the authors' knowledge, this is the first instance in which a canine pituitary mass has demonstrated long-term resolution with palliative medical treatment alone, alongside reversal of associated blindness and presumptive diabetes insipidus. We suspect this lesion to be a form of hypophysitis, which should be included among differential diagnoses for pituitary masses, and for subacute blindness in dogs. Where possible, we advocate biopsy-confirmation of hypophysitis prior to timely intervention with anti-inflammatory treatment.

Retrospective evaluation of phacoemulsification and aspiration in 41 horses (46 eyes): visual outcomes vs. age, intraocular lens, and uveitis status.

OBJECTIVE: To determine the effect of age at the time of surgery, intraocular lens (IOL) placement, and presence of chronic uveitis on visual outcome after phacoemulsification and aspiration (PA) of cataracts in horses. ANIMALS STUDIED: Records of 41 horses (46 eyes) receiving unilateral or bilateral PA. METHODS: Retrospective analysis of horses receiving unilateral or bilateral PA at the NCSU-VTH (35 horses, 39 eyes) and in Northern Italy (six horses, seven eyes) was performed. Visual status at last follow-up was compared to age at the time of surgery, IOL status, and presence of chronic uveitis preoperatively. Seven horses with chronic uveitis also underwent placement of a suprachoroidal cyclosporine implant. Clinical ophthalmic examinations and owner questionnaires were used to evaluate visual status. RESULTS: Twenty-one of 46 eyes (46%) received an IOL and 12 of 46 eyes (26%) had chronic uveitis. Overall, 25 of 46 eyes (54%) were visual at last follow-up (mean 35.1 ± 34.8 months). Age (mean 8.6 ± 7.7 years) was not significantly associated with visual outcome. Fourteen of 21 (67%) pseudophakic eyes and 11 of 25 (44%) aphakic eyes were visual at last follow-up (P = 0.342). Eyes with preoperative chronic uveitis were significantly less likely to be visual (3 of 12 eyes [25%]) than horses without preoperative chronic uveitis (22 of 34 eyes [65%]) (P = 0.023). CONCLUSIONS: Horses with chronic uveitis had significantly less favorable visual outcome after PA. Older age at surgery and IOL use were not associated with poor visual outcome.

Visual outcomes of phacoemulsification cataract surgery in horses: 1990-2013.

OBJECTIVE: To evaluate the long-term visual outcome of phacoemulsification lens extraction surgery in foals and horses and identify any unique postoperative complications that affect the visual outcome. PROCEDURE: This is a retrospective medical records study of phacoemulsification cataract surgery in 95 foals and horses from 1990 to 2013. RESULTS: Cataracts were removed by phacoemulsification from 111 eyes of 95 horses ranging in age from 22 days to 26 years (average 8.0 ± 5.7 years). Forty-four of the 95 animals were foals (46.3%). Sixteen horses or foals had surgery bilaterally. One hundred and two eyes were blind preoperatively with 97 eyes (95.1%) having evidence of vision immediately postoperatively. Ninety of the 95 horses (94.7%) regained vision in the immediate postoperative period. Five horses did not recover vision postoperatively. Twenty-four horses had cataracts associated with equine recurrent uveitis (ERU). Trauma was noted as the cause of cataract in 10 horses, and no specific cause for the cataract identified in 61 horses. The combined visual outcome data from horses with all types of cataracts (n = 95) found 83 (87.3%) horses to be visual ≤1 month postoperatively, 47 (49.4%) horses visual for >1-6 months postoperatively, 33 (34.7%) horses visual from >6 to 12 months postoperatively, and 25 horses (26.3%) visual >24 months postoperatively. CONCLUSION: The results of phacoemulsification cataract surgery in horses indicate at least 26.3% of horses are still visual and able to continue their natural activity for 2 years or more postoperatively.

Dual sensory impairments in companion dogs: Prevalence and relationship to cognitive impairment.

PURPOSE: Many older dogs (Canis lupus familiaris) develop cognitive impairment. Dog owners often describe impairments in multiple sensory functions, yet the relationships between sensory and cognitive function in older dogs is not well understood. METHODS: We performed assessments of dog vision and hearing, both clinically (n = 91, electroretinography and brainstem auditory evoked potential) and via validated questionnaire (n = 238). We determined prevalence of sole and dual hearing/vision impairments in younger (<8 years) and older (≥8 years) dogs. Impairment cutoffs were determined using data from young dogs. We assessed the relationships between questionnaire-assessed vision and/or hearing impairments and cognitive impairment using logistic regression. RESULTS: Younger and older dog groups had similar distributions of sex and purebred/mixed breed status. Sex had no relationship to prevalence of sensory impairments. Older dogs had higher prevalence of hearing, vision, and dual sensory impairments, assessed both clinically and by questionnaire (P<0.001), and cognitive impairment assessed by questionnaire (P<0.001). Dogs had higher prevalence of reported cognitive impairment when owners reported dual vision and hearing impairments (79-94%, versus 25-27% in dogs with no sensory impairments), which was most consistent in dogs aged ≥8 years. In these older dogs, dual vision/hearing impairments were associated with a significantly increased risk of cognitive impairment (1.8-2.0 odds ratio). CONCLUSION: Dogs aged ≥8 years are at higher risk for dual hearing/vision impairments and associated cognitive impairments. The causal relationship between these impairments is not defined, but clinical consideration of these multimorbidity risks should be made in older dogs.

Diagnosing Corneal Pigmentation in Small Animals.

The transparency of the cornea is critical to its role in transmitting light. Loss of corneal transparency results in visual impairment. Corneal pigmentation results from melanin accumulation in the epithelial cells of the cornea. Differential diagnosis for corneal pigmentation include corneal sequestrum, corneal foreign body, limbal melanocytoma, iris prolapse, and dermoid. These conditions must be excluded to reach a diagnosis of corneal pigmentation. A myriad of ocular surface conditions are associated with corneal pigmentation, including qualitative and quantitative tear film deficiency, adnexal disease, corneal ulceration, and breed-related corneal pigmentation syndromes. Accurate etiologic diagnosis is critical to determining effective treatment.

Detailed functional and structural characterization of a macular lesion in a rhesus macaque.

PURPOSE: Animal models are powerful tools to broaden our understanding of disease mechanisms and to develop future treatment strategies. Here we present detailed structural and functional findings of a rhesus macaque suffering from a naturally occurring bilateral macular dystrophy (BMD), partial optic atrophy and corresponding reduction of central V1 signals in visual fMRI experiments when compared to data in a healthy macaque (CTRL) of similar age. METHODS: Retinal imaging included infrared and autofluorescence recordings, fluorescein and indocyanine green angiography and spectral domain optical coherence tomography (OCT) on the Spectralis HRA + OCT platform. Electroretinography included multifocal and Ganzfeld-ERG recordings. Animals were killed and eyes analyzed by immunohistochemistry. RESULTS: Angiography showed reduced macular vascularization with significantly larger foveal avascular zones (FAZ) in the affected animal (FAZBMD = 8.85 mm(2) vs. FAZCTRL = 0.32 mm(2)). OCT showed bilateral thinning of the macula within the FAZ (total retinal thickness, TRTBMD = 174 ± 9 µm) and partial optic nerve atrophy when compared to control (TRTCTRL = 303 ± 45 µm). Segmentation analysis revealed that inner retinal layers were primarily affected (inner retinal thickness, IRTBMD = 33 ± 9 µm vs. IRTCTRL = 143 ± 45 µm), while the outer retina essentially maintained its thickness (ORTBMD = 141 ± 7 µm vs. ORTCTRL = 160 ± 11 µm). Altered macular morphology corresponded to a preferential reduction of central signals in the multifocal electroretinography and to a specific attenuation of cone-derived responses in the Ganzfeld electroretinography, while rod function remained normal. CONCLUSION: We provided detailed characterization of a primate macular disorder. This study aims to stimulate awareness and further investigation in primates with macular disorders eventually leading to the identification of a primate animal model and facilitating the preclinical development of therapeutic strategies.

Symblepharon secondary to ophthalmomyiasis externa in a dog.

A 4-month-old crossbred female dog presented with complaints of poor vision and odd appearance of the eyes. At the age of a month, the animal was found lying in a railway road in a very bad condition and was rescued from death. At that time, the patient was presented with severe bilateral ocular discharge, and from both eyes, dipterous fly larvae were extracted. The dog was given symptomatic treatment (deworming, topical and systemic antibiotics, nutritional support) but never regained a normal eye appearance. At the time of the initial presentation, it had severe vision impairment because of bilateral cicatricial symblepharon, total in the left eye and occupying 3/4 of the cornea in the right eye. Surgery was proposed to attempt a resolution. Superficial keratectomy was performed in both eyes. After a midline incision in the cornea, the conjunctiva was dissected away. The conjunctiva was apposed to and sutured to the limbus and secured in the upper and lower conjunctival fornix. Additionally, in the left eye, a lateral canthotomy and canthoplasty were performed to enlarge the size of the eyelid opening. The corneal epithelium healed without complications, the patient regained vision, and after 36 months of follow-up, no recurrences were observed. To the authors' knowledge, this is the first report of symblepharon secondary to ophthalmomyiasis externa in a dog.

A mutation in gene CNGA3 is associated with day blindness in sheep.

Lambs with congenital day blindness show diminished cone function, which is characteristic of achromatopsia, a congenital disorder described in humans and dogs. To identify gene(s) associated with sheep day blindness, we investigated mutations in the CNGA3, CNGB3, and GNAT2 genes which have been associated with achromatopsia. Sequencing the coding regions of those genes from four affected and eight non-affected lambs showed that all affected lambs were homozygous for a mutation in the CNGA3 gene that changes amino acid R236 to a stop codon. By PCR-RFLP-based testing, homozygosity for the stop codon mutation was detected in another 19 affected lambs. Non-affected individuals (n=386) were non-carriers or heterozygous for the mutation. While a selection program has been launched to eradicate the day blindness mutation from Improved Awassi flocks, a breeding nucleus of day-blind sheep has been established to serve as animal models for studying human achromatopsia.

An Observational Study of the Behaviour of Captive Rehabilitant Sun Bears (Helarctos malayanus).

Rehabilitant Malayan sun bears often remain in captivity for long periods of time and may experience significant welfare challenges including disability and persistent lip lesions. This study aimed to investigate whether short-term observations of behavior such as oral stereotypies are useful as noninvasive indicators of lip lesion pain, and whether behavior differs between able-bodied and disabled bears. Observations were collected from 21 captive, rehabilitant Malayan sun bears, of both sexes, a range of ages, and with lip lesions ranging in severity. Some also had disabilities.Oral stereotypy frequency was unrelated to lip lesion severity (p > 0.05), and no relationships with other behaviors were found; however, visual disabilities had significant effects on behavior. For example, visually disabled bears walked more than able-bodied bears (p = 0.003) or those with physical disabilities (p = 0.01). Further research on the feeding behavior of bears suffering from lip lesions may elucidate other potential behavioral indicators of pain. Researching effects of visual disabilities in bears with a larger sample size is also recommended to determine generalizable impacts in affected individuals and resulting welfare implications.

Abnormal visual resolution in the Siamese cat.

When tested behaviorally, Siamese cats display marked differences in contrast sensitivity compared to ordinary cats. Overall sensitivity is depressed, the high-frequency cutoff point is lower, and there is less falloff in sensitivity at low spatial frequencies. Optical factors may contribute to these differences, or they may be attributable to the well-established anatomical abnormalities within the visual system of the Siamese cat.

The Dominant white mutation in the PMEL17 gene does not cause visual impairment in chickens.

OBJECTIVE: To examine whether the Dominant white mutation (causing a hypopigmented phenotype in chicken) affects the visual ability and gives rise to ocular abnormalities in chickens (Gallus gallus). PROCEDURE: Chickens homozygous for either the Dominant white mutation or the wild-type alleles were tested in a visual contrast behavioral test and subjected to histological and ophthalmologic examination. RESULTS: There were no differences between the genotypes in the visual contrast behavioral test, and there were no abnormal structures among the Dominant white chickens in the ophthalmic examination. The histological sections from the Dominant white chickens did not differ from the wild-type chicken in structure, photoreceptor density, or RPE pigmentation. CONCLUSIONS: The results indicate that the Dominant white mutation in PMEL17 does not seem to affect the visual ability or eye structures in chickens.

Magnetic resonance imaging findings in dogs with orbital inflammation.

OBJECTIVES: To describe MRI features of canine retrobulbar inflammation, their association with clinical findings and outcome and to assess the value of MRI in detecting orbital foreign bodies. MATERIALS AND METHODS: Clinical records of dogs with confirmed (23 of 31) and suspected (eight of 31) retrobulbar inflammation that underwent low field MRI studies were analysed retrospectively. RESULTS: Of the 31 dogs included in the study there was abscessation in 19. Extraocular myositis (27 of 31) was concurrent with strabismus in three cases. Of 25 patients with exophthalmos, 14 had concurrent optic nerve swelling and, of these, five had permanent loss of vision. There was no vision loss in patients without nerve swelling. One case of suspected retinal detachment on MRI was confirmed clinically. Extensive abnormal contrast enhancement in the temporalis, masseter and pterygoideus muscles was associated with facial (n=3) and trigeminal nerve deficits (n=1). Three patients with inflammation extending into the nasal cavity and frontal sinus (one of 31) or meningeal contrast enhancement (two of 31), showed optic and oculomotor nerve deficits. On MRI a foreign body was not visible in 20 of 31 case or "appeared likely" in 11 of 31 dogs. A foreign body was found at surgery in one case. CLINICAL SIGNIFICANCE: MRI outlines the extent of retrobulbar inflammation. Clinical findings were associated with imaging findings. MRI overestimated the presence of foreign bodies.