Ocular biometry in rabbits using computed tomography.

OBJECTIVE: To describe a repeatable method of measuring ocular structures and to establish ocular biometry reference ranges in adult domestic rabbits (Oryctolagus cuniculus) without medical history or imaging findings consistent with ophthalmic disease using a 64-slice multidetector computed tomography scanner. PROCEDURE: In this retrospective and observational anatomic study, 100 eyes from 50 rabbits without medical history or imaging findings consistent with ophthalmic disease who received a head computed tomography scan were selected for measurement of globe length, width, and height using 3D multiplanar reconstruction. Lens width and length, the anteroposterior length of the anterior and vitreous chambers, and attenuation of the lens and vitreous chamber were collected. These parameters were compared against age, sex, weight, body condition, and ear conformation. RESULTS: A reference guide was established, with globe width being the largest dimension (18.03 ± 0.81 mm), followed by height (17.18 ± 0.69 mm) and then length (16.64 ± 0.66 mm). Increased weight was associated with an increase in globe height (p = 2.43 × 10-5 ), length (p = 1.63 × 10-4 ), and width (p = 7.0 × 10-3 ). Increased age was associated with increased lens attenuation (p = 1.28 × 10-7 ) and increased transverse lens width (p = 1.64 × 10-3 ). Inter- and intra-observer agreement was excellent. CONCLUSIONS: CT is a reliable modality for measurement of ocular biometry dimensions in rabbits. These reference values can be applied to aid in identifying diseases that affect the dimensions of the ocular structures in rabbits over 18 months of age.

Modelling Neurological Diseases in Large Animals: Criteria for Model Selection and Clinical Assessment.

Issue: The impact of neurological disorders is recognised globally, with one in six people affected in their lifetime and few treatments to slow or halt disease progression. This is due in part to the increasing ageing population, and is confounded by the high failure rate of translation from rodent-derived therapeutics to clinically effective human neurological interventions. Improved translation is demonstrated using higher order mammals with more complex/comparable neuroanatomy. These animals effectually span this translational disparity and increase confidence in factors including routes of administration/dosing and ability to scale, such that potential therapeutics will have successful outcomes when moving to patients. Coupled with advancements in genetic engineering to produce genetically tailored models, livestock are increasingly being used to bridge this translational gap. Approach: In order to aid in standardising characterisation of such models, we provide comprehensive neurological assessment protocols designed to inform on neuroanatomical dysfunction and/or lesion(s) for large animal species. We also describe the applicability of these exams in different large animals to help provide a better understanding of the practicalities of cross species neurological disease modelling. Recommendation: We would encourage the use of these assessments as a reference framework to help standardise neurological clinical scoring of large animal models.

Feline Uveal Melanoma Review: Our Current Understanding and Recent Research Advances.

Melanocytic neoplasia is the most common form of ocular tumour in cats, accounting for 67% of cases in an analysis of 2614 cases of primary ocular neoplasia. Feline diffuse iris melanoma (FDIM) is by far the most common form of ocular melanocytic neoplasia, with limbal melanomas and atypical melanoma (melanoma affecting the choroid or ciliary body) infrequently recognised. Early lesions begin as flat areas of pigmentation of the iris, known as iris melanosis. This melanosis is a precursor lesion that can become FDIM when pigmented cells infiltrate the anterior iris stroma, commonly alongside a transition in cell morphology. The differentiation between FDIM and benign iris melanosis is only recognisable though histologic examination, with no in vivo means of identifying the malignant transformation. The behaviour of FDIM is variable and difficult to predict. Some FDIM lesions have a more benign progression and can slowly grow or remain static for years without affecting the ocular or systemic health of the individual, whilst other tumours behave aggressively, invading the ocular structures and significantly affecting the life expectancy of cats through metastatic disease. This makes management and timely enucleation of these cases challenging in practice. This article aims to review our current knowledge of FDIM.

Ocular Tuberculosis: More than 'Of Mice and Men'.

Tuberculosis (TB), caused by infection with members of the Mycobacterium tuberculosis-complex, is one of the oldest known infectious disease entities, resulting in the death of millions of humans each year. It also results in a substantial degree of morbidity and mortality in animal species. Extrapulmonary TB is well recognized in humans, and the eye is one site that can be affected. Studies seeking to understand ocular TB have often relied on animal models; however, these have their limitations and may not truly reflect what happens in humans. We wish to raise awareness among ophthalmologists and vision scientists of naturally occurring cases of ocular TB in animals, namely cattle and domestic cats, and the possibilities of gaining further understanding of this presentation of TB by adopting a collaborative approach. This will hopefully improve outcomes for both human and animal patients.

Extraocular muscle dysinnervation disorder resembling Duane retraction syndrome in a 9-month-old French Bulldog.

A 9-month-old French Bulldog was presented with a chronic history of lateral strabismus and intermittent third eyelid protrusion in the left eye. The neuro-ophthalmological examination revealed mild ptosis of the left upper eyelid, mild lateral strabismus, and external ophthalmoparesis of the left eye. Retraction and ventral deviation of the left eye globe with protrusion of the third eyelid and elevation of the upper eyelid were elicited on attempted voluntary adduction of the left eye. Hematology, serum biochemistry, serology for infectious diseases, magnetic resonance of the head, and cerebrospinal fluid analysis did not reveal significant abnormalities. Forced duction test did not show signs of mechanical restriction in ocular motility. A suspected congenital cranial dysinnervation disorder resembling Duane retraction syndrome in humans was diagnosed based on the typical clinical signs and exclusion of structural abnormalities. The clinical signs remained stable for 9 months until the time of writing this report.

Uveal cysts in domestic cats: a retrospective evaluation of thirty-six cases.

OBJECTIVE: The aim of this retrospective study was to investigate uveal cysts in domestic cats by identifying prevalence, predispositions, location, presumed etiologies, and sequelae. ANIMALS STUDIED: The clinical databases of two referral hospitals (The Animal Health Trust in the UK and Animal Eye Care in Australia) were searched to identify cats that had been diagnosed with uveal cysts, either as an incidental finding or as the reason for referral. Thirty-six cases were found. PROCEDURES: The signalment of the patients was recorded, along with any relevant previous clinical history, treatment, follow-up, and sequela. The data were compared with the unaffected feline populations examined by ophthalmologists in the two hospitals over the same 10-year time period. RESULTS: Thirty-six cats were affected, from a total examined population of 5017 (prevalence 0.72%). Twenty-one of the 36 cats were Burmese. The two centers examined 516 Burmese cats in the same time period, giving an incidence in Burmese cats of 4.1%. The mean age of affected cats at presentation was 10.25 years (SD = 4.12 years), and female cats accounted for 23 of 36 of the cases. Only 2 of 36 cats had concurrent intraocular disease. CONCLUSIONS: Uveal cysts in domestic cats are rare ophthalmic findings, and in most cases, they do not cause any clinical problems The Burmese breed is overrepresented in the data, with a relatively high prevalence of uveal cysts.