Ocular immunology and mechanisms of ocular inflammation

Prevalence of anterior uveitis in cases of systemic inflammatory response syndrome in dogs and cats

OBJECTIVE

To determine the prevalence of anterior uveitis in dogs and cats hospitalized with a diagnosis of systemic inflammatory response syndrome (SIRS).

ANIMALS STUDIED

Dogs and cats hospitalized between May 2020 and January 2021 were prospectively included.

PROCEDURES

Patients were categorized into two different groups: The first group included patients diagnosed with SIRS, and the second group included patients hospitalized without SIRS as a control group. Daily physical and ophthalmological examinations were conducted during hospitalization. Diagnosis of anterior uveitis was made based on the presence of aqueous flare, low intraocular pressure, and other associated ocular signs such as episcleral injection and miosis. A multinomial logistic regression analysis was conducted to investigate factors associated with SIRS and anterior uveitis development.

RESULTS

The study comprised 42 patients with SIRS and 26 patients without SIRS. Among those with SIRS, 38% developed anterior uveitis, whereas only 7.7% of patients without SIRS showed signs of anterior uveitis. The prevalence of uveitis was significantly higher in animals with SIRS compared to those without SIRS (p < .05).

CONCLUSION

Anterior uveitis is more prevalent in patients with SIRS than patients without SIRS. Therefore, complete ophthalmic examination is recommended in all patients presenting with this syndrome.

Immunohistochemical findings in eyes of cats serologically positive for feline immunodeficiency virus (FIV)

In this study the eyes of 15 cats in the terminal stage of FIV infection were examined. The findings were compared to those in cats, which were euthanized because of other infectious diseases for for non-infectious reasons. Thirteen FIV-infected cats showed an anterior uveitis by means of light microscopy. No accumulation of retinal lesions were found in FIV-infected cats compared to the other cats examined. Additionally, there were no indications of lesions caused by opportunistic infections. In the posterior segments of the eyes, immunohistochemical examinations proved the plasma proteins C3 and IgG to be predominantly intravascular. The eyes of 11 serologically FIV-positive cats were available for immunohistochemical examination. In all 11 cats at least one of the plasma proteins C3 or IgG could be detected in the extravascular tissue of the anterior uvea. The extravascular presence of plasma proteins within the tissue seemed to be caused by an increased permeability of the vessels due to inflammation. Furthermore, the similar extravascular distribution pattern of IgG and complement component C3 in four cases indicated that immune complexes may play a role in the anterior uveitis of FIV-infected cats.

Microbiology of the canine and feline eye

Knowledge of the microbiology of the canine and feline eye in normal and pathologic states is an important aspect of the clinician's assessment of external ocular disease. Gram-positive bacteria predominate in surveys of microbial flora in normal and diseased eyes. These same organisms are routinely isolated from skin and the upper respiratory tract. Injury to the eye may result in proliferation and potential pathogenicity of normal ocular flora. A variety of bacterial, fungal, viral, and other microbial isolates affect the diagnosis and treatment of external ocular disease.

Immunologically mediated ocular disease in the horse

The continued study of immunology and its relationship to diseases of the eye will hopefully give some insight into the pathogenic mechanisms of certain ocular diseases of many species, including the horse. It may lead to a better understanding of equine recurrent uveitis, a disease that has remained an enigma for years and that now appears to be an immunologic hypersensitivity response to a number of varied antigens. The precise mechanism of the inflammation is still unclear, and the immunologic response may be variable or mixed depending upon the inciting antigen. Other ophthalmic diseases in the horse, such as conjunctivitis, chorioretinitis, and less well-defined entities such as superficial punctate keratitis, may also have an immunologic component in their pathogenesis. An appreciation of immunopathologic mechanisms may thus enhance the veterinarian's understanding of the pathophysiology and treatment of equine ocular disease.