Feline uveitis. An 'intraocular lymphadenopathy'

Abstract

Practical relevance Feline uveitis can be a subtle, insidious, painful, vision-threatening disease with causes that can sometimes be fatal. It is essential that clinicians remain alert to its various clinical presentations, thoroughly diagnose cases once detected, and treat the primary cause whenever possible.

Clinical challenges In the majority of patients, a cause is not found and aggressive immunomodulating therapy of what may become a chronic or recurrent immune-mediated disease must be instigated. As with immune-mediated diseases elsewhere, this involves local or systemic immunosuppression with slow tapering and frequent monitoring. The aim of this review is to aid diagnosis and therapy of uveitis by likening it to inflammation elsewhere (because it is more similar than it is different) while highlighting differences (because these are helpful).

Global importance Feline uveitis is similar in its presentation throughout the world. Although the list of infectious causes may vary in composition or order of likelihood, idiopathic, immune-mediated and neoplastic causes of feline uveitis are universal.

Patient group Patients of either gender and all ages and breeds are affected by uveitis.

Evidence base Despite the fact that feline uveitis is a serious and common disorder, the peer-reviewed literature regarding this disease is somewhat limited. Approximately half the publications are review articles, case reports or case series. The majority of prospective and retrospective research describes epidemiologic surveys of antibodies, antigens and organism DNA in serum and aqueous humor.

Fig 1

The middle (uveal) tunic of the eye is located between the outer fibrous (corneoscleral) tunic and the inner neurosensory (retinal) tunic and is composed of the choroid posteriorly and the iris and ciliary body anteriorly

Fig 2

Oblique illumination is essential for examination of the anterior iris face. It is achieved by directing a bright and focal light source across the eye from the lateral canthus while viewing the eye from in front using a source of magnification

Fig 3 (a)

The normal anterior iris face is highly textured when viewed with oblique illumination and a source of magnification. (b) With uveitis, iridal swelling is evident as a ‘muddy’ or flattened iris surface, sometimes in association with nodular swellings. This eye also demonstrates rubeosis iridis (especially laterally) and keratic precipitates as grey spots against the inner cornea ventromedially

Fig 4

Deep episcleral vessels (arrowhead) should be differentiated from superficial conjunctival vessels (arrows). Where this is difficult, the aim must be to disprove that uveitis exists rather than assume that conjunctivitis exists. Note also the subtle corneal edema adjacent to the lateral limbus in this eye

Fig 5

A 12-year-old female spayed Manx cat with moderate hyphema and marked dense hypopyon bilaterally. This cat was diagnosed with lymphoma

Fig 7

Left eye of a 15-month-old female spayed domestic shorthair cat with a moderate-sized fibrinous clot in the ventromedial anterior chamber. A cause was not found for the uveitis

Fig 8

Aqueous flare can be detected by using the beam produced by the smallest circular aperture on a direct ophthalmoscope held as close as possible to the cornea in a completely darkened room and viewed transversely with magnification. Complete pupil dilation may allow aqueous flare to be seen more easily due to the apparent dark space created by the pupil

Fig 6

Right eye of a cat with marked, diffuse, unilateral hyphema as a result of recent blunt trauma

Fig 9

Keratic precipitates highlighted by retroillumination following pupil dilation

Fig 10

By conducting a thorough general physical and ophthalmic examination, as well as gathering a focused history, evidence can be assembled to strongly support or not the need for further diagnostic testing

Fig 11

White blood cell accumulation in the anterior vitreous is termed 'snow banking’ and may be seen with oblique examination of the eye following wide pupil dilation. This lesion is seen in patients with pars planitis or intermediate uveitis