Ocular disease is not common in the cat, occupying a surprisingly small proportion of the referral caseload. The eyelid tumours, conformational problems, cataracts and hereditary disease which are common in the dog are uncommon in the cat. As with anterior segment disease, however, the cat fundus shows conditions with interesting features.

Fortunately the normal feline fundus is easier for the clinician than the dog in having less intra-species variation. The great majority of cats have the 'textbook' appearance. The tapetal fundus is bright and extensive usually reaching ventral to the optic disc. The remainder of the fundus is dark brown. The optic disc is small, dark and circular and the main vessels leave the disc from the edge in three main groups without any anastomosis on the surface. In cats with a paler coat colour there is often a normal tapetum but complete lack of pigment ventrally exposing the extensive choroidal vasculature and the scleral beyond. In cats with very pale coats and/or blue irises there may be no tapetum and little pigment with choroidal vessel exposure over large areas.

This session will use a series of case studies to illustrate the range of conditions seen in the feline posterior segment and give some additional insights into each including pathogenesis. Conditions to be illustrated will include:

 Hypertension. This readily causes feline fundus changes and these, or usually blindness, may be the first sign noticed by owners. Although not a posterior segment sign, hyphaema is actually often the first change noted by owners and every effort should be made to examine beyond. The range of presentations and the pathogenesis will be illustrated.

 Feline coronavirus infection (FeCoV). All feline viruses may have posterior signs but the necrotising vasculitis of FeCoV appearing as grey sheathing of retinal vessels is pathognomic for that problem.

 Metastatic tumours. Carcinomas metastasising to the eye often form a striking pattern of carpet-like spread of cells over all internal ocular surfaces. This includes the inner retinal surface and the retinal choriocapillaris surface. Since they are often angioinvasive there may also be retinal infarction to complicate the picture. A fundus appearance has been described of normal or hyper-reflective tapetum alternating with non-pigmented swelling obscuring the tapetum in a zonal pattern. In many cases, however, other changes obscure fundus detail and the eye may be opaque.

 Optic disc swelling may be inflammatory or oedematous and is uncommon in the cat. Papilloedema results from raised intracranial pressure and may appear as simple swelling with a rather fluffy appearance or considerable enlargement with an excessively vascular appearance.

 Dental trauma. A dental instrument may penetrate the eye during extraction of the last molar tooth. The entry point is usually at the level of the peripheral retina with the instrument continuing to rupture the posterior lens capsule. If infection is introduced then a vitreous abscess may result.

 Sclerosing orbital pseudotumour describes tumour-like inflammatory tissue proliferation posterior to the globe. This is difficult to classify hence the rather unsatisfactory name of pseudotumour. In the case of the feline orbit the inflammation is actually overshadowed by accompanying fibrous proliferation which invades and binds the extraocular tissues. The lids become immobile and retracted, the eye also becomes fixed and exposure damage and poor cosmesis results. The less formal term of 'frozen orbit syndrome' is very apt.