Posterior Uveitis, Chorioretinitis.
Posterior uveitis is inflammation of the choroid, the posterior part of the uveal tract. Inflammation of other components of the posterior part of the eye and inflammatory disorders of the pars plana
of the ciliary body are also included here. It may be focal, multifocal and diffuse in location. As the outer layers of retina depend upon the choroid for nutrition, there is always associated inflammation of retina (chorioretinitis). It occurs in two forms which is similar to anterior uveitis:
- Granulomatous choroiditis is due to direct pathogenic infection.
- Non-granulomatous choroiditis or exudative choroiditis is due to allergic reaction.
Clinical Types - Choroiditis is usually classified according to number and site of lesions:
- i. Disseminated (diffuse) - lesions are seen scattered all over the fundus, e.g. as in syphilis and tuberculosis.
- ii. Anterior - lesions are seen in the peripheral parts (near equator) of the fundus, e.g. as in syphilis.
- iii. Central - involves the macular area or posterior pole, e.g. as in toxoplasmosis, histoplasmosis.
- iv. Juxtapapillary (of Jensen) - lesions are present around the optic disc. It occurs in young persons.
Symptoms - ‘floaters’ (vitreous opacities consisting of debris and inflammatory cells), photopsia (flashing light) and decreased vision. Pain and redness are rare.
Signs - variable cells in the anterior chamber and vitreous, choroiditis (fluffy, raised lesions without pigment if active), retinitis (cotton wool spots, haemorrhages and cuffing, attenuation or dilatation of vessels), macular oedema and exudative retinal detachment. Specific inflammatory disorders that target the choroidal tissue are known as the white dot syndromes.
Investigations - distinguish whether the uveitis is infective or non-infective. Sixty percent of uveitis is idiopathic, with important underlying systemic disease in the remainder. Do baseline and specific tests: full blood count (FBC); urea and electrolytes (U&E); chest X-ray (CXR); angiotensin-converting enzyme (ACE); human leukocyte antigen tests (HLA-B27 and HLAA29); syphilis (Venereal Disease Research Laboratory (VDRL) test); enzyme-linked immunosorbent spot (ELISPOT) assay; lyme serology; antinuclear antibody (ANA) test and antineutrophil cytoplasmic antibodies (ANCA) test.
Treatment - Atropine (rest to the eye by paralysing the ciliary muscles), heat application by diathermy or an electric pad, corticosteroids, specific treatment is required for causative organism such as toxoplasmosis, toxocariasis, TB, syphilis, etc.