The eye is red, but of especial importance is the presence of a pink flush around the cornea (the ciliary flush), which indicates an inflammatory process either in the cornea or within the anterior chamber of the eye itself. The pupil is small because the iris sphincter goes into spasm. Thus, the pupil of iritis is small and treatment is aimed at making it larger, whereas the pupil of acute glaucoma is large and treatment is aimed at making it smaller. Unless there is secondary glaucoma, the cornea remains bright and clear, but with a pen torch it might be pos sible to see that the aqueous looks turbid. That is to say, a beam of light shone through the aqueous resembles a beam of sunlight shining through a dusty room (Figure 18.1). Normally, of course, the aqueous is crystal clear even when examined with the slit-lamp biomicroscope.
The presence of an occasional cell in the aqueous can be normal, especially if the pupil has been dilated with mydriatic eye drops, but suspicion should be raised if more than three or four cells are seen. In fact, the early diagnosis of anterior uveitis can entail careful slit-lamp examination. It is usual to discriminate between the presence of cells in the aqueous and the presence of flare. The latter reflects a high protein content and is a feature of more longstanding disease. Because there are convection currents in the aqueous, inflammatory cells are swept down the centre of the posterior surface of the cornea and become adherent to it, often forming a triangular-shaped spread of deposits known as keratic precipitates, or "KP"s (Figure 18.2). The microscopic appearance of the KP is determined by the type of cells. If a granulo-matous type of inflammatory reaction is taking place, involving epithelioid cells and macrophages, the KP might be large, resembling oil droplets ("mutton fat KP"). This form of KP is seen in uveitis associated with sarcoidosis and also tuberculosis and leprosy. When the inflammation is nongranulomatous, a fine dusting of the posterior surface of the cornea could be evident. KPs tend to become absorbed
Figure 18.1. Flare.EO
but they can remain more permanently as pig-mented spots on the endothelium.
Anterior uveitis is often associated with the formation of adhesions between the posterior surface of the iris and the lens. These are called posterior synechiae and become evident when attempts are made to dilate the pupil because parts of the iris remain stuck to the pupil giving it an irregular appearance. In severe cases of anterior uveitis, pus can collect in the anterior chamber to the extent that a fluid level can be seen where the layer of pus has formed inferi-orly. This is known as hypopyon - literally, "pus below" (Figure 18.3). A hypopyon is an indication of severe disease in the eye and the patient
Figure 18.1. Flare.EO
Figure 18.3. Hypopyon. In addition, there are red blood cells and fibrinous exudate in the anterior chamber (with acknowledgement to Professor H. Dua).EQ
should preferably be treated in hospital as an inpatient. Hypopyon tends to occur in certain specific types of anterior uveitis. It is occasionally seen in elderly diabetics with inadequately treated corneal ulcers, particularly those with vascular occlusive disease. It is also seen in Beh$et's disease, which is a rare disorder characterised by hypopyon uveitis, and ulceration of the mouth and genitalia. A hypopyon is occasionally seen following cataract surgery and in such cases can be infective or noninfective in origin. It is fortunately a rare complication of modern cataract surgery and the use of intraocular acrylic lenses.
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