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Describe keratic precipitates and the other signs of uveitis.

Ophthalmology · 3rd Professional

Keratic precipitates (KPs) are cellular deposits on the corneal endothelium, composed of inflammatory cells and fibrin that have settled out of the aqueous.
They are the hallmark of anterior uveitis, and their morphology and distribution indicate the type and duration of the inflammation.
Why they deposit where they do — a convection current flows in the anterior chamber, rising at the warmer iris and descending at the cooler cornea, carrying cells downward. They therefore settle in a triangular distribution over the inferior cornea with the apex upward — ARLT’S triangle. A different distribution is a diagnostic clue

Type of KP	Appearance and significance
Fine (small, white, punctate)	Non-granulomatous inflammation — HLA-B27 associated disease, trauma, idiopathic acute anterior uveitis
Mutton-fat (large, greasy, yellowish)	Granulomatous inflammation, composed of epithelioid and giant cells. Indicates tuberculosis, sarcoidosis, syphilis, VOGT-koyanagi-HARADA, sympathetic ophthalmitis or toxoplasmosis — and therefore demands investigation
Pigmented	Old, resolved KPs which have become pigmented; indicate past inflammation rather than present activity
Stellate (stellate, fine, with fibrillary extensions)	Distributed diffusely over the whole endothelium rather than in Arlt triangle — a distribution that is itself diagnostic. Seen in FUCHS heterochromic iridocyclitis, herpetic uveitis and Posner-Schlossman syndrome
"Endothelial dusting"	Very fine deposits in early or mild inflammation
Old, "ground-glass" or hyalinised	Long-standing chronic disease

Sign	Description and significance
Aqueous cells	Individual inflammatory cells seen as motile specks in the slit beam; indicate activity and guide treatment
Aqueous flare (tyndall effect)	A visible beam in the anterior chamber from protein leaking through a damaged blood-aqueous barrier — the same effect as a torch beam in a smoky room. It may persist after the inflammation has resolved and does not guide treatment
Hypopyon	Layered inflammatory cells in the lower angle. In uveitis it is sterile. A mobile, shifting hypopyon is characteristic of BEHCET disease; and a hypopyon with fibrin and marked flare of HLA-B27 associated disease
Iris nodules — KOEPPE	Small nodules at the pupillary margin; occur in both granulomatous and non-granulomatous disease
Iris nodules — busacca	Larger nodules on the anterior iris surface away from the margin; occur only in granulomatous disease
Nodules of BERLIN	In the angle, seen on gonioscopy
Posterior synechiae	Adhesions of iris to lens; produce an irregular, festooned pupil on dilatation, and if complete cause seclusio pupillae and iris bombe
Peripheral anterior synechiae	Adhesions of peripheral iris to the angle; cause chronic angle-closure glaucoma and are seen only on gonioscopy
Iris atrophy	Patchy or diffuse in Fuchs heterochromic iridocyclitis, causing heterochromia; and sectoral in herpes zoster.
Band keratopathy and complicated cataract	Signs of chronicity rather than of activity

Describe the KPs in the notes — their size, colour, number and distribution; they are the most informative single sign in anterior uveitis and are recorded merely as "KPs present"
Mutton-fat KPs mandate investigation; in India that means tuberculosis, sarcoidosis and syphilis first
Diffuse stellate KPs over the whole endothelium suggest Fuchs or herpetic disease — and in Fuchs, treatment with steroids is often unnecessary and harmful

All questions in Diseases of the Uveal Tract