Arlt's triangle describes which pattern on the cornea?

Mutton-fat keratic precipitates in an inverted triangle inferiorly Arlt's triangle is a distribution of mutton-fat keratic precipitates forming an inverted triangle over the central to inferior corneal endothelium.

A vortex whorl of epithelial deposits

A horizontal band of calcium at the interpalpebral zone

A ring infiltrate at the corneal periphery

Which cells make up the greasy precipitates of Arlt's triangle?

Macrophages and epithelioid cells The white-yellowish greasy deposits are clumps of inflammatory cells, specifically macrophages and epithelioid cells.

Why do the keratic precipitates of Arlt's triangle collect inferiorly?

Gravity and anterior chamber convection currents Gravity and convection currents within the anterior chamber, together with the cooler inferior cornea, deposit the precipitates in a triangular wedge below.

Blinking sweeps them downwards mechanically

The inferior endothelium has more pump sites

Tear film osmolarity is highest inferiorly

Arlt's triangle is a clinical sign of which type of intraocular inflammation?

Granulomatous inflammation in the anterior chamber The pattern is characteristic of granulomatous inflammation of the anterior chamber and is found in several types of anterior uveitis.

Non-granulomatous anterior uveitis

Sterile allergic conjunctival inflammation

Which trio of diseases heads the differential diagnosis for Arlt's triangle?

Sarcoidosis, syphilis and tuberculosis Mutton-fat precipitates in Arlt's distribution suggest a chronic granulomatous process, with sarcoidosis, syphilis and tuberculosis leading the differential.

Keratoconus, dry eye and blepharitis

Glaucoma, cataract and pterygium

Retinitis pigmentosa, Stargardt and Best disease

How is Arlt's triangle typically diagnosed in clinic?

Slit-lamp biomicroscopy with diffuse or focal illumination The inverted triangle of precipitates is visualised at the slit lamp using diffuse illumination, direct focal illumination or an optic section.

Fluorescein angiography of the anterior segment

Ultrasound biomicroscopy of the ciliary body

Corneal topography with elevation maps

How specific is Arlt's triangle for the cause of a patient's uveitis?

It is suggestive but not pathognomonic of any aetiology Arlt's distribution is a general finding suggestive of granulomatous inflammation, but it does not point to any specific uveitis aetiology.

It is diagnostic of ocular sarcoidosis

It confirms an infectious rather than autoimmune cause

It reliably distinguishes syphilis from tuberculosis

What happens to the large granulomatous keratic precipitates as inflammation is controlled?

They pigment and shrink, often leaving an endothelial halo With resolution or steroid therapy the precipitates pigment and shrink, but often fail to disappear entirely and may leave a halo on the endothelium.

They enlarge and vascularise into a corneal pannus

They migrate into the corneal stroma as scars

They calcify into a dense band keratopathy

What is the mainstay of treatment for the uveitis producing Arlt's triangle?

Topical corticosteroids used aggressively at first Topical corticosteroids are the mainstay and should be used aggressively during the initial phase, with a cycloplegic added to ease pain and prevent synechiae.

When should depot corticosteroid injections be avoided in uveitis with Arlt's triangle?

When an infectious cause is suspected Depot steroids should be avoided when uveitis may be infectious, because of their potentially severe adverse effects in that setting.

In every patient older than sixty

Whenever cystoid macular oedema is present

In any patient already on a cycloplegic

Arlt's Triangle: causes, examination and management

Disease Entity

Arlt’s triangle is a distribution pattern of mutton-fat keratic precipitates, which deposit as an inverted triangle on the central to the inferior cornea, forming a wedge-shaped region on the inferior corneal endothelium.

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The white-yellowish-greasy precipitates of inflammatory cells (macrophages and epithelioid cells) are clumped in a triangular fashion in the lower part of the anterior chamber due to gravity and convection current.

It is a clinical sign characteristic of granulomatous inflammation in the anterior chamber and is commonly found in several types of anterior uveitis. Arlt’s triangle distribution is a general finding and not suggestive of any specific uveitis etiology.

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History

Arlt’s triangle is named after Carl Ferdinand Ritter von Arlt’s (1812-1887), an Austrian ophthalmologist who was also the first physician to prove that myopia is a consequence of excessive axial length of the eye.

Etiology of Arlt’s Triangle

Arlt’s distribution pattern of mutton fat keratic precipitates is suggestive of a chronic granulomatous inflammatory process. The differential diagnosis includes anterior uveitis associated with sarcoidosis, syphilis, and tuberculosis.

Clusters of large, fluffy, lardaceous KPs with greasy appearance forming Arlt’s triangle may also occur in other unusual chronic infections e.g. leprosy, brucellosis, coccidiomycosis.

Pathophysiology of Arlt’s Triangle

Arlt’s distribution is caused by convection currents within the anterior chamber and the cooler temperature in the inferior cornea.

The larger granulomatous KPs will pigment and then shrink as inflammation abates or is controlled by steroid therapy.

They often fail to disappear completely, and they may alter the endothelium where they rest, leaving a halo on the endothelium.

Diagnosis of Arlt’s Triangle

Clinical Diagnosis

Arlt’s triangle is typically diagnosed during slit-lamp biomicroscopy. The keratic precipitates forming an inverted triangle on the inferior corneal epithelium can be visualized during slit-lamp examination in diffuse illumination, as well as direct focal illumination or an optic section.

in some cases, this collection of sticky inflammatory cells on the central and inferior cornea is so large in size, that it’s visible with the naked eye.

Differential Diagnosis

Arlt’s triangle is suggestive, but not pathognomonic, of granulomatous inflammation. Differential diagnosis should also include unusual chronic inflammatory conditions including :

Sarcoidosis
Syphilis
Tuberculosis
Vogt-Koyanagi-Harada disease
Sympathetic ophthalmia
Lens-induced uveitis
Brucellosis
Lyme disease
Leprosy
Presumed ocular histoplasmosis syndrome (POHS)
toxocariasis
Toccidiomycosis

Diagnostic Work-Up

Venereal Disease Research Laboratory (VDRL) test, FTA-ABS (or similar treponemal specific serology) test for syphilis A specific antitreponemal test must be obtained, as RPR or VDRL can provide false-negative results on RPR or VDRL.

CBC with differential

Angiotensin-converting enzyme (ACE) test for sarcoidosis may be obtained but is not very sensitive or specific, especially in children.

Anergy evaluation for sarcoidosis (rarely done)

Lyme serology if Lyme disease is suspected (eg, endemic area, tick bite, systemic manifestations)

Toxoplasmosis enzyme-linked immunosorbent assay (ELISA) if posterior uveitis associated

Antineutrophil cytoplasmic autoantibodies: c-ANCA with PR3 specificity is most specific for Wegener granulomatosis. c-ANCA is found in 80-95% of active cases. Isolated anterior uveitis (without orbital, scleral, or corneal involvement) is a very rare presentation of Wegener granulomatosis.

Cytology, polymerase chain reaction, and cultures of intra-ocular fluid when infection or masquerade suspected
In cases of suspected Acute Retinal Necrosis, anterior chamber fluid and/or vitreous should be examined via polymerase chain reaction (PCR) for HSV and herpes zoster virus nucleic acid.

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Management of Arlt’s Triangle

General treatment

Cycloplegia: Use a long-acting cycloplegic agent, such as cyclopentolate or homatropine, to relieve both pain and photophobia (if present) and to prevent the formation of posterior synechiae. However this may not always be necessary for chronic disease, especially if the inflammation is well controlled. In any case, allowing for some pupil movement is helpful to prevent posterior synechiae formation in the dilated position.

Corticosteroids :

Topical corticosteroids are the mainstay of therapy and should be used aggressively during the initial phases of therapy.
Subconjunctival injection of shorter-acting or depot steroids may be used if the patient poorly complies with topical therapy or if the inflammation is not responding to topical corticosteroids.
Betamethasone (Celestone) is short and intermediate-acting and can be used for exacerbations, whereas triamcinolone acetate is longer acting and is used more often for associated cystoid macular edema or vitritis. Depot steroids should be avoided in cases of uveitis secondary to any suspected infectious process because of their potentially severe adverse effects.
Oral steroids in severe cases may be added to the treatment regimen (after ruling out the infectious etiology or after under coverage of the medication, which treats the infectious etiology).

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Test yourself

A few questions straight from this article.

1 / 10 0 correct

Arlt's triangle describes which pattern on the cornea?
Arlt's triangle is a distribution of mutton-fat keratic precipitates forming an inverted triangle over the central to inferior corneal endothelium.
Which cells make up the greasy precipitates of Arlt's triangle?
The white-yellowish greasy deposits are clumps of inflammatory cells, specifically macrophages and epithelioid cells.
Why do the keratic precipitates of Arlt's triangle collect inferiorly?
Gravity and convection currents within the anterior chamber, together with the cooler inferior cornea, deposit the precipitates in a triangular wedge below.
Arlt's triangle is a clinical sign of which type of intraocular inflammation?
The pattern is characteristic of granulomatous inflammation of the anterior chamber and is found in several types of anterior uveitis.
Which trio of diseases heads the differential diagnosis for Arlt's triangle?
Mutton-fat precipitates in Arlt's distribution suggest a chronic granulomatous process, with sarcoidosis, syphilis and tuberculosis leading the differential.
How is Arlt's triangle typically diagnosed in clinic?
The inverted triangle of precipitates is visualised at the slit lamp using diffuse illumination, direct focal illumination or an optic section.
How specific is Arlt's triangle for the cause of a patient's uveitis?
Arlt's distribution is a general finding suggestive of granulomatous inflammation, but it does not point to any specific uveitis aetiology.
What happens to the large granulomatous keratic precipitates as inflammation is controlled?
With resolution or steroid therapy the precipitates pigment and shrink, but often fail to disappear entirely and may leave a halo on the endothelium.
What is the mainstay of treatment for the uveitis producing Arlt's triangle?
Topical corticosteroids are the mainstay and should be used aggressively during the initial phase, with a cycloplegic added to ease pain and prevent synechiae.
When should depot corticosteroid injections be avoided in uveitis with Arlt's triangle?
Depot steroids should be avoided when uveitis may be infectious, because of their potentially severe adverse effects in that setting.

Arlt’s Triangle: causes, examination and management