Classification of uveitis
Updated: Dec 27, 2022
Uveitis is defined as inflammation of the uveal tract (the iris, ciliary body and choroid), and in some cases the surrounding structures (retina, vitreous or anterior chamber). In this article, we describe the classification of uveitis by it’s anatomical location.
As the uveal tract is made up of the iris, ciliary body, and choroid, we’ll first dive in to the anatomy of the region. Check out our anatomy section for the detailed anatomy!
The iris is the most anterior part of the uvea, consisting of two parts, the 1) stroma, and 2) posterior pigmented layer.
The ciliary body consists of 1) the stroma, 2) muscle, and 3) epithelium. It is divided into two parts, the pars plicata anteriorly and the pars plana which lies more posteriorly.
the pars plana: an avascular flat (plana = flat) portion between the ora serrata and ciliary processes of the pars plicata.
the pars plicata: a highly vascularised folded layer which forms an attachment for lens zonules
💡 As it is avascular, the pars plana is a good site for intravitreal injections or vitreous removal (you may have heard of pars plana vitrectomy)
The choroid is the layer which lies between the sclera and the retinal pigment epithelium. It provides nutrients to the outer layers of the retina, and is perfused via two long posterior ciliary arteries, (short posterior ciliary artery and anterior ciliary artery) It is made of two layers:
Bruch’s membrane: this is the innermost layer, it’s function is unclear however it may play a part in fluid transport from the choroid to the retina, and is also permeable to fluoroscein
Vascular layer: this is split up into the choriocapillary layer, a medium vessel layer, and a large vessel layer
The Standardisation of Uveitis Nomenclature (SUN) Working Group guidance on uveitis terminology, endorsed by the International Uveitis Study Group (IUSG), categorises uveitis anatomically:
Iris +/- pars plicata
Iritis, Iridocyclitis Anterior cyclitis
Pars plana and vitreous
Pars planitis, hyalitis Posterior cyclitis
Choroid and retina
Chorioretinitis, retinitis, neuroretinitis
All of the above
Anterior uveitis refers to inflammation of the iris and pars plicata (the anterior part of the ciliary body). The commonest presentation you will have come across is acute anterior uveitis, particularly associated with HLA-B27 associated conditions.
The hallmark features are pain, redness, photophobia
Anterior chamber cells
Aqueous flare (with inflammation, proteins seep out of leaky blood vessels into the anterior chamber fluid)
Iris nodules (Busacca and Koeppe nodules)
Posterior synechiae (adhesions where the iris adheres to the anterior lens capsule, resulting in an irregular pupil which is sluggish in it’s reaction to light)
Complications such as cystoid macular oedema, band keratopathy and secondary glaucoma
Acute and chronic
It can be of acute or chronic (>3 months) onset, however the commonest presentation of anterior uveitis is acute anterior uveitis - AAU. AAU typically has a sudden onset and a limited duration, with symptoms that usually quickly resolve with anti-inflammatory therapy. For the uveitis to be of a limited duration, inflammation must not recur for at least 3 months following tapering of steroids. In chronic disease however, inflammation typically will recur as soon as anti-inflammatory therapy is stopped.
Granulomatous and non granulomatous
Anterior uveitis can also be divided into granulomatous (due to underlying granuloma-forming disease), and non-granulomatous causes.
Usually a chronic form of uveitis and is due to granuloma-forming underlying disease
Examples include sarcoidosis, tuberculosis, syphilis
Specific features include ‘mutton fat’ keratic precipitates
Busacca nodules (only seen in granulomatous) and Koeppe nodules (also seen in non-granulomatous). These are inflammatory cell precipitates, Busacca nodules lie on the iris surface whilst Koeppe nodules lie on the pupillary margin
Fine ‘Stellate’ keratic precipitates
Koeppe nodules only
Causes split up by aetiology:
TB, Lyme disease, syphilis, varicella zoster
Acute management: steroid drops (e.g. prednisolone acetate 1%) and cyclopentolate
The basic workup for acute anterior uveitis includes HLA-B27 and syphilis testing. For bilateral granulomatous disease one should also consider testing for sarcoid (CXR at least).
Intermediate uveitis is inflammation of the posterior ciliary body (pars plana) and vitreous. This is a rarer form of uveitis. It is rarer than other forms, and is typically painless with no red eye. It’s onset is also usually insidious and bilateral.
Slow onset, bilateral
Painless, no red eye
Snowballs: white focal inflammatory cells and exudates
Snowbanking: white exudates on the ora serrata which may extend onto the pars plana
Peripheral periphlebitis: strong association with multiple sclerosis!
Causes split up by aetiology:
Sarcoidosis, MS, inflammatory bowel disease
Lyme disease, Toxocariasis, Whipple’s disease, Syphilis, Leprosy
CMO - much more common in intermediate uveitis, complicating up to 50% of cases
Optic disc swelling
Band keratopathy (complicating up to 40% of cases!)
Posterior uveitis is inflammation of the choroid +/- retina. It is the rarest form of uveitis, and the most likely to result in vision loss. Whilst some cases may be asymptomatic, others may have a sudden onset with acute deterioration.
Reduced visual acuity
Blurred or lost vision
Difficulty seeing in the dark
Difficulty seeing colour
💡 While anterior uveitis often causes a painful red eye, light sensitivity and blurred vision, the symptoms of posterior uveitis are more subtle. As we go further back in the eye from anterior to posterior, inflammation is more likely to result in visual loss as the retina/choroid is affected.
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