PG Series: Classification & Clinical Features of Uveitis

Classification of Uveitis:

A. Pathological or Woods Classification:

• Woods classification is also known as pathological or clinicopathological classification
• Uveitis is classified as granulomatous or nongranulomatous on the basis of the predominant clinical characteristics.

B. IUSG classification:

• International Uveitis Study Group (IUSG) classification of uveitis was originally devised by the International Uveitis Study Group in 1987.
• This classification is largely based on the anatomic position of the inflammation within the eye

C. SUN Classification:

• Most recent and widely accepted version of classifying uveitis is the Standardization of Uveitis Nomenclature (SUN) Classification.
• According to SUN classification, uveitis was divided according to their primary site of inflammation

Descriptors of Uveitis:

Clinical features of uveitis:

Common symptoms of uveitis:

Signs

Keratic Precipitates (KPs):  

KPs are cellular deposition on corneal endothelium during uveitis.

Pathogenesis of KP:  Migration of inflammatory Cells across the iris and ciliary vessels to aqueous humour ® In AC, these cells come across a convection current (due to temperature difference between inflamed warm iris & relatively cooler cornea) ® They start moving AC ®Because of the altered nutrition (inflammatory products in aqueous), corneal endothelium becomes sticky and may desquamate in places. And circulatory cells due to centrifugal convection current (convection currents in the anterior chamber that rise along the warm iris and fall along the cool cornea) and gravity often sticks on the corneal endothelium, which are termed as Keratic precipitates (KP).

Cells

• Cells in the aqueous is usually seen when there is inflammation of iris and ciliary body.
• Cells in the anterior chamber are counted using slit-lamp with a beam of 1 x 1 mm slit and graded according the SUN classification

Flare:   Aqueous humor is considered optically empty and if a slit- lamp beam is passed through it, the beam cannot be seen.  In case of inflammation, when breakdown of the blood-aqueous barrier occurs, there is increased protein content in the aqueous and if slit beam is obliquely aimed across the anterior chamber, the path of the beam can be seen, which is termed flare.

Flare is graded according to the scheme proposed by SUN classification

Iris nodules:   

• Iris nodules are very important signs of systemic disease. Iris nodules can be seen in both inflammatory & no-inflammatory conditions.
• Koeppe & Busacca nodules are pathognomic of granulomatous uveitis.

Examination of vitreous:

• Cells in the anterior vitreous or retrolental space should be looked for after pupillary dilation. Though there is no standard grading system for vitreous cells, documentation of this finding is important for follow-up of a uveitic case.
• Vitreous should be carefully examined with a 78/90D and also with indirect ophthalmoscope with indentation for snow ball opacities, snow-banking in pars plana region and vitreous strands
• For classifying vitreous haze, SUN classification has adopted The National Eye Institute system for grading vitreous haze with the proviso that the designation “trace” be recorded as 0.5+.

Examination of Fundus:

• Optic disc should be carefully examined with the help of slit lamp biomicroscopy. Disc hyperaemia, disc oedema, or optic neuritis is seen in various uveitic conditions.  Glaucomatous damage to the optic disc due to Secondary glaucoma, Neovascularization of the optic disc, optic disc granuloma and optic atrophy may also occur in uveitic patients.
• Examination of retinal vasculature for vasculitis, vascular sheathing, and accumulation of inflammatory cells around vessels is important. Vascular sheathing is seen as white parallel lines along vessels.  Sometimes inflammatory exudates are seen around the vessels in patients with sarcoidosis, known as candle-wax drippings. Also it is important to determine whether retinal veins, retinal arteries, or both are affected as it can help in differential diagnosis of the uveitic entity.

• Careful examination of the posterior segment can reveal inflammatory patches in the fundus. It is important to distinguish such lesions whether it involves retina or choroid or both. Sometimes these lesions are associated with subretinal fluid or localized haze in vitreous.

• Often    a patient can present with a retinal detachment. Exudative retinal detachments can be seen in a number of ocular inflammatory diseases like Vogt–Koyanagi–Harada syndrome. One should be able to distinguish rhegmatogenous retinal detachment from such cases, which requires a surgical management. Sequlae to vasculitis can lead to development of traction retinal detachment and should be dealt properly.
• Meticulous examination of the fovea with slit lamp biomicroscopy often helps to identify cystoid macular oedema, choroidal neovascular membrane or sight threatening inflammatory lesions like serpiginous choroiditis.  Cystoid macular oedema is a common in patients with uveitis which if long standing can lead to formation of macular hole.