Uveitis is the cause of 5-20% of legal blindness in developed countries.1 Diagnosis and treatment of uveitis depend on the degree of reported visual impairment and the quantification of inflammation within the eye. This quantification and subsequent grading are especially useful in tracking visit-to-visit improvement and the efficacy of a pharmacologic intervention.
This article will discuss the basics of the Standardization of Uveitis Nomenclature (SUN) Working Group uveitis terminology, anterior chamber inflammation grading, and vitreous inflammation grading. The cheat sheet below presents several tables that cover the grading schemas discussed below.
Before any discussion of grading schema, an understanding of common uveitis terminology is necessary. Cell, flare, and haze are standard descriptive terms. Cell refers to the number of inflammatory cells seen in a specific eye chamber. Flare is a term distinct to the anterior chamber that refers to the fog-like effect caused by protein exudation from vascular leakage in inflammation. Haze is a term specific to the vitreous cavity that refers to the haze caused by protein exudation and inflammatory cells in the vitreous humor.
Standardization of uveitis descriptors is essential for the diagnosis and monitoring of inflammation. The 2005 Standardization of Uveitis Nomenclature (SUN) Working Group Report was a seminal publication that reported a consensus for several necessary uveitis grading schemas and descriptors of disease2.
Anterior uveitis is inflammation in the eye's anterior chamber (AC). The AC is bounded by the corneal endothelium and the anterior surface of the iris. Common causes of anterior uveitis include systemic HLA-B27-related disorders to infectious etiologies such as herpes simplex.
Intermediate uveitis is defined by inflammation in the vitreous humor, the gel-like fluid between the lens and the retina. Although over 70% of intermediate uveitis is idiopathic, common identifiable causes range from infectious etiologies, such as tuberculosis, to non-infectious etiologies, such as lymphoma or multiple sclerosis. Intermediate uveitis may present with vitreous exudates accumulating over the pars plana and inferior peripheral retina; these exudates are called snowbanks.
Snowballs, on the other hand, are clusters of inflammatory cells and exudate in the inferior vitreous. Intermediate uveitis is present with snowbanking or snowball formation, and the idiopathic most common variant is pars planitis.
Posterior uveitis is defined as inflammation of the retina or choroid. This term encompasses both choroiditis, inflammation of deeper blood vessels, and retinitis, inflammation of the retina. Causes include infectious causes, such as toxoplasmosis and syphilis as well as non-infectious etiologies, such as punctate inner choroidopathy or birdshot chorioretinopathy.
Panuveitis is defined as inflammation found within all chambers with no predominance in any specific location. Panuveitis is often associated with systemic diseases such as sarcoidosis, syphilis, tuberculosis, or Vogt-Koyanagi-Harada disease.
Uveitis can present as a combination of chronic inflammation and acute flares of inflammation. Thus, an accurate description of the onset, duration, and course of disease presentation is vital. In addition to the anatomical descriptors defined above, the SUN Working Group also defined descriptors for onset, duration, and course (Table 1-Cheat Sheet).
Onset can either be described as insidious or sudden. Duration is limited if the uveitis episode lasts less than 3 months and persistent if the episode lasts more than 3 months.
The combination of onset, duration, and recurrence defines the disease course.
- Acute course is one with sudden onset and limited duration.
- Chronic course is a persistent duration with recurrence within 3 months of treatment discontinuation.
- Recurrent course is characterized by repeated uveitis episodes separated by periods of inactivity greater than three months since treatment discontinuation.
Anterior chamber grading
As previously mentioned, common findings of AC inflammation are cell and flare. The SUN Working Group defined their two AC grading schemas around these two findings. Importantly, for all grading schemas discussed in this article, an improvement in inflammation is a two-step decrease in grade. A worsening of inflammation occurs with a two-step increase in grade.
Exceptions include an improvement in 0.5+ grading and a worsening of 3+ grading. For both, a one-step change would suffice.
The AC cell grading schema is an ordinal scale of 0 to 4+ increasing with the number of cells. The findings are standardized under a slit lamp beam of 1 mm x 1 mm at the highest illumination.
AC cell grading schema
- 0 cells in the field are graded as 0.
- 1 to 5 cells are graded as 0.5+, often called trace inflammation.
- 6 to 15 cells in the field are graded as 1+.
- 16 to 25 cells on the field are graded as 2+.
- 26 to 50 cells on the field are graded as 3+
- Greater than 50 cells on the field are 4+
Note that a hypopyon is not included in SUN grading and should be described separately.
Grading anterior chamber flare follows a similar ordinal scale of 0 to 4+ with increasing flare. Whereas individual cells are counted for AC cell grading, here, a qualitative description of clarity of the iris and lens is used as the main metric.
Anterior Chamber Flare Grading
- Grade of 0 is defined as no haze seen.
- 1+ grade presents with faint haze, and 2+ presents with moderate haze.
- Grade of 3+ is defined as marked inflammation with hazy visualization of the iris and lens.
- Grade of 4+ has intense haze with fibrin or plastic aqueous seen at the slit lamp.
Similar to AC grading, vitreous inflammation is graded on cells and haze in the vitreous humor. Uniquely, vitreous haze can present as a sign of intermediate uveitis and posterior or panuveitis. It often deteriorates vision far more significantly than anterior chamber inflammation.3
The Multicenter Uveitis Steroid Treatment (MUST) Trial provided a vitreous cell grading scale.4 In a slit lamp field of 1 mm x 0. 5mm, the cells were graded on an ordinal scale of 0 to 4+.
Vitreous Cell Grading Scale
- A grade of 0 presents with no cells.
- 1 to 5 cells were seen in the field are graded as 0.5+.
- 6 to 10 cells are graded as 1+
- 11 through 20 cells are graded as 2+.
- 21 through 50 cells are given a grade of 3+
- 4+ is graded as fifty-one or more cells
Vitreous haze is analogous to the discussion of AC flare above. Similar to the SUN AC flare grading schema, the National Institute of Health (NIH) Scale, first presented by Nussenblatt in 19855, grades vitreous haze based on visualization of anatomic landmarks compared to a set of standardized fundus photos (Table 5-Cheat Sheet). In this case, it is the posterior pole.
Like the other grading schemas discussed, it is an ordinal scale with grading from 0 to 4+.
NIH Vitreous Haze Grading Scale
- Normal findings of no haze are graded as 0.
- A grade of 0.5+ or trace haze is defined as slight blurring of the optic disc margin.
- Obscured view with definition to the optic nerve head and retinal vessels is given a grade of 1+. Obscured view with definition to the retinal vessels is grade 2+ vitreous haze.
- A grade of 3+ is given for the case where the optic nerve head is visualized, but with blurry borders.
- An obscured fundal view is defined as a grade 4+.
SUN Machine Learning Criteria
In 2021, the SUN working group published machine-learning derived classification criteria for the 25 most common uveitides. These include uveitis that presents as anterior uveitis, intermediate uveitis, posterior uveitis, and panuveitis. The overall classification criteria for each category were greater than or equal to 94%. Individual criteria for each type of uveitis are published but beyond the scope of this article to delve into the classification criteria for each.
It is important to note that these criteria were created for research purposes, prioritizing specificity, rather than for diagnostic purposes, prioritizing sensitivity. However, they still guide describing the salient features of each of these diseases.
- Muñoz-Fernández S, Martín-Mola E. Uveitis. Best Practice & Research Clinical Rheumatology 2006;20:487–505. Available at: [Accessed May 16, 2022].
- Jabs DA, Nussenblatt RB, Rosenbaum JT, et al. Standardization of Uveitis Nomenclature for Reporting Clinical Data. Results of the First International Workshop. American Journal of Ophthalmology 2005;140:509–516. Available at: [Accessed May 16, 2022].
- Davis JL, Madow B, Cornett J, et al. Scale for Photographic Grading of Vitreous Haze in Uveitis. Am J Ophthalmol 2010;150:637. Available at: /pmc/articles/PMC3220938/ [Accessed June 4, 2022].
- Group TMUSTTR. The Multicenter Uveitis Steroid Treatment (MUST) Trial: Rationale, Design and Baseline Characteristics. Am J Ophthalmol 2010;149:550. Available at: /pmc/articles/PMC2975449/ [Accessed June 4, 2022].
- Nussenblatt RB, Palestine AG, Chan CC, Roberge F. Standardizatlon of Vitreal inflammatory Activity in Intermediate and Posterior Uveitis. Ophthalmology 1985;92:467–471. Available at: [Accessed June 4, 2022].