Uveitis Classification (SUN) and a Workup You Can Reproduce Under Pressure

Uveitis classification is not a list to memorise in isolation. It is the language that turns a red-eye or blurred-vision stem into a reproducible description: where is the inflammation, when did it start, how long has it lasted, what is its course, how active is it, and what associated disease or masquerade must be considered? The Standardization of Uveitis Nomenclature (SUN) framework makes those descriptions comparable in notes, exams and studies.

This article is for postgraduate ophthalmology examination education. A real painful red eye, reduced vision, suspected infection or posterior-segment inflammation requires timely in-person ophthalmic assessment; this is not a remote diagnostic or treatment plan.

The direct answer: classify in six fields

When given an uveitis case, say the fields in this order:

1. Anatomical location: anterior, intermediate, posterior or panuveitis.
2. Laterality: unilateral, bilateral or alternating.
3. Onset: sudden or insidious.
4. Duration: limited or persistent.
5. Course: acute, recurrent or chronic.
6. Activity and phenotype: anterior-chamber cells/flare, vitreous activity, granulomatous/non-granulomatous features, retinal/choroidal lesions, vasculitis and systemic associations.

The uveitis study guide is the broader topic route. The present guide gives you the language and workup logic needed to avoid broad, low-yield “uveitis panels.”

Anatomical classification: use the primary site of inflammation

SUN uses the primary anatomical location—not simply every structure that has a cell or complication.

This is why an exam description should begin with “primary site” and then mention secondary involvement. An eye can have anterior-chamber cells with a posterior uveitic process; the classification follows where the principal inflammatory disease sits.

Time course: definitions that change the answer

SUN defines onset as sudden or insidious, duration as limited or persistent, and course as acute, recurrent or chronic. Those words are often tested because they impose discipline on a vague history.

An acute episode has a sudden onset and limited duration. A recurrent course involves repeated episodes separated by inactive periods without treatment for at least three months. Chronic uveitis persists and is characterised by prompt relapse—usually within three months—after stopping treatment. In an exam, phrase the interval explicitly instead of writing only “comes and goes.”

Do not assume that “chronic” equals “mild” or that “recurrent” defines an aetiology. They describe behaviour over time. A disease can be recurrent, unilateral and non-granulomatous; those are separate descriptors that together narrow the differential.

SUN anterior-chamber cells and flare: know the scale, then interpret it

SUN grades anterior-chamber cells using a 1 mm by 1 mm slit-beam field. The grading system gives a shared language, but it requires correct technique and should not be converted into a diagnosis by itself.

Flare is graded separately: 0 (none), 1+ (faint), 2+ (moderate with iris/lens details clear), 3+ (marked with hazy details) and 4+ (intense, often with fibrin). Cells represent inflammatory cells; flare reflects protein in aqueous and blood–aqueous barrier disruption. They are related but not interchangeable. A candidate who says “2+ cells and 2+ flare” has communicated two observations, not one severity score.

For research activity definitions, SUN 2005 described inactive anterior uveitis as rare cells or fewer, whereas improvement/worsening can be assessed in step changes. Subsequent SUN work has created disease-specific classification criteria; do not casually transplant a research definition from one entity into every clinical decision.

Vitreous activity: describe what you see

For intermediate and posterior disease, document vitreous cells and haze as well as retinal/choroidal findings. The Nussenblatt vitreous haze scale is commonly encountered in training. In a viva, it is sufficient to state that haze is a semiquantitative assessment of media clarity due to inflammation and that it should be interpreted with the view of the disc/fundus, imaging and the rest of the examination.

The important distinction is vitritis versus spillover. Mild vitreous cells can accompany marked anterior inflammation. Intermediate uveitis is not diagnosed from one stray vitreous cell; it requires that the vitreous is the primary site after considering the whole ocular picture.

Granulomatous is a clue, not a diagnosis

“Granulomatous” describes a clinical pattern, often including large greasy (“mutton-fat”) keratic precipitates, iris nodules or a chronic-appearing course. It can suggest conditions such as sarcoidosis, tuberculosis-related uveitis in an appropriate epidemiological setting, syphilis, Vogt–Koyanagi–Harada disease or other entities, but it does not prove any one of them. Conversely, a non-granulomatous pattern does not exclude significant systemic or infectious disease.

In a written answer, avoid the shortcut “granulomatous = sarcoid.” State: “This phenotype broadens the differential toward granulomatous and infectious/systemic causes; I would take a targeted history, examine for compatible signs, and select investigations that can change probability or management.”

The workup: phenotype first, tests second

The highest-value workup is a structured clinical description. A broad laboratory panel in every patient increases false positives and can distract from infection, masquerade or a time-critical posterior diagnosis. The workup below is a reasoning framework, not a substitute for local protocols or specialist assessment.

Step 1: identify urgency and masquerade risk

Ask about pain, photophobia, acute visual change, floaters, neurological symptoms, fever, rash, oral/genital ulcers, joint/back symptoms, respiratory symptoms, travel/exposures, immunosuppression, malignancy history and medicines. Examine both eyes: visual acuity, pressure, pupils, cornea, anterior chamber, iris, lens, vitreous, retina/choroid and optic nerve. Record the phenotype before ordering tests.

Urgent differentials can include infectious retinitis, endophthalmitis, acute retinal necrosis, severe bilateral posterior inflammation or a masquerade syndrome. The purpose of mentioning them in an exam is to show escalation awareness—not to diagnose remotely from one sign.

Step 2: make a phenotype statement

Use this complete sentence: “This is [unilateral/bilateral] [acute/recurrent/chronic] [granulomatous/non-granulomatous] [anterior/intermediate/posterior/panuveitis], with [key sign], and I would prioritise [two or three clinically plausible categories] while excluding [important infectious or masquerade concern].”

For example, a recurrent acute unilateral anterior pattern may lead you to ask about HLA-B27-associated disease and herpetic features, whereas bilateral granulomatous panuveitis needs a differently focused differential. The diagnosis comes from the total pattern, not from any single association.

Step 3: choose tests by pre-test probability

Tests should answer a question raised by the phenotype, history or examination. Syphilis serology is frequently considered because it is a treatable mimic with varied presentations; tuberculosis evaluation must be contextualised by exposure, endemicity, imaging and the broader clinical picture; sarcoid assessment is meaningful when the phenotype or systemic evidence supports it. HLA-B27 testing may be useful in an acute recurrent anterior phenotype, especially with suggestive systemic symptoms, but it is not an indiscriminate screening test.

Imaging is likewise targeted. OCT can define macular oedema or retinal architecture; fluorescein angiography can show vascular leakage or nonperfusion; fundus autofluorescence and indocyanine-green angiography can help in selected posterior/choroidal disorders; ultrasound is useful when media opacity prevents fundus view. State what the test is intended to reveal.

Step 4: re-evaluate after results

An abnormal test is not automatically causal. Recheck whether the result fits the ocular phenotype, the prior probability and the alternative diagnoses. This protects against anchoring on a positive result that is incidental or nonspecific.

Pattern recognition without overclaiming

The following table is a way to organise revision, not a list of diagnostic shortcuts.

“Pars planitis” is a SUN term for a subset of intermediate uveitis where there is no associated systemic disease or infection; it should not be used before those associations have been considered. This is a favourite distinction in examinations.

Complications and monitoring: keep anatomy in view

Uveitis affects more than inflammation grade. Record intraocular pressure, synechiae, cataract, corneal changes, macular oedema, optic nerve and retinal vascular status. Some are consequences of inflammation; some can relate to treatment; some reflect a different diagnosis. In a viva, say that monitoring follows the anatomical site and complication risk. For instance, OCT is particularly valuable when visual symptoms and macular involvement are possible, while pressure monitoring matters in recurrent anterior disease.

Avoid presenting corticosteroids, immunomodulation or antimicrobial therapy as a uniform response to “uveitis.” Infection must be considered before immunosuppression, and real treatment decisions belong with clinical examination, investigations and specialist/local guidance.

MCQ traps and a 40-second answer

Trap: “Panuveitis means severe anterior uveitis.” No: it means primary inflammation in anterior chamber, vitreous and retina/choroid.

Trap: “Cells and flare are the same.” No: cells are inflammatory cells; flare reflects protein/barrier breakdown, and each is graded separately.

Trap: “Intermediate uveitis equals pars planitis.” No: pars planitis is idiopathic intermediate uveitis after excluding association or infection.

Trap: “Order every autoimmune and infection test.” No: investigate the phenotype and exclude time-critical conditions.

The compressed answer is: “I would classify by anatomical site, laterality, onset, duration, course and activity. I would grade anterior chamber cells and flare separately, document vitreous and posterior findings, then form a phenotype-led differential. Investigations are targeted to the phenotype and should address infectious causes and masquerades where relevant; they are not a universal panel.”

For systematic question practice across adjacent topics, start with free ophthalmology MCQs; use real clinical supervision and current guidelines for patient care.

A note on classification criteria versus diagnosis

SUN terminology and later disease-specific classification criteria are designed to make research cohorts and clinical descriptions more consistent. Classification criteria generally prioritise specificity for study inclusion; they do not replace the clinician’s diagnostic reasoning in an individual. A patient may have an incomplete phenotype early in disease, more than one plausible association, or an alternative process that needs exclusion. In an exam, this distinction earns marks because it shows you understand why a checklist cannot replace history, examination and follow-up.

The same caution applies to imaging and laboratory results. OCT can demonstrate cystoid spaces but cannot by itself name the cause of inflammation. A positive immunological or infectious test has a meaning that depends on the pre-test probability and phenotype. A normal investigation does not automatically exclude a diagnosis when timing, test performance or prior treatment matters. Describe the evidence, then say how it shifts the differential.

For documentation practice, write one line at each visit: laterality; SUN anatomical class; onset/duration/course; cells and flare; vitreous/retinal activity; pressure; complications; and the leading differential with the reason for any test. This format makes subsequent change visible and prevents “uveitis, better” from becoming the whole clinical record.

For an oral examination, finish with safety: “If the phenotype suggests infection, severe posterior disease or a masquerade, I would prioritise urgent specialist assessment and avoid assuming that all inflammation has the same treatment.” It is concise, clinically mature and avoids a hazardous blanket prescription.

Sources

• Standardization of Uveitis Nomenclature (SUN) 2005 report, PubMed — original nomenclature, grading and course definitions.
• SUN Working Group disease-classification publications, PubMed search — current disease-specific research-classification literature, checked 18 August 2026.
• American Academy of Ophthalmology: Uveitis — professional education resource, accessed 18 August 2026.
• Uveitis, StatPearls — terminology and differential cross-check, accessed 18 August 2026.
• International Uveitis Study Group classification, PubMed — anatomical classification context.