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PubMed This is a summary of 18 peer-reviewed journal articles Updated
Ophthalmology

Understanding Your Tests and Results

At a Glance

Doctors diagnose uveitis using slit-lamp exams to grade inflammation (cells and flare), advanced imaging like OCT to check for retinal swelling, and blood tests to find underlying systemic causes. If all blood tests are negative, the condition is called idiopathic uveitis.

Diagnosing uveitis is like solving a complex puzzle. Because the inflammation is hidden inside the eye, doctors rely on a combination of high-tech imaging, microscopic examinations, and targeted blood tests to identify the type of uveitis you have and its underlying cause.

The Slit-Lamp Exam: Measuring Inflammation

The most common tool your ophthalmologist uses is the slit-lamp, a specialized microscope that allows them to see inside your eye. During this exam, they look for specific markers of inflammation:

Cells and Flare (The SUN Criteria)

Doctors use a standardized system called the SUN criteria (Standardization of Uveitis Nomenclature) to “grade” your inflammation on a scale of 0 to 4+ [1][2].

  • Cells: These are individual white blood cells floating in the fluid of your eye. Think of them like “dust motes” caught in a beam of light. A grade of 4+ means the eye is crowded with cells, while 0 means the inflammation is inactive [1][3].
  • Flare: This is a haziness in the fluid caused by proteins leaking from inflamed blood vessels. It looks similar to “headlight beams in a fog” [1][4].

Clinical “Red Flags”

  • Keratic Precipitates (KPs): These are clumps of inflammatory cells that stick to the back of your cornea (the clear front window of the eye) [5]. Large, “mutton-fat” KPs often point toward diseases like Sarcoidosis, while fine, dust-like KPs are more common in viral infections or HLA-B27 related cases [6][7].
  • Synechiae: These are “adhesions” or sticky spots where the iris (colored part) attaches to the lens. These can interfere with how your pupil moves and can increase eye pressure [8][9].

Advanced Imaging: Seeing the Unseen

When inflammation affects the back of the eye, standard exams aren’t enough. Two critical tests provide a “deep dive” into your eye health:

  1. OCT (Optical Coherence Tomography): This is a non-invasive scan that uses light waves to take cross-section pictures of your retina. It is the “gold standard” for detecting Cystoid Macular Edema (CME)—fluid buildup that can blur your central vision [10][11].
  2. Fluorescein Angiography (FA): A yellow dye is injected into your arm, and a special camera takes pictures as the dye travels through the blood vessels in your eye. This test is essential for finding vasculitis (inflamed blood vessels) or areas where the eye isn’t getting enough blood flow [12][13].

The Diagnostic Workup Checklist

Because uveitis can be linked to conditions in the rest of your body, your doctor will likely order a “standard panel” of blood tests. Use this checklist to track your results:

Test Name What It Looks For Why It’s Important
HLA-B27 A genetic marker Linked to back pain and frequent eye flares [14].
RPR / FTA-ABS Syphilis This infection can mimic almost any type of uveitis [15].
QuantiFERON-TB Tuberculosis (TB) Essential to rule out before starting certain treatments [16].
ACE / Lysozyme Sarcoidosis markers High levels may suggest lung or skin-related inflammation [17].
Chest X-ray / CT Lung inflammation Often paired with ACE tests to check for Sarcoidosis [18].

It is common for these tests to come back “negative,” which is often a good sign as it rules out serious systemic diseases. When no cause is found, the condition is called idiopathic uveitis [16].

Common questions in this guide

What do "cells and flare" mean in my eye exam?
Cells are white blood cells floating in your eye fluid, which indicate active inflammation. Flare is a haziness caused by proteins leaking from inflamed blood vessels. Doctors use these signs to grade the severity of your uveitis.
Why do I need blood tests if the inflammation is only in my eye?
Uveitis is frequently linked to systemic conditions or infections elsewhere in your body. Blood tests help your doctor check for underlying triggers like the HLA-B27 genetic marker, sarcoidosis, tuberculosis, or syphilis.
What does an OCT scan look for in uveitis?
An OCT scan is a non-invasive imaging test that takes detailed cross-section pictures of your retina. For uveitis patients, it is primarily used to detect macular edema, which is fluid buildup that can blur your central vision.
What does it mean if all my uveitis blood tests come back negative?
Negative blood tests are very common and are often a positive sign, as they rule out serious systemic diseases and infections. When your eye is inflamed but no underlying bodily cause is found, it is diagnosed as idiopathic uveitis.
What are synechiae and why are they dangerous?
Synechiae are sticky spots or adhesions where the colored part of your eye (the iris) attaches to the lens behind it. These adhesions can prevent your pupil from moving normally and can cause a dangerous increase in eye pressure.

Questions to Ask Your Doctor

Curated prompts to bring to your next appointment.

  1. 1.What was my SUN grade for 'cells' and 'flare' at today’s exam, and how does it compare to my last visit?
  2. 2.Did my OCT scan show any signs of macular edema or thinning that we need to monitor?
  3. 3.On the Fluorescein Angiography, did you see any signs of 'vasculitis' or 'leakage' in my blood vessels?
  4. 4.Are the 'keratic precipitates' in my eye described as 'mutton-fat' or 'fine,' and what does that suggest about the cause of my uveitis?
  5. 5.Are my synechiae (adhesions) extensive enough that I am at risk for a spike in eye pressure or glaucoma?

Questions For You

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References

References (18)
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    Pediatric uveitis: A comprehensive review.

    Maleki A, Anesi SD, Look-Why S, et al.

    Survey of ophthalmology 2022; (67(2)):510-529 doi:10.1016/j.survophthal.2021.06.006.

    PMID: 34181974
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    Discrepancies in assessing anterior chamber activity among uveitis specialists.

    Yeo TH, Ilangovan S, Keane PA, et al.

    Japanese journal of ophthalmology 2016; (60(3)):206-11 doi:10.1007/s10384-016-0438-0.

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    West Indies Glaucoma Laser Study (WIGLS) 3. Anterior Chamber Inflammation Following Selective Laser Trabeculoplasty in Afro-Caribbeans with Open-angle Glaucoma.

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    Correlation of Clinical Aqueous Flare Grading to Semi-Automated Flare Measurements Using Laser Flare Photometry.

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    Sympathetic Ophthalmia Following an Evisceration Surgery-A Case Report.

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    Bilateral Panuveitis and Exudative Retinal Detachments Associated with Alpelisib.

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    Anterior uveitis onset after bnt162b2 vaccination: is this just a coincidence?

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    Optical Coherence Tomography Findings in Infectious Posterior Uveitis.

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    Discrepancies between Spectral Domain Optical Coherence Tomography and Fluorescein Angiography in Detecting Uveitic Macular Edema.

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    Syphilitic Uveitis With Diverse Clinical Presentations: Multimodal Imaging as a Useful Adjunctive Tool for Diagnosis and Treatment.

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    Etiological and Clinical Characteristics of HLA-B27-associated Uveitis in a Tertiary Referral Center

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    Contribution of diagnostic tests for the etiological assessment of uveitis, data from the ULISSE study (Uveitis: Clinical and medicoeconomic evaluation of a standardized strategy of the etiological diagnosis).

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    Diagnostic Value of Serum-Soluble Interleukin 2 Receptor Levels vs Angiotensin-Converting Enzyme in Patients With Sarcoidosis-Associated Uveitis.

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This page explains uveitis diagnostic testing and terminology for educational purposes only. Always consult your ophthalmologist to interpret your specific exam results and blood work.

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