W ithin the vitreous cavity, vitritis, snowballs especially suggestive of sarcoidosis and intermediate uveitis , 18 fibrosis or cyclitic membranes may be present. The location of white cells in the vitreous can help pinpoint the source of inflammation. In iridocyclitis, cells are located more anteriorly, while in intermediate or posterior uveitis, cells are more distributed or appear posteriorly.
Snowbanking overlying the ora serrata can occasionally occur. Differential Diagnosis. Classification can help to rapidly narrow the differential diagnosis. While much overlap occurs, many etiologies are strongly linked to certain uveitis classes. For example, HLA-B27 positivity is characteristic of acute anterior uveitis, whereas toxoplasmosis is associated with a posterior uveitis.
Along with the classification of uveitis, other important clues to the differential include ethnicity and exposure history. Lab Testing and Imaging. Tailor lab testing to the clinical situation. Most cases of unilateral, nongranulomatous anterior uveitis do not need a laboratory workup. More complex situations may require testing tailored to the patient. Table 3 lists recommended laboratory tests for the different suspected etiologies of uveitis.
The most appropriate way to approach laboratory testing is to form a differential diagnosis and then customize the testing accordingly. However, nearly every lab panel for uveitis should include testing for syphilis, sarcoidosis and TB. Testing can also include optical coherence tomography to evaluate for cystoid macular edema and choroidal thickness if enhanced depth imaging is available Figure 1 ; fluorescein angiography to assess for vascular leakage and serous retinal detachments; and ultrasonography to evaluate for posterior scleritis.
Another option is scanning laser ophthalmoscopy Figure 2. Systemic imaging, such as chest X-ray and CT scan, can be helpful when sarcoidosis is suspected.
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In cases unresponsive to treatment or in which infectious or neoplastic causes are suspected, diagnostic vitrectomy or chorioretinal biopsy may help increase diagnostic certainty. Treatment for Uveitis. This often requires either antimicrobial or immunomodulatory agents. These agents are first-line therapy in most cases of noninfectious uveitis and are especially helpful in anterior uveitis.
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The rule of thumb is to use the safest, most potent agent Table 4, page Most clinicians start with prednisolone acetate. Assess IOPs in any patient on topical steroids at least two weeks after beginning the steroid. Monitor any patient with a history of steroid response closely. This can be given every month and titrated to patient response. Triamcinolone can also be administered intravitreally and should last weeks to months. Another intravitreal option is the dexamethasone degradable implant Ozurdex, Allergan , which lasts one to three months.
In cases that involve anterior inflammation, a cycloplegic will also prevent ciliary spasm and help ameliorate photophobia. In addition, movement and deepening of the iris help to prevent the formation of posterior and anterior synechiae. Severe uveitis of any location or posterior uveitis may warrant oral or intravenous c. Any patient on more than two weeks of systemic steroids requires a taper. Patients should never stay on a dose greater than 7.
Patients on long-term therapy should also receive calcium and vitamin D supplementation. If corticosteroids do not achieve control, immunomodulatory agents are an option. Locally, sirolimus has shown promise as a bimonthly intravitreal therapy. Phase I data showed good control, and the SAVE trial showed it reduced vitreous haze and the need for corticosteroid therapy. The SAKURA study demonstrated that sirolimus reduced ocular inflammation and increased the probability of tapering steroids.
Systemic Therapy. If local immunomodulatory control is inadequate, the patient may need systemic treatment.
Clinicians who are not comfortable using these medications should refer the patient to a uveitis specialist or rheumatologist. Limited data exist, and most providers will base medication choice on familiarity, side-effect profile and comorbidities.
These agents include methotrexate, mycophenolate and azathioprine. If greater control is needed, another antimetabolite or drug from a new class can be added. Adalimumab Humira, Abbvie , a biologic tumor necrosis factor-alpha inhibitor, is approved for noninfectious intermediate, posterior and panuveitis. This is a retrospective observational study where 23 eyes with infectious necrotising retinitis underwent OCT scanning with the Heidelberg HRA Spectralis. Features were compared according to aetiology. The cases were divided into a viral retinitis group, including VZV and CMV retinitis 13 eyes , and a toxoplasmosis group 10 eyes.
The cases were diagnosed clinically, if there was ambiguity in the clinical findings a vitreous tap was performed and the sample underwent PCR testing for confirmation. The common features on OCT of all the eyes examined were full thickness retinitis indicated by full thickness signal hyper-intensity and obscuration of the retinal layers, some degree of vitritis and thickening of the choroid underneath the lesion. The differentiating features found in patients with toxoplasmosis include: large hyper-reflective oval deposits on the retinal surface, retro-hyaloid space and posterior hyaloid surface.
In the toxoplasmosis cases, the underlying choroid showed significant hypo-reflectivity with increased thickening and disruption of the architecture indicated by loss of septae on extended depth imaging scans.
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The differentiating features found in patients with viral retinitis were cystic oedema and hyper-reflective vertical stripes in the outer nuclear layer. These findings may be explained by the pathophysiology of toxoplasmosis chorioretinitis, in that it is highly inflammatory hence the presence of these ovoid deposits in the posterior segment, and that there is a greater involvement of the choroid compared to viral retinitis where there is mild choroidal thickening only.
Once again, this is an observational uncontrolled study in a small number of eyes, however an interesting concept into some differentiating features which could help clinch the diagnosis early in some cases. It does not, however, absolve the need for aqueous humour or vitreous sampling and PCR testing for confirmation, and treatment with intra-vitreal anti-viral medication such as Foscarnet if acute fulminant viral retinal necrosis is suspected.
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