Conditions

What is intermediate uveitis?

Intermediate uveitis (IU) is a form uveitis characterized by inflammation primarily involving the vitreous (vitritis), the jelly-like substance filling the posterior cavity of the eye. The disease is more frequent in young patients typically in their teens to their forties and does not show any gender predilection.

The main finding is vitritis, with minimal or no signs of anterior segment inflammation.

Vitreous snowball opacities are globular yellow-grey inflammatory aggregates, typically seen in the inferior part of the eye.

They are a very characteristic finding in IU.

Sometimes, in more chronic or aggressive cases, a ‘snowbank’, a grey-white fibrotic membrane, may also be seen in the far periphery of the retina.

The disease can cause inflammation of the retinal vessels (vasculitis) and the main reason for reduction in vision is macular oedema (accumulation of fluid within the central retina).

What causes intermediate uveitis?

Intermediate uveitis has been associated with various aetiologies, including inflammatory and infectious diseases. However, in two thirds of patients no cause can be found, and the disease is labelled as ‘idiopathic’, meaning that no aetiology has been detected. In such cases it is also called Pars Planitis.

Evidence of systemic disorders can be found in up to one third of the patients, including multiple sclerosis, sarcoidosis and inflammatory bowel diseases. Most common infectious aetiologies include tuberculosis, syphilis and Lyme disease.

What are the symptoms?

Most of the patients with intermediate uveitis are asymptomatic. Visual acuity is often preserved.

However, patients can complain of

Diagnosis

The diagnosis of intermediate uveitis is mainly based on ocular manifestations. Although approximately two thirds of patients have an idiopathic disease, the initial diagnostic evaluation should aim to rule out systemic associations and exclude infectious diseases and lymph proliferative disorders.

A minimum workup should include angiotensin-converting enzyme (ACE) level and chest x-ray to rule out sarcoidosis. Serologic testing for tuberculosis, syphilis and Lyme disease and brain magnetic resonance (MRI) for multiple sclerosis should be considered depending upon clinical history and physical findings, according to which laboratory and imaging workup can be expanded.

Fundus fluorescein angiography is frequently carried out to detect the inflammatory activity of the disease, assess the inflammation of retinal vessels and the presence of macular oedema, monitor the course of the disease and its response to treatment. Optical coherence tomography (OCT) is valuable in detecting the presence, and monitoring response to therapy in cystoid macular oedema; it also helps identify other inflammatory complications such as epiretinal membranes or macular hole.

Treatment

The intention of therapy is to control the inflammation and prevent the damage to the retina, and consequently the visual loss.

The main indication for treatment is the presence of macular oedema. Exclusion of infectious and inflammatory causes that may be associated with intermediate uveitis is essential before starting the treatment.

If there is an underlying disease, treatment is directed at the cause.

The decision of when treat the disease is still controversial. Indications include decreased in visual acuity or presence of vision-threatening complications, such as macular oedema, but there is no agreement especially about cases with minimal inflammatory signs and relatively good visual acuity. Generally, visual acuity <6/12, macular oedema, dense vitreous inflammation and extensive inflammation of retinal vessels guide the decision of starting the treatment, but also the presence of floaters interfering with patient’s daily activities is considered in clinical practice.

Treatment options include the use of oral medications, usually starting with systemic steroids to induce rapid response, but frequently requiring the addition of immunosuppressive therapy for long-term control and to minimize side effects from prolonged steroid exposure. The use fo biologics such as Adalimumab is possible, but exclusion of Tuberculosis and MS is essential before this therapy can be initiated. In presence of unilateral or asymmetrical involvement, local therapy including steroid devices (Ozurdex and Iluvien), can be used as first modality.

Complications and Prognosis

The disease is typically chronically active or follows a course of intermittent exacerbations punctuated by periods of quiescence.

If not well controlled, given the insidious chronic nature of the disease, patients can develop inflammatory complications leading to decreased visual acuity, including chronic macular oedema, epiretinal membrane, macular hole.

Early detection of intraocular inflammation and proper treatment is the best way of preventing visual loss.

Colour and fluorescein angiography images showing vitreous snowball opacities as yellow-grey inflammatory aggregates in the inferior part of the eye and mild retinal vasculitis.