54.1 Features
Acute retinal necrosis (ARN) is retinitis with occlusive vasculitis caused by a viral infection with an associated high risk of vision loss due to macular involvement, retinal detachment, and optic neuropathy. The most common causes of ARN are varicella zoster and herpes simplex viruses. The American Uveitis Society proposed criteria to establish the clinical diagnosis of ARN. The diagnosis of ARN is based on the presentation of anterior uveitis, vitritis, and the appearance of white- or cream-colored areas of necrotizing retinitis. These areas will often be patchy, can be confluent, and will extend rapidly circumferentially and posteriorly. Retinal detachment is a relatively common side effect of ARN due to diffuse retinal thinning and atrophy and can be seen in up to two-thirds of all patients.
54.1.1 Common Symptoms
May be associated with decreased vision, redness, photophobia, pain, floaters, and flashes. Occasionally, nonocular symptoms of herpetic infection may be present, such as shingles manifesting in the V1 dermatome.
54.1.2 Exam Findings
Anterior chamber findings often reveal cell and keratic precipitates. The vitreous cell is commonly present. Fundus examination will show multiple white- or cream-colored patches of retinitis. Often, intraretinal hemorrhages will be interspersed with retinitis. Vitreous haze is often present, especially in those with a normal immune system (▶ Fig. 54.1). Occlusion of retinal arteries is commonly seen. Atrophic areas of the retina can be seen in those who present with several weeks of symptoms. Retinal detachments can be also seen and are particularly high risk when extensive areas of atrophy are present. Bilateral involvement is common.
Fig. 54.1 Fundus photograph of the patient with acute retinal necrosis. Vitreous haze prevents a clear view of the retina. Confluent whitening of the retina is present with intraretinal hemorrhage.
54.2 Key Diagnostic Tests and Findings
54.2.1 Optical Coherence Tomography
Optical coherence tomography may demonstrate areas of increased reflectivity in areas of retinal necrosis as well as possible focal hyper-reflective foci in the posterior vitreous, representing areas of vitritis.
54.2.2 Fluorescein Angiography or Ultra-Widefield Fluorescein Angiography
Fluorescein angiography/ultra-widefield fluorescein angiography provides feedback related to overall vascular leakage and extent of nonperfusion. This imaging tool may also be helpful for evaluating treatment response or clinical worsening. Extensive vascular leakage may be present along with nonperfusion in the areas of affected retina.
54.2.3 Fundus Photography
Monitoring early treatment response or clinical worsening can be challenging. Fundus photography, particularly ultra-widefield imaging, can facilitate disease response to therapeutic intervention and to follow for clinical worsening as well (▶ Fig. 54.2, ▶ Fig. 54.3).
Fig. 54.2 Ultra-widefield fundus photography of immune-compromised patient with varicella zoster virus acute retinal necrosis. Diffuse confluent retinitis is present 360 degrees. A clear view usually indicates an immune-compromised host.
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