Diagnosis and Management of Acute Retinal Necrosis

    • CE credits 2 hours
    • COPE code 67273-PS / 119240
    • Available until Apr 2, 2023

Introduction

Learning Objectives

  • To review the differential diagnosis of acute retinal necrosis and compare it to other infections of the retina and uvea.
  • To review the management of acute retinal necrosis.
  • To provide recommendations on which clinical presentations and exams should be considered when acute retinal necrosis is suspected.

CASE

A 65-year-old man presented to the emergency department with a 3-day history of decreased vision in his right eye associated with redness, pain, photophobia, and increased floaters. Over the past few days he felt his symptoms were getting worse. He was otherwise healthy with no significant ocular history. He denied any history of immunosuppression. He was monogamous and denied any history of sexually transmitted diseases. Of note, he had a remote history of V1 shingles eight years ago.

On examination his visual acuity was 20/100 (right eye) and 20/20 (left eye). There was no improvement with the use of a pinhole occluder. There was no relative afferent defect on examination. Intraocular pressures were 8 and 16 mm of Hg by Tonopen respectively. Slit lamp examination of the right eye demonstrated 3+ injection, 2+ chemosis, 2+ anterior chamber cell, 2+ flare, large keratic precipitates clustered inferiorly and centrally on the endothelium (Arlt’s Triangle), a normal iris, and 1+ nuclear sclerosis. Slit lamp examination of the left eye demonstrated 1+ nuclear sclerosis. Dilated fundus examination of the right eye revealed grade 2 vitreous haze, 4+ cell, a partially swollen and numerous yellowish pale areas of retinal. In addition, peri-vascular retinal hemorrhages. Dilated fundus examination of the left eye was within normal limits.

Quick Question

The history and photograph are most consistent with which of the following:

  • Cytomegalovirus (CMV) retinitis

    Cytomegalovirus (CMV) retinitis is a serious vision-threatening eye condition that is seen in patients who are immunosuppressed.1,2 Classically it was an AIDS-related opportunistic infection that occurred in high frequency prior to the advent of antiretroviral therapy, more commonly when CD4 counts are less than 50. Its incidence has been decreasing in the developed world, although it still remains prevalent in the developing world. It is also seen in severe immunosuppression from chemotherapy or in the context of immune modulating therapy for autoimmune conditions. It is caused by cytomegalovirus, a double stranded DNA virus in the herpesviridae family, which reaches the retina hematogenously. Immunosuppression permits uncontrolled CMV replication. It may mimic ARN as it presents as with vitritis (inflammation of the vitreous), retinial vasculitis (inflammation of the retinal vessels which clinically appears as sheathing) and peripheral retinitis (inflammation of the retina which clinically appears as retinal whitening). However, it differs, principally from ARN, in that it exclusively affects the immunocompromised (ARN primarily affects the immunocompetent), has less vitritis, mainly periphebitis (mostly affects retinal venules where ARN affects arterioles), more posterior retinitis, and hemorrhages are very prominent (pizza pie appearance). Compared to ARN and PORN, CMV typically progresses more slowly. Viral PCR is often performed to confirm the diagnosis. Previously, CMV retinitis was treated with intravenous induction therapy with ganciclovir followed by maintenance therapy. Due to the cost, risk of sepsis, and the quality of life associated with an indwelling catheter, the oral formulation of valgancyclovir was developed. A randomly controlled trial was performed in 2002 which demonstrated oral valganciclovir was non-inferior to intravenous ganciclovir for induction treatment.3

  • Acute retinal necrosis (ARN)
     
    CORRECT

     

  • Progressive outer retinal necrosis (PORN)

    Progressive outer retinal necrosis (PORN) is a rapidly progressive herpetic retinopathy with features that make it its own distinct entity from ARN.4 As with ARN, PORN represents a reactivation of a latent herpes (VZV) infection. PORN differs principally from ARN in that it is a disease of the immunocompromised, particularly HIV infected patients. This difference leads to the distinct clinical presentation of a minimal inflammatory retinitis (with minimal or no vitritis) in PORN, compared to the exuberant response in ARN as the immunosuppressed individuals with PORN are unable to mount a significant immune response.Thus, patients with PORN are typically asymptomatic. Additionally, PORN typically presents as retinitis in the posterior pole of the retina, whereas ARN affects the anterior peripheral retina. PORN is treated similarly to ARN with antiviral therapy until the immune system is reconstituted.

  • Toxoplasma chorioretinitis

    Toxoplasma choroiditis is the most common cause of posterior uveitis (inflammation affecting the “back” of the uvea, called the choroid) worldwide.5 The causative agent is toxoplasma gondii, a parasitic protozoon that exists in an oocyte form (filled with sporozoites) or cyst form (filled with bradyzoites). Sporozoites and bradyzoites can then transform into actively dividing tachyzoites which may proliferate in nucleated cells, thus protecting them from the host immune system. These organisms may lay dormant for years before stress prompts recurrent activity; this typically presents in the retina as an area of retinitis adjacent to an old scar. Most cases are acquired congenitally due to a pregnant woman being exposed to contaminated uncooked meat, or cat feces. Toxoplasma chorioretinitis may mimic ARN in that the host is immunocompromised, there is significant vitritis, and an area of retinitis. Toxoplasma chorioretinitis differs, however, as the retinitis typically presents adjacent to an old chorioretinal scar. Serum serology or aqueous PCR can be performed to support the diagnosis. The classic antibiotic triple therapy involves oral pyrimethamine, sulfadiazine, and folinic acid, however other antibiotics can be used with success.

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