Acute retinal necrosis overview
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-in-Chief: Luke Rusowicz-Orazem, B.S.
Overview
Historical Perspective
Acute retinal necrosis was first discovered in 1971 by Urayama A, Yamada N, Sasaki T. Acute retinal necrosis was first officially classified as bilateral acute retinal necrosis in 1978 by N.J. Young and A.C. Bird, applied to 4 cases of bilateral necrotizing retinitis that progressed to retinal detachment and phthisis despite corticosteroid and antibiotic therapy. In the 1980s, emergence of pathological and electron findings from analysis of vitrectomy and enucleation specimens led to the discovery of acute retinal necrosis' cause as members of the herpes virus family. The official diagnostic criteria for acute retinal necrosis was proposed by the American Uveitis Society in 1994.
Classification
Acute retinal necrosis may be classified both by staging - Acute or Late - or by severity: Mild or Fulminant.
Pathophysiology
The pathogenesis of Acute retinal necrosis is characterized by retinal inflammation due to ocular viral infection. Particles from Herpes simplex virus 1 (HSV-1), Herpes simplex virus 2 (HSV-2), and Varicella zoster virus (VZV) infiltrate the retina via various locations of epithelial penetration, including the skin, conjunctiva, cornea, and nasal cavity. Acute retinal necrosis develops from HSV-1, HSV-2, and VZV due to the viruses' unique ability to transmit and replicate in the Central Nervous System (CNS), as well as their ability to transport anterograde through the optic nerve, establish latency, reactivate, and cause retinal inflammation. For Caucasian populations: possessing the HLA-DQw7, HLA-Bw62, and HLA-DR4 antigens are correlated to genetic predisposition to ARN. For Japanese populations: possessing the HLA-Aw33, HLA-B44, and HLA-DRw6 antigens are correlated to genetic predisposition to ARN. Acute retinal necrosis is associated with the following ocular conditions: Progressive outer retinal necrosis, Uveitis, Cytomegalovirus retinitis, Toxoplasmic chorioretinitis, and Endophthalmitis.
Causes
Acute retinal necrosis is usually caused by reactivation of latent viruses: Herpes simplex virus 1 & 2, Varicella-zoster virus, cytomegalovirus, and Epstein-Barr virus.
Differentiating Acute retinal necrosis other Diseases
Acute retinal necrosis must be differentiated from other diseases that cause eye pain, conjunctival infection, photophobia, and vision loss.
Epidemiology and Demographics
Research in the United Kingdom resulted in an estimated incidence of approximately 6.3 per 100,000 individuals. Acute retinal necrosis (ARN) developed from Herpes simplex virus 1 and Varicella-zoster virus is most common among patients older than 50 years, while the incidence of HSV-2 caused ARN is highest in children and young adults between age 9 and 22 years. There is no racial or gender predisposition to Acute retinal necrosis.
Risk Factors
The primary risk factors for Acute retinal necrosis include Immunocompromise and immunosuppression from disease and prolonged corticosteroid use. Genetic predisposition for certain caucasian and Japanese populations heightens the possibility of developing Acute retinal necrosis.
Screening
There is no established, diagnostic screening process for Acute retinal necrosis.
Natural History, Complications and Prognosis
Symptoms of Acute retinal necrosis (ARN) develop rapidly upon onset of pathogenic infection. The natural progression of ARN depends on whether the case is mild or fulminant. Mild cases of ARN presents with white-yellow necrotic lesions that do not coalesce or lead to retinal detachment; the disease is self-limited. Fulminant cases of ARN will lead to progressive necrosis of retinal tissue, leading to pigmentation scarring, vitreous debris, and retinal detachment. Without treatment, ARN will usually progress to Bilateral acute retinal necrosis (BARN) within weeks to a few months. Complications resulting from Acute retinal necrosis occur due to retinal tissue damage and subsequent infection from the causative pathogen. Without treatment, the prognosis for Acute retinal necrosis (ARN) varies. Mild ARN is usually self-limited and will resolve itself without treatment; risk of permanent vision loss is very low. Fulminant ARN will usually progress to complications such as progressive outer retinal necrosis and has a worse prognosis. With treatment, the prognosis for ARN is good if the therapy is administered in the early stages and sustained until symptoms resolve.
Diagnosis
Diagnostic Criteria
The American Uveitis Society determined five diagnostic criteria for Acute retinal necrosis in 1994.
History and Symptoms
Patient history of prior or concurrent diseases, particularly those associated with Acute retinal necrosis pathogens, or sources of immunocompromise should be considered in the diagnosis of Acute retinal necrosis. Symptoms of Acute retinal necrosis include eye pain, vision loss, floaters. flashes, excessive sensitivity to light, Flu symptoms, and redness of the affected eye.
Physical Examination
Physical examination for Acute retinal necrosis may reveal erythema and hyperaemia of the retina, white-yellow necrotic lesions, purulent exudate, opaque vitreous, and other indications of inflammation in the eye.
Laboratory Findings
Laboratory findings associated with Acute retinal necrosis are those used to determine the viral pathogen, including PCR test results, viral cultures, immunoflourescence results, and detection of indicative antibodies to sources of Acute retinal necrosis via the Goldmann-witmer coefficient.
Electrocardiogram
There are no diagnostic electrocardiogram findings associated with Acute retinal necrosis.
Chest X Ray
There are no diagnostic chest x ray findings associated with Acute retinal necrosis.
CT
CT imaging may reveal indicators of inflammation and infection by the causative pathogen for Acute retinal necrosis, including hypoattenuation along the optic tract indicative of Varicella-zoster virus (VZV) infection and hyperattenuation along the optic tract, retina, sclerae, and lateral geniculate body.
MRI
MRI imaging may reveal lesions that may be indicative of infection from Acute retinal necrosis pathogens.
Echocardiography or Ultrasound
There are no diagnostic echocardiography or ultrasound findings associated with Acute retinal necrosis.
Other Imaging Findings
Other imaging findings facilitating the diagonsis of Acute retinal necrosis include Fundus Autoflourescence, Fluorescein Angiography, and Optical Coherence Tomography.
Other Diagnostic Studies
There are no other diagnostic studies associated with Acute retinal necrosis.
Treatment
Medical Therapy
The mainstays of medical therapy for Acute retinal necrosis are regimens of empiric and pathogen-directed antimicrobial therapy.
Surgery
Surgery is not the first-line treatment option for patients with Acute retinal necrosis; it is primarily indicated when there is risk of complications, including retinal detachment and tissue atrophy.
Primary Prevention
Preventing onset of Acute retinal necrosis is dependent on preventing the causative infection from Herpes simplex virus (HSV), Varicella-zoster virus (VZV), and Cytomegalovirus (CMV).
Secondary Prevention
While recurrence of Acute retinal necrosis is not completely preventable presently, administration of topical and intravitreal antiviral therapy targeted to the specific etiological cause of the disease can reduce the chance of recurrence.