Introduction:
Urayama described the disease in 1971 in Japan. Often acute retinal necrosis is seen in immunocompetent individuals; however, it can also be seen in immunocompromised individuals and can be unilateral or bilateral. Acute retinal necrosis causes peripheral necrotizing retinitis due to infection with a varicella-zoster virus or herpes simplex virus. If it is bilateral, then it is called bilateral acute retinal necrosis.
What Is the Cause of Acute Retinal Necrosis?
Acute retinal necrosis is caused by the herpes virus family, such as the varicella-zoster, herpes simplex virus, cytomegalovirus (rarely), and Epstein Barr virus. The most common is the varicella-zoster virus.
What Is the Epidemiology of Acute Retinal Necrosis?
It is common in immunocompetent individuals. It affects males and females equally. Herpes simplex virus-induced acute retinal necrosis usually occurs in younger individuals with a history of herpetic encephalitis. Acute retinal necrosis is common in individuals on long-term corticosteroids, noncorticosteroid immunosuppressants, and chemotherapeutics. It is also seen in individuals with AIDS (acquired immunodeficiency syndrome).
What Is the Pathophysiology of Acute Retinal Necrosis?
Acute retinal necrosis occurs when the virus infects the retinal cells, which leads to necrosis. The necrosis is caused due to virally induced cytolysis and choriocapillaris and arterial occlusion. These necrotic cells enter the vitreous chamber, devoid of retinal cells. In the acute phase, the virus particles cause an inflammatory event, followed by a response that damages the retinal cells. Inflammation of the arterioles causes vaso-occlusive events leading to rapid necrosis of the retinal tissue. Retinal necrosis leads to numerous breaks in the pattern of the sieve and breaks on the margin of the normal and inflamed retina. This is followed by retinal detachment. Retinal detachment is seen in almost 75% of the cases of acute retinal necrosis within three months of the onset of symptoms. Proliferative vitreoretinopathy and vitreous traction complicate the retinal detachment in acute retinal necrosis, which reduces surgical success. The breaks are often located peripherally and posteriorly.
What Are the Signs and Symptoms of Acute Retinal Necrosis?
Individuals will often present with ocular pain, which is rapid in onset. They may also present with periocular pain, pain while moving the eye, photophobia or light sensitivity, redness, floaters, decreased vision, blurred vision, and constriction of the visual field. The individual's medical history includes immune status, risk factors for AIDS, systemic or ocular therapy or surgery, previous herpetic infection including encephalitis, and systemic diseases. Previous medical documents should be thoroughly examined. The ocular examination evaluates the anterior chamber and vitreous cells, scleral depression, intraocular pressure, and a dilated retinal examination with indirect ophthalmoscopy. The healthcare provider may find occlusive arteritis and prominent inflammatory reactions in the anterior and vitreous chambers. The posterior pole is unaffected in the early course of the disease. Additional findings may include scleritis, conjunctival injection, increased intraocular pressure, retinal hemorrhage, sheathed retinal arterioles, retinal detachment, and optic disc edema. A typical case involves severe anterior segment inflammation and fibrin, with or without posterior synechiae. The media appears hazy because of the haze in the anterior segment and vitritis with or without cataracts. The fundus examination may reveal peripheral yellow areas of retinitis and disc edema, which subsequently becomes confluent. Retinal hemorrhage is not very prominent.
How Is Acute Retinal Necrosis Evaluated?
Acute retinal necrosis is often clinically diagnosed, and treatment should not be delayed. The acute retinal necrosis triad consists of the following:
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Arteritis phlebitis of the choroidal and retinal vasculature.
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Confluent, necrotizing retinitis that affects the peripheral retina.
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Moderate - severe vitritis.
Clinical characteristics as prescribed by the American uveitis society criteria involve:
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Focal well-demarcated areas of retinal necrosis are situated in the peripheral retina (exterior of the temporal vascular arcades).
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Rapid and circumferential progression of necrosis (in cases where antiviral therapy has not been done).
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Occlusive vasculopathy.
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Inflammatory reaction in the vitreous and anterior chamber.
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Supporting clinical criteria include pain, scleritis, and optic atrophy or neuropathy.
To examine the involved area, three zones have been described:
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Retinitis at zone 1- 3000 microns at the center of fovea1500 microns at margins of the optic disc is sight-threatening.
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Zone 2 lies between zone 1 and the clinical equator between the anterior margin of the vortex ampulla.
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Zone 3 lies anterior to zone 2 till the ora serrata.
In individuals with clinical findings of acute retinal necrosis, the physician may consider a complete blood count with liver and renal function test along with HIV (human immunodeficiency virus) testing, RPR (rapid plasma reagin), FTA-ABS (fluorescent treponemal antibody absorption), erythrocyte sedimentation rate, purified protein derivative sedimentation rate (PPD), and chest radiograph.
What Is the Treatment for Acute Retinal Necrosis?
Treatment is provided in an inpatient or outpatient setting. Around 75 percent of the cases were resolved with Acyclovir. However, treatment does not resolve the retinal detachment of the individual. Acyclovir is started with 10 to 13 mg per kg every 8 hours or 1500mg / m2 /day intravenously for five to ten days. This is followed by taking Acyclovir 800mg five times daily for three months. Their cases included treatment with intravenous Acyclovir 1500mg/m2/day, coumadin or oral aspirin, and oral steroids after starting Acyclovir. Other treatments include:
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Valacyclovir 1000 to 2000 mg for every eight hours orally. This avoids intravenous access.
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Famciclovir should be given 500 mg orally every 8 hours.
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Valganciclovir may be started at 900 mg twice daily for three weeks, followed by 900 mg once daily.
What Is the Differential Diagnosis of Acute Retinal Necrosis?
The differential diagnosis includes:
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CMV retinitis features clear media, immunocompromised individuals, prominence hemorrhage, and early inclusion of the posterior pole in granular CMV retinitis with periphery involvement.
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Progressive outer retinal necrosis with specific characteristics such as no vitritis, outer retinal involvement, outer retinal involvement, early involvement of posterior pole, minimum retinal hemorrhage, and perivascular clear area.
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Syphilis with granulomatous inflammation, posterior placoid chorioretinitis, retinal arterial involvement, round vitreous opacities, and skin changes in the palms and feet.
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Toxoplasmosis is characterized by extreme vitritis, the "headlight in the fog” phenomenon in focal retinitis.
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Behcet disease includes aphthous ulcers, skin and genital lesions, panuveitis, media haze, and vasculitis.
Conclusion
Acute retinal necrosis causes peripheral necrotizing retinitis due to infection with a varicella-zoster virus or herpes simplex virus. Prompt diagnosis may help save vision. Healthcare providers detecting the herpes simplex virus in the eye should immediately refer the individual to an ophthalmologist who may improve visual outcomes.
