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Ophthalmology – Acute Retinal Necrosis (Necrotizing Herpetic Retinitis)
Acute retinal necrosis is a severe, vision-threatening infectious retinitis caused by members of the herpes virus family, most commonly varicella zoster virus and herpes simplex virus. It is characterized by a combination of anterior uveitis, vitritis, and rapidly progressive peripheral retinal necrosis that spreads circumferentially and posteriorly, often accompanied by occlusive retinal vasculitis and a high risk of retinal detachment. Despite being a rare condition, with an estimated incidence of approximately 1 case per 1.6–2.0 million individuals, it typically affects otherwise healthy, immunocompetent individuals and shows a bimodal age distribution, most commonly occurring around ages 20 and 50.
Risk factors include a history of herpetic infections such as herpes simplex keratitis, herpes zoster ophthalmicus, cold sores, chickenpox, encephalitis, or shingles. Although immunodeficiency may contribute, most cases occur in immunocompetent patients. Genetic predispositions have been described, with certain HLA types associated with different populations and disease severity. The pathophysiology involves reactivation or primary infection of herpes viruses, which travel via axonal pathways to the retina, leading to viral replication within retinal cells. This results in full-thickness retinal necrosis, intranuclear viral inclusions, and both granulomatous and non-granulomatous inflammation affecting ocular tissues.
Patients may initially present with relatively mild symptoms such as eye redness, irritation, photophobia, floaters, and periorbital pain, although many experience sudden vision loss. On examination, there is often evidence of anterior uveitis, including keratic precipitates and inflammatory activity in the anterior chamber, as well as vitritis. Within days, characteristic posterior segment findings develop, including multifocal, well-demarcated patches of yellow-white retinal necrosis in the peripheral retina. These lesions rapidly progress circumferentially and posteriorly, often sparing the macula initially. Retinal vasculitis with vascular sheathing and hemorrhages may also be present. Over time, complications such as proliferative vitreoretinopathy lead to retinal breaks and rhegmatogenous retinal detachment, which occurs in more than half of cases, typically within one to two months. Bilateral involvement is seen in about 20% of patients at presentation, and without treatment, the second eye may become affected within months.
Diagnosis is primarily clinical, guided by established criteria that include peripheral retinal necrosis, rapid progression, occlusive vasculopathy, and significant intraocular inflammation. Laboratory confirmation can be achieved using polymerase chain reaction testing of aqueous or vitreous samples, which provides high sensitivity and specificity for identifying viral DNA. Other diagnostic methods, such as antibody testing or cultures, may support the diagnosis but are less definitive. Serial fundus photography is useful for monitoring disease progression, and careful examination of both eyes is essential due to the risk of bilateral spread.
The differential diagnosis includes other infectious and inflammatory retinal conditions such as progressive outer retinal necrosis, cytomegalovirus retinitis, toxoplasmosis, syphilitic retinitis, Behçet disease, sarcoidosis, intraocular lymphoma, and fungal endophthalmitis. Management requires urgent antiviral therapy to limit retinal destruction and reduce complications. Treatment traditionally involved intravenous acyclovir followed by prolonged oral therapy, but newer regimens include oral antivirals such as valacyclovir or famciclovir, often combined with intravitreal antiviral injections such as foscarnet or ganciclovir. Adjunctive corticosteroids are frequently used to control inflammation, and topical steroids are commonly administered for anterior segment involvement.
Patients should be urgently referred to a retinal or uveitis specialist due to the aggressive nature of the disease and the potential need for surgical intervention. Prophylactic laser retinopexy may be considered to reduce the risk of retinal detachment, although its benefit remains debated. Vitrectomy is indicated in cases of dense vitreous opacities, hemorrhage, or established retinal detachment. Close monitoring is essential, particularly during the early course, to detect progression, bilateral involvement, or complications.
The prognosis remains guarded despite advances in antiviral therapy, with many patients experiencing significant vision loss. Retinal detachment is the most common and serious complication, and visual outcomes are often poor, with a substantial proportion of patients developing vision worse than 20/200 over time. Other complications include optic nerve involvement, vitreous hemorrhage, retinal neovascularization, and eventual blindness. Early recognition and aggressive treatment are critical to improving outcomes and preserving vision.
Acute retinal necrosis is a severe, vision-threatening infectious retinitis caused by members of the herpes virus family, most commonly varicella zoster virus and herpes simplex virus. It is characterized by a combination of anterior uveitis, vitritis, and rapidly progressive peripheral retinal necrosis that spreads circumferentially and posteriorly, often accompanied by occlusive retinal vasculitis and a high risk of retinal detachment. Despite being a rare condition, with an estimated incidence of approximately 1 case per 1.6–2.0 million individuals, it typically affects otherwise healthy, immunocompetent individuals and shows a bimodal age distribution, most commonly occurring around ages 20 and 50.
Risk factors include a history of herpetic infections such as herpes simplex keratitis, herpes zoster ophthalmicus, cold sores, chickenpox, encephalitis, or shingles. Although immunodeficiency may contribute, most cases occur in immunocompetent patients. Genetic predispositions have been described, with certain HLA types associated with different populations and disease severity. The pathophysiology involves reactivation or primary infection of herpes viruses, which travel via axonal pathways to the retina, leading to viral replication within retinal cells. This results in full-thickness retinal necrosis, intranuclear viral inclusions, and both granulomatous and non-granulomatous inflammation affecting ocular tissues.
Patients may initially present with relatively mild symptoms such as eye redness, irritation, photophobia, floaters, and periorbital pain, although many experience sudden vision loss. On examination, there is often evidence of anterior uveitis, including keratic precipitates and inflammatory activity in the anterior chamber, as well as vitritis. Within days, characteristic posterior segment findings develop, including multifocal, well-demarcated patches of yellow-white retinal necrosis in the peripheral retina. These lesions rapidly progress circumferentially and posteriorly, often sparing the macula initially. Retinal vasculitis with vascular sheathing and hemorrhages may also be present. Over time, complications such as proliferative vitreoretinopathy lead to retinal breaks and rhegmatogenous retinal detachment, which occurs in more than half of cases, typically within one to two months. Bilateral involvement is seen in about 20% of patients at presentation, and without treatment, the second eye may become affected within months.
Diagnosis is primarily clinical, guided by established criteria that include peripheral retinal necrosis, rapid progression, occlusive vasculopathy, and significant intraocular inflammation. Laboratory confirmation can be achieved using polymerase chain reaction testing of aqueous or vitreous samples, which provides high sensitivity and specificity for identifying viral DNA. Other diagnostic methods, such as antibody testing or cultures, may support the diagnosis but are less definitive. Serial fundus photography is useful for monitoring disease progression, and careful examination of both eyes is essential due to the risk of bilateral spread.
The differential diagnosis includes other infectious and inflammatory retinal conditions such as progressive outer retinal necrosis, cytomegalovirus retinitis, toxoplasmosis, syphilitic retinitis, Behçet disease, sarcoidosis, intraocular lymphoma, and fungal endophthalmitis. Management requires urgent antiviral therapy to limit retinal destruction and reduce complications. Treatment traditionally involved intravenous acyclovir followed by prolonged oral therapy, but newer regimens include oral antivirals such as valacyclovir or famciclovir, often combined with intravitreal antiviral injections such as foscarnet or ganciclovir. Adjunctive corticosteroids are frequently used to control inflammation, and topical steroids are commonly administered for anterior segment involvement.
Patients should be urgently referred to a retinal or uveitis specialist due to the aggressive nature of the disease and the potential need for surgical intervention. Prophylactic laser retinopexy may be considered to reduce the risk of retinal detachment, although its benefit remains debated. Vitrectomy is indicated in cases of dense vitreous opacities, hemorrhage, or established retinal detachment. Close monitoring is essential, particularly during the early course, to detect progression, bilateral involvement, or complications.
The prognosis remains guarded despite advances in antiviral therapy, with many patients experiencing significant vision loss. Retinal detachment is the most common and serious complication, and visual outcomes are often poor, with a substantial proportion of patients developing vision worse than 20/200 over time. Other complications include optic nerve involvement, vitreous hemorrhage, retinal neovascularization, and eventual blindness. Early recognition and aggressive treatment are critical to improving outcomes and preserving vision.
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