Congenital and acquired measles infection is caused by a single-stranded RNA virus of the genus Morbillivirus in the Paramyxoviridae family. The virus is highly contagious and is transmitted either directly or via aerosolization of nasopharyngeal secretions to the mucous membranes of the conjunctiva or respiratory tract of susceptible individuals, or transplacentally from a pregnant woman to her fetus.
Despite the existence of an effective vaccine, measles remains a leading cause of mortality worldwide among children. In the United States, however, measles is rare.
Congenital measles infection may cause cataract, optic nerve head drusen, and a bilateral diffuse pigmentary retinopathy involving the posterior pole and retinal periphery. The retinopathy may be associated with normal or attenuated retinal vessels, retinal edema, and macular star formation. Electroretinographic results and visual acuity are usually normal.
The most common ocular manifestations of acquired measles are keratitis and a mild, papillary, nonpurulent conjunctivitis. Corneal scarring in countries with prevalent malnutrition may cause post-measles blindness, a significant problem worldwide.
Measles retinopathy is more common in acquired than in congenital disease, presenting with profound loss of vision 6–12 days after the appearance of the characteristic exanthem; it may be accompanied by encephalitis. Measles retinopathy is characterized by attenuated arterioles, diffuse retinal edema, macular star formation, scattered retinal hemorrhages, blurred disc margins, and clear media. Optic disc pallor and a secondary pigmentary retinopathy with either a bone spicule or salt-and-pepper appearance may subsequently develop.
The differential diagnosis of congenital measles retinopathy includes the TORCH entities, atypical retinitis pigmentosa, and neuroretinitis. For acquired measles retinopathy, considerations include central serous chorioretinopathy, Vogt-Koyanagi-Harada (VKH) syndrome (bullous detachments may resolve, leaving extensive RPE disruption), retinitis pigmentosa, syphilis, and other viral retinopathies.
The diagnosis of measles and its ocular sequelae is made clinically and through serologic testing. Systemic corticosteroids should be considered in cases of acute measles retinopathy.
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Subacute sclerosing panencephalitis
Subacute sclerosing panencephalitis (SSPE) is a rare, late complication of acquired measles infection. It most often affects unvaccinated children 6–8 years after the primary infection. In late childhood or adolescence, visual impairment, behavioral disturbances, and memory impairment may insidiously develop, followed by myoclonus and progression to spastic paresis, dementia, and death within 1–3 years.
Ocular findings are reported in up to 50% of patients with SSPE and may precede the neurologic manifestations by several weeks to 2 years. The most consistent finding is a maculopathy, consisting of focal retinitis and RPE changes, occurring in 36% of patients (Fig 11-14). Retinitis may progress to involve the peripheral retina. Other findings include disc swelling and papilledema, optic atrophy, macular edema, macular pigment epithelial disturbances, small intraretinal hemorrhages, gliotic scar, whitish retinal infiltrates, serous macular detachment, drusen, preretinal membranes, macular hole, cortical blindness, hemianopsia, horizontal nystagmus, and ptosis. Characteristically, there is little, if any, vitritis.
Figure 11-14 Fundus photograph of subacute sclerosing panencephalitis macular retinitis.
(Courtesy of Emad B. Abboud, MD.)
The diagnosis is based on clinical examination, electroencephalographic abnormalities, raised IgG antibody titer against measles in the plasma and cerebrospinal fluid, and/or panencephalitis found on magnetic resonance imaging or brain biopsy.
The differential diagnosis of the ophthalmic findings includes necrotizing viral retinitis caused by HSV, VZV, and CMV infection. Intermediate uveitis and retinal vasculitis associated with multiple sclerosis (MS) may also be considered. Definitive treatment of SSPE remains undetermined.
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Excerpted from BCSC 2020-2021 series: Section 9 - Uveitis and Ocular Inflammation. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.