Cytomegalovirus (CMV) is a ubiquitous herpesvirus that infects over 90% of humans by 80 years of age. Spread of CMV occurs through the sharing of saliva, ingestion of breast milk, or sexual contact. CMV causes subclinical infection in children and a nonspecific febrile illness lasting 1–3 weeks in adults. A viremia transmits the virus to the bone marrow, where it becomes latent in CD34+ myeloid progenitor cells until these cells are activated, which allows expression and shedding of the virus.
Cytomegalovirus has been most commonly associated with a sectoral, necrotizing retinitis that is seen almost exclusively in AIDS and other immunocompromised states. Few anterior segment complications were previously associated with CMV retinitis, with the exception of thin stellate keratic precipitates. In rare cases, epithelial and stromal CMV keratitis have been described, usually when CMV infection was undiagnosed prior to keratoplasty. However, CMV has been increasingly identified as a significant cause of anterior uveitis and corneal endotheliitis (Fig 9-17). This is probably due, in part, to improved diagnostic acumen. The anterior uveitis is characterized by an acute or chronic iritis, with moderate to severe rises in IOP that are variably responsive to topical corticosteroids. The addition of keratic precipitates, endothelial cell loss, and diffuse or local corneal edema suggests CMV endotheliitis. These presentations are often misdiagnosed as HSV-related endotheliitis, trabeculitis, or Posner-Schlossman syndrome and can be distinguished only by their response to therapy and by results of laboratory investigation.
Laboratory confirmation of CMV-associated anterior segment disease is usually accomplished through PCR testing of aqueous humor for CMV. Aqueous humor is obtained by an anterior chamber tap, which must be performed during an episode of active disease for greatest yield. Concurrent serum testing should also be performed to rule out a systemic viremia as a cause of intraocular detection. In addition, concomitant testing for other herpesviruses can be performed. CMV-associated anterior segment disease may also be diagnosed through histologic examination of corneal biopsy or surgical specimens.
Cytomegalovirus-associated anterior segment disease is treated with ganciclovir and is not responsive to famciclovir, acyclovir, or its derivatives. Resistance of a presumed HSV infection to these agents should raise suspicion for CMV. The optimal treatment of CMV-associated anterior segment disease is unknown, but treatment with oral valganciclovir 900 mg twice daily (with the possibility of lower maintenance dosing) is effective. Valganciclovir may be poorly tolerated and, unfortunately, recurrence of disease with withdrawal of the medication is common. Alternatives include ganciclovir implants and topical ganciclovir, which has demonstrated therapeutic effects when used as an adjunct to systemic therapy and when used in a maintenance role. Recurrence is possible after keratoplasty. The role of corticosteroids is unclear, as there is some suggestion that corticosteroid use may prolong or worsen CMV-associated anterior segment disease. Corticosteroids should therefore be used judiciously in this setting.
Figure 9-17 Clusters of keratic precipitates in cytomegalovirus corneal endotheliitis.
(Courtesy of Cornea Service, Paulista School of Medicine, Federal University of São Paulo.)
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Excerpted from BCSC 2020-2021 series: Section 10 - Glaucoma. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.