Cytomegalovirus Corneal Endotheliitis

Corneal endotheliitis, first described by Khodadoust and Attarzadeh in 1982, is characterized by corneal edema, keratic precipitates, mild anterior chamber inflammation, and endothelial dysfunction. Classification is based on the distribution of keratic precipitates and associated stromal and epithelial edema, with 4 recognized patterns: linear, sectoral, disciform, and diffuse. Several viruses, including herpes simplex virus (HSV), varicella-zoster virus (VZV), and human herpesvirus 7 (HHV-7), have been implicated in corneal endotheliitis. In 2006, Koizumi reported the first case attributed to cytomegalovirus (CMV). CMV corneal endotheliitis may manifest with linear or coin-shaped keratic precipitates, with or without corneal edema, in immunocompetent individuals. Misdiagnosis is common due to clinical overlap with other viral endotheliitides. Timely and accurate recognition is essential, as delayed antiviral therapy can result in irreversible endothelial cell loss and permanent visual impairment. CMV corneal endotheliitis is an emerging cause of endothelial dysfunction, recurrent anterior uveitis, and secondary glaucoma, with major implications for vision preservation. The corneal pathogenicity of CMV in immunocompetent individuals was first recognized in the early 2000s. Subsequent reports from East Asia, particularly Japan, Taiwan, and Singapore, demonstrated that CMV accounts for a substantial proportion of presumed viral endotheliitis previously attributed to HSV or VZV. In nonendemic regions, the condition is likely underdiagnosed because of limited aqueous humor polymerase chain reaction (PCR) testing, low clinical suspicion, and overlapping clinical features. Accurate recognition is critical, as management strategies differ from other viral etiologies, and inappropriate therapy can result in irreversible endothelial cell loss, corneal decompensation, and permanent visual impairment. The pathogenesis of CMV corneal endotheliitis involves direct viral replication within corneal endothelial cells, inducing cytopathic changes and local immune-mediated inflammation. CMV establishes latency in ocular tissues, with reactivation precipitated by immunosenescence, ocular surgery, corticosteroid exposure, or systemic immune dysregulation. Reactivation results in endothelial barrier dysfunction, stromal hydration, and progressive endothelial loss, amplified by cytotoxic T-cell activity and pro-inflammatory cytokines such as interleukin 6 (IL-6) and tumor necrosis factor α (TNF-α). Trabecular meshwork inflammation may impair aqueous outflow, accounting for the frequent association with ocular hypertension and secondary glaucoma. Surgical procedures, including penetrating keratoplasty, endothelial keratoplasty, and trabeculectomy, as well as long-term corticosteroid use, contribute to a microenvironment that favors viral persistence and reactivation. Clinically, CMV corneal endotheliitis presents as recurrent, unilateral blurred vision, often with halos, glare, or photophobia. The hallmark slit-lamp finding is localized corneal edema with sharply demarcated “coin-shaped” keratic precipitates, although diffuse or granulomatous forms may occur. Anterior chamber inflammation is generally mild to moderate, and iris atrophy can develop in chronic or recurrent cases. Intraocular pressure (IOP) spikes are common during active episodes, and repeated uncontrolled elevations may cause glaucomatous optic neuropathy. The disease follows a chronic, relapsing course with asymptomatic intervals. Differential diagnosis includes HSV and VZV endotheliitis, Fuchs endothelial corneal dystrophy, idiopathic corneal edema, and postsurgical immune reactions such as graft rejection. The gold standard for diagnosis is aqueous humor PCR for CMV DNA, with quantitative PCR providing additional value for viral load assessment and treatment monitoring. Adjunctive tools include specular microscopy to evaluate endothelial cell density (ECD) and morphology, anterior segment OCT (AS-OCT) to monitor corneal thickness and edema resolution, and confocal microscopy (IVCM) to detect endothelial abnormalities and inflammatory infiltration. Limited access to PCR in many settings underscores the importance of clinical suspicion for early recognition. Delayed diagnosis and treatment accelerate endothelial loss and markedly increase the risk of corneal decompensation and keratoplasty. Management of CMV corneal endotheliitis centers on viral suppression and inflammation control. Topical ganciclovir 0.15% gel is the 1st-line agent, applied 5 times daily for induction and tapered to maintenance dosing to reduce recurrence. Systemic valganciclovir is reserved for severe, bilateral, or recurrent disease, typically initiated at 900 mg twice daily and tapered to 450 to 900 mg once daily. Corticosteroids must be used cautiously, always with antiviral coverage, to control inflammation without promoting viral replication. Secondary glaucoma is managed with topical hypotensive agents and, in refractory cases, surgical interventions such as trabeculectomy or glaucoma drainage devices. Endothelial keratoplasty is indicated for irreversible decompensation, although recurrence in grafts is common and requires perioperative antiviral prophylaxis. Long-term follow-up is critical, as relapse is frequent without maintenance therapy, and early detection of reactivation is essential. The prognosis of CMV corneal endotheliitis depends on timely diagnosis and initiation of targeted antiviral therapy. Early recognition and treatment allow many patients to preserve corneal clarity and functional vision, whereas delayed or missed diagnosis often leads to visual loss from corneal decompensation and secondary glaucoma. The chronic, relapsing course underscores the need for patient education, adherence to therapy, and regular monitoring. Optimal outcomes require an interprofessional approach involving ophthalmologists, optometrists, infectious disease specialists, and primary care providers to ensure accurate diagnosis, appropriate antiviral use, monitoring for drug toxicity, and management of comorbidities that predispose to reactivation. Educational initiatives to improve recognition and standardize management can enhance provider competence, improve outcomes, and reduce the burden of this vision-threatening disease.