Pathobiology and treatment of viral keratitis

Keratitis is one of the most prevalent ocular diseases manifested by partial or total loss of vision. Amongst infectious (viz., microbes including bacteria, fungi, amebae, and viruses) and non-infectious (viz., eye trauma, chemical exposure, and ultraviolet exposure, contact lens) risk factors, viral keratitis has been demonstrated as one of the leading causes of corneal opacity. While many viruses have been shown to cause keratitis (such as rhabdoviruses, coxsackieviruses, etc.), herpesviruses are the predominant etiologic agent of viral keratitis. This chapter will summarize current knowledge on the prevalence, diagnosis, and pathobiology of viral keratitis. Virus-mediated immunomodulation of host innate and adaptive immune components is critical for viral persistence, and dysfunctional immune responses may cause destruction of ocular tissues leading to keratitis. Immunosuppressed or immunocompromised individuals may display recurring disease with pronounced severity. Early diagnosis of viral keratitis is beneficial for disease management and response to treatment. Finally, we have discussed current and emerging therapies to treat viral keratitis.

Management of cytomegalovirus corneal endotheliitis

Background

Cytomegalovirus (CMV) can manifest as corneal endotheliitis in immunocompetent individuals. Early diagnosis is prudent to prevent endothelial cell loss, which could ultimately lead to corneal decompensation. CMV DNA was first detected in an eye with corneal endotheliitis in 2006; since then, clinical evidence from numerous case reports and case series have accumulated.

Main text

In this narrative review, we identified several drugs, including ganciclovir, valganciclovir, and their combination in oral, intravenous, intravitreal, and topical forms in different concentrations, together with the judicious use of topical steroids, have reported variable success. There has yet to be any prospective comparative study evaluating the efficacy and safety of these assorted forms of treatment; clinical evidence is based on case reports and case series. CMV endotheliitis presenting with corneal edema can masquerade as other corneal diseases and thus poses a great challenge especially in post-keratoplasty eyes. Heightened awareness is needed before and after keratoplasty to start prompt prophylaxis and treatment.

Conclusion

There is no consensus on the management of CMV endotheliitis. Further studies are much needed to elucidate the optimal treatment modality, regime, and duration in the treatment and prophylaxis of CMV endotheliitis.

Concomitant Varicella Zoster Virus and Cytomegalovirus Corneal Endotheliitis in an Immunocompetent Patient

PURPOSE

To describe an immunocompetent patient with corneal endotheliitis caused by concomitant infection of cytomegalovirus and varicella zoster virus (VZV).

CASE PRESENTATION

A 37-year-old immunocompetent woman was referred to our hospital because of persistent corneal endotheliitis in the left eye. Slit-lamp examination revealed mild conjunctival injection, localized stromal corneal edema with underlying pigmented keratic precipitates, and inferior superficial corneal neovascularization. Anterior chamber examination revealed grade 2+ inflammatory cells. Real-time polymerase chain reaction analysis of aqueous humor supported a diagnosis of concomitant cytomegalovirus and VZV corneal endotheliitis. Treatment comprised oral valganciclovir and oral acyclovir for 6 weeks. During 12 months of follow-up, the cornea was clear, keratic precipitates were absent, and anterior chamber inflammation was resolved. No recurrences were noted.

CONCLUSIONS

Untreated corneal endotheliitis can cause corneal decompensation and permanent endothelial cell loss. Dual infection must be considered in patients with corneal endotheliitis, particularly those with inadequate treatment responses. Timely detection of causative agents and administration of an appropriate treatment regimen can prevent corneal damage.

Clinical Results and Utility of Herpesviruses Multiplex Polymerase Chain Reaction: Assessment of Aqueous Humor Samples From Patients With Corneal Endotheliitis and High Intraocular Pressure

PURPOSE

The main purpose of this study was to evaluate herpesvirus infection in patients with corneal endotheliitis and high intraocular pressure (IOP) using multiplex polymerase chain reaction (PCR) in aqueous humor samples.

MATERIALS AND METHODS

This was a retrospective, observational study of immunocompetent patients living in South Korea. Eligible subjects had typical corneal endotheliitis with an IOP≥21 mm Hg or required antiglaucoma medication. Multiplex PCR was performed using aqueous humor samples obtained at first visit to detect the DNA of 6 herpesviruses.

RESULTS

Forty-two eyes from 42 patients with >6 months' follow-up were analyzed. Of these, 16 were herpesvirus-positive: 3 herpes simplex virus 1, 3 varicella-zoster virus, 9 cytomegalovirus, and 1 Epstein-Barr virus. Eyes with coin-shaped or fine keratic precipitates (kps), high IOP, and a low baseline endothelial cell count were more likely to show a positive result on multiplex PCR. Univariate analysis showed that male sex (P=0.014), a previous history of uveitic glaucoma (P=0.048), and the presence of fine kps (P=0.031) were significantly associated with a positive PCR result. On multivariate analysis, male sex (P=0.010) and a previous history of uveitic glaucoma (P=0.031) showed a significant positive association.

CONCLUSIONS

Cytomegalovirus was the most commonly detected herpesvirus in patients with corneal endotheliitis and high IOP. A positive PCR result was seen more frequently in male individuals and patients with fine kps or a history of uveitic glaucoma.

A Review of Corneal Endotheliitis and Endotheliopathy: Differential Diagnosis, Evaluation, and Treatment

The corneal endothelium plays an integral role in regulating corneal hydration and clarity. Endotheliitis, defined as inflammation of the corneal endothelium, may disrupt endothelial function and cause subsequent visual changes. Corneal endotheliitis is characterized by corneal edema, the presence of keratic precipitates, anterior chamber inflammation, and occasionally limbal injection, neovascularization, and co-existing or superimposed uveitis. The disorder is classified into four subgroups: linear, sectoral, disciform, and diffuse. Its etiology is extensive and, although commonly viral, may be medication-related, procedural, fungal, zoological, environmental, or systemic. Not all cases of endothelial dysfunction leading to corneal edema are inflammatory in nature. Therefore, it is imperative that practitioners consider a broad differential for patients presenting with possible endotheliitis, as well as familiarize themselves with appropriate diagnostic and therapeutic modalities.

Ocular involvement associated with varicella in adults

BACKGROUND

Varicella is a common infectious disease primarily of childhood that is usually benign and self-limited. It is, however, increasingly seen in adults who are at a higher risk of severe infection. Ocular complications of varicella are relatively uncommon and have been rarely described in adults. We describe herein five adults who developed ocular involvement in association with primary varicella-zoster virus infection.

FINDINGS

Ocular manifestations included acute anterior uveitis in four eyes, with associated stromal keratitis in one of them, epithelial ulcerative keratitis in the two eyes of one patient, and acute retinal necrosis in one eye. One patient with acute anterior uveitis was treated with topical steroids and cycloplegic agents. The four other patients received topical or systemic antiviral drugs, with subsequent resolution of acute ocular inflammatory disease.

CONCLUSIONS

The spectrum of chickenpox-associated ocular complications in adults is wide. Early diagnosis and appropriate management are mandatory to improve visual outcome.