Managing Herpes Simplex Epithelial Keratitis
BY WILLIAM L. MILLER, OD, MS, PHD, FAAO
The ocular surface manifestations of the herpes simplex virus (HSV) can take on many forms, and in its early stages it can often be confused with other corneal conditions. Estimates place the frequency of ocular HSV at 24,000 new cases and 34,000 recurring cases per year (Liesegang et al, 1989). Some suggest that the rate of ocular HSV may be increasing due to delays in exposure to HSV-1 (Farooq and Shukla, 2012).
Signs and Symptoms
Patients typically present with corneal lesions that may start as oddly configured epithelial lesions. Ultimately, they will develop into the classic dendritic ulceration with arborization and terminal end bulbs as viewed with fluorescein and rose bengal dyes. This key finding can help you distinguish the corneal ulcers from pseudodendrites. In some cases, these lesions can appear as geographic irregularities or ulcerations. Blisters around the mouth, nose, and eyelids may also occur.
Many patients will experience eye irritation or pain along with an inflamed eye preceding the corneal manifestations. Prior episodes will also produce a corneal hypoesthesia and corneal scarring.
The evidence-based medicine approach provided by the Herpetic Eye Disease Studies (Barron et al, 1994; The Herpetic Eye Disease Study Group, 1997) have guided practitioners on ocular HSV management since their publication. Standard treatment involves antiviral medications for epithelial HSV. Controversy exists over whether oral antivirals should be used for acute episodes. Some corneal specialists opt for an oral rather than a topical antiviral, while some would combine the two. Oral antivirals are considered for the epithelial form of the disease because they reduce the viral load in the ciliary ganglion and associated nerves (Collum et al, 1989; Young et al, 2010). Other factors that may predicate the use of oral antiviral medications alone include the possible toxicity caused by topical antiviral drops, cost considerations, and possible compliance issues.
Topical treatment for acute or recurrent forms of epithelial HSV has traditionally included the use of Viroptic (trifluridine, Pfizer). The drug helps prevent viral replication by blocking DNA transcription. Viroptic can cause corneal toxicity, which will appear as increased bulbar hyperemia, infiltrates, irritation, and pan-corneal staining. For this reason, the medication is not recommended for use beyond 21 days, although toxicity may occur in as little as one week. A more recently approved (2009) topical antiviral indicated for use in acute herpetic keratitis is Zirgan (ganciclovir gel 0.15%, Bausch + Lomb) (Sahin and Hamrah, 2012; Croxtall, 2011). The medication has shown lower levels of toxicity when compared to Viroptic. Adverse reactions that may occur with Zirgan include eye irritation, blurred vision, punctate keratitis, and conjunctival hyperemia.
If you choose to accompany your treatment with an oral antiviral, Valtrex 500mg (valacyclovir, GlaxoSmithKline) can be prescribed. The use of topical steroids is reserved for complete resolution of the dendritic ulcerations in conjunction with cases of disciform and stromal involvement.
Co-management with a corneal specialist is encouraged and may be warranted in cases of recurrent disease and/or deep stromal involvement. CLS
For references, please visit www.clspectrum.com/references.asp and click on document #222.
Dr. Miller is an associate professor and chair of the Clinical Sciences Department at the University of Houston College of Optometry. He is a consultant or advisor to Alcon and Vistakon and has received research funding from Alcon and CooperVision, and lecture or authorship honoraria from Alcon and B+L. You can reach him at firstname.lastname@example.org.