Diagnosing and Treating Herpes Simplex Keratitis
BY WILLIAM MILLER, OD, PHD, FAAO
Herpes simplex keratitis (HSK) is an infrequent corneal infection with potential for dire visual consequences. It is the leading cause of infectious corneal blindness in many countries, including the United States. Other ocular structures affected include the conjunctiva (conjunctivitis), adnexa (eyelid vesicles) and anterior chamber (iritis). Dilemmas frequently occur in differentially diagnosing HSK from entities which it can masquerade, including herpes zoster ophthalmicus and fungal and acanthamoebic keratitis. In-vivo confocal microscopy has provided a tool to differentiate acanthamoebic and fungal keratitis from HSK, but its use has not become widespread in clinical practice, instead remaining in research areas and specialized corneal disease centers.
HSK symptoms include recurrent bouts of red, painful eyes. Pain is typically mild to moderate and rarely severe. Biomicroscopy with staining reveals dendritic ulcerations highlighted centrally and at the ulcer's edge with fluorescein while exhibiting a stained ulcerative margin with rose bengal.
Rose bengal administration will decrease the viral load, which is an issue when culturing is indicated such as in atypical presentations or cases unresponsive to antiviral therapy. Skin lesions and anterior uveitic responses may be present depending on severity and previous episodes.
Triggers to secondary HSK episodes include stress, ultraviolet light, trauma and possibly prosta-glandin antiglaucoma medications and LASIK. You can modify or avoid the last two triggers for patients with a history of HSK.
Figure 1. Stromal scarring from recurrent
Typically, use topical antivirals during active epithelial disease and steroids in cases of stromal herpes. In some cases of stromal herpes with epithelial involvement, use a topical antiviral concomitantly with topical steroids.
Use Viroptic (trifluridine 1%, Monarch) nine times per day for no longer than 21 days. Vidarabine 3% ointment may also be indicated for bedtime use. Steroid intervention for immune stromal or combined epithelial-stromal disease may include prednisolone acetate 0.125% (for mild cases) or 1%.
The NEI-funded Herpetic Eye Disease Study (HEDS I and HEDS II) has over the last several years revealed one of the most promising findings for patients who often succumb to recurrent bouts of HSK. HEDS I showed the importance of prednisolone acetate in resolving active stromal disease when compared with a placebo. This same study failed to show any benefit to short-term use of oral acyclovir in cases of active stromal disease when used in conjunction with a topical antiviral and steroid. HEDS II illuminated the importance of long- term oral acyclovir use for the prevention of recurrent episodes of stromal keratitis. A prophylactic administration of oral acyclovir 400 mg bid demonstrated a 41 percent reduction in any future herpetic eye disease incidents. In addition, a 50 percent reduction in recurrent episodes was evident in patients who had experienced stromal herpetic eye disease in the previous year.
Dr. Miller is on faculty at the University of Houston College of Optometry. He is a member of the American Optometric Association and serves on its Journal Review Board. He can be reached at firstname.lastname@example.org.