If HSV keratitis occurs after ocular surgery, treatment depends on whether the infection is caused by the live virus, an immune-mediated reaction, or a metaherpetic process, Dr. Yeu said.
She recommended maintaining enough topical steroids to facilitate recovery from the surgery, but to mitigate topical steroids in the setting of epithelial keratitis.
The active live virus can cause dendrites or geographic ulcers of the epithelium, necrotizing keratitis in the stroma, and keratouveitis in the anterior chamber. Immune-mediated HSV keratitis includes non-necrotizing stromal keratitis, disciform or linear endotheliitis, and possibly keratouveitis, she said.
Non-necrotizing HSV stromal keratitis is associated with the highest and most severe ocular morbidity, Dr. Yeu said, and can include stromal edema, vascularization or lipid deposition with the epithelium intact, and an antibody-complement cascade against retrained viral antigens in the stroma.
All endotheliitis should be treated with aggressive topical steroids, she said.
The disciform is the most common form. It is immune-mediated and can be recognized by its disc-shaped area of edema and keratic precipitates, Dr. Yeu added.
The diffuse form, which is also immune-mediated, is characterized by dense retrocorneal plaque. Linear endotheliitis, on the other hand, may be a sign of a live virus.
A metaherpetic keratitis process, such as a neurotrophic ulcer or drug toxicity, should be considered where the cornea fails to re-epithelialize after 14 to 21 days of treatment, Dr. Yeu said.
“Metaherpetic means something transitional,” she explained. “You know something else going on.
“It could be neurotrophic,” she said. “It could be that the nerves are so damaged from prior HSV infections that the cornea itself doesn’t sense that something is wrong so it doesn’t trigger the processes in order to heal that wound. Or it could be treatments that are too toxic for it.”
Trifluridine, which was considered a treatment of choice prior to topical gancyclovir, “is extremely toxic and was a common culprit for a poorly healing corneal epithelium,” Dr. Yeu said. A secondary infection could be another reason for metaherpetic keratitis.
Signs of neurotrophic keratopathy include confinement within the interpalpebral fissure; epithelization that has been delayed for more than 2 to 3 weeks; poor sensation; and oval, rolled edges with smooth borders.