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Several issues may restimulate the virus in those patients with prior exposure.
Reviewed by Dr David R. Hardten.
Nothing is perfect, and although corneal collagen cross-linking (CXL) to treat keratoconus is safe and stops the progression of disease, infections can occur.
Herpes simplex virus (HSV) keratitis is one possibility, according to Dr David R. Hardten from the Minnesota Eye Consultants in Minnetonka, who suggested that most cases associated with CXL are recurrences.
Dr Hardten addressed the question of what causes HSV keratitis to recur and noted that the traumatic epi (epithelium)-off procedure, use of steroids to reduce haze, and exposure to 30 minutes of ultraviolet light may be the culprits in restimulating the virus in patients with prior exposure. He also explained that with the epi-on procedure, the epithelium is disrupted, which leaves the scene open for an HSV recurrence.
“There are a number of different risk factors that can create that environment in which HSV can flourish,” he said.
Although HSV likely cannot be prevented all the time, a few things can be done that may preclude the development of HSV keratitis.
The first is to examine the patient for scarring that may be present from a previous infection or from keratitis associated with contact lens wear. Other options include asking the patient about a history of HSV and looking for evidence of previous atopic disease by comparing the 2 eyes.
In patients with a history of disease, Dr Hardten pre-treats the eyes with an oral antiviral agent such as valacyclovir. This is administered 3 times daily about 1 week before the planned CXL procedure and then postoperatively in a tapering dosage.
“I still perform CXL in these patients,” he said. He estimates the risk in those with recurrent HSV to be similar to that in patients undergoing PRK and recommends performing the procedure because the benefits outweigh the risks. He proceeds by increasing the maintenance dose of the antiviral agent in those patients who had a previous infection.
The most important thing to watch for, he noted, is a postoperative persistent or enlarging epithelial defect. These are characterized by the presence of geographic ulcers that have a broader base than the typical narrower dendrites one would see with HSV in patients not taking steroids. The risks associated with administering an antiviral agent to these patients are very low, he commented.
Dr Hardten advised physicians to proceed with caution.
“I think that CXL is relatively safe,” he explained. “However, there are some potential complications.”
Dr Hardten added that it is important to look for past evidence of HSV keratitis and ask patients about previous infections.
“Consider increasing the maintenance dose if patients are already receiving maintenance antiviral therapy,” he concluded. “Prophylaxis therapy is appropriate if you are suspicious. Be wary of epithelial defects; if they are slow to close, consider geographic ulcers. If healing does not occur in 4 to 5 days, consider that this may be HSV keratitis.”