October 2016

 

REFRACTIVE

 

Infection following femtosecond AK


by Maxine Lipner EyeWorld Senior Contributing Writer

 
   
MRSA infection
MRSA infection within femtosecond laser astigmatic keratotomy incision Source: Timothy Chou, MD

A case of early- and late- onset infectious keratitis

It’s the kind of thing a physician wouldn’t expect: A patient who has undergone uneventful femtosecond laser-assisted cataract surgery with two laser-created astigmatic keratotomies (AK) is plagued by a couple of infections, the second occurring 5 months after surgery. That’s what Timothy Chou, MD, assistant clinical professor of ophthalmology, Stony Brook University, Stony Brook, New York, found himself facing while treating a referral patient.

Such infections seem unheard of with femtosecond-assisted AK. “To my knowledge, the case that we reported is the first case,” Dr. Chou said. “I looked at the literature and did not see any other reports since our report of infection after femto-enabled AK.” This report was published in the Journal of Cataract & Refractive Surgery.1

Initial presentation

The referring surgeon explained to Dr. Chou that the 79-year-old patient’s eye was more inflamed than usual after the surgery and at 1 week postop, but there was no sign of corneal infection. “Nevertheless, they stopped the postoperative antibiotic, which in this particular case was besifloxacin, after 1 week,” he said. “The patient did continue routine postoperative steroids, however.” Despite this, she became progressively more inflamed and at 2.5–3 weeks postop, she began to develop an infiltrate in the superotemporal AK incision. “At that point, the patient was referred to our university corneal service for further management,” Dr. Chou said, adding that she had a very obvious intensive corneal infiltrate in the AK incision and surrounding the incision, as well as a significant hypopyon. Practitioners noted that there was no infection within the corneal tunnel and paracentesis. In addition, there was no evidence of endophthalmitis, Dr. Chou said. After undergoing a battery of smears and cultures, the patient was placed on fortified vancomycin and fortified tobramycin eye drops, Dr. Chou reported. Since her IOPs were also high, she was placed on dorzolamide/timolol twice per day. “We started her on oral doxycycline because she had underlying blepharitis,” he said. “We also gave her bacitracin ointment to the eyelids and instructions for eyelid hygiene.” Cultures were positive for methicillin-resistant Staphylococcus aureus (MRSA). While the infection ultimately cleared, it took some time. This did not surprise Dr. Chou because in his experience MRSA corneal infections often resolve more slowly. “In this patient’s case, after 5 weeks of treatment, we felt that her infection had cleared,” he said. However, 5 months after cataract surgery, the patient developed a new infiltrate in the same AK incision. This was treated in a similar fashion as an infectious keratitis. “That one cleared fairly quickly, and that was the last infection she had,” he said. “Her final best corrected visual acuity at 6 months was 20/30 in the operative eye.” Dr. Chou has several theories on why the two infections occurred. First, he pointed out that anything that breaks the surface of the epithelium can provide a portal of entry for infection. In this particular case, the patient was a MRSA carrier. As a result, the germs may have been more virulent than run-of-the-mill ocular surface flora, he explained. Dr. Chou thinks there was more going on. “There might have been some mechanical weakness of the keratotomy incision that allowed for invasion of microorganisms into the substance of the cornea.” There have been cases of delayed infectious keratitis after mechanical keratotomy, believed to be facilitated by poor healing of incisions. “We postulated in this case, and this has been reported in the literature, that in cases where keratotomy incisions do not heal well, rather than the stroma healing with scarring, it heals with an epithelial plug that grows into the wound,” he said. “If that plug is lost, there will be a defect where the plug was, which might allow microorganisms to invade.” Yet another factor may have been the medications that the patient was taking, Dr. Chou pointed out. He mentioned a 2013 ASCRS report that detailed how newer medications with an advanced vehicle designed to decrease toxicity and improve lubrication and comfort might inhibit wound healing. “She was taking besifloxacin, nepafenac, and difluprednate,” he said, adding that ASCRS found that all three of these could inhibit wound healing in laser refractive patients. Intrigued by the fact that she was on such medications, investigators considered whether this could have been a contributory factor, where her AK incisions may not have healed as readily as in someone who was on different medications.

Clinical message

From a clinical perspective, the case drives home a couple of points, Dr. Chou said. For one, it clarifies the importance of blepharitis awareness. “In this patient’s case, she had advanced blepharitis that was not well-controlled at the time she presented to us,” he said. “The referring surgeons had not identified that or put her on any blepharitis treatment beforehand.” Dr. Chou thinks it is important for surgeons to carefully identify patients who may be at higher risk of not only MRSA but also common bacteria that could be on the ocular surface due to blepharitis and to treat them prior to surgery.

Secondly, the case reveals the importance of proper patient preparation from the start. “In this center, they did not prep the patient during the laser-assisted portion of the cataract surgery,” Dr. Chou said. “Once they did the laser cuts, they moved the patient over to the operating area and at that point prepped the patient.” Investigators here don’t think this is sufficient. “We have suggested that since these laser cuts go right through the epithelium, the patient should be prepped prior to the laser portion of the laser-assisted cataract surgery,” Dr. Chou said. While this is just one case, another possibility for avoiding infection may be to use intrastromal keratotomies instead since the relaxing incisions can be made with the cornea stroma itself without breaking through the epithelium, he pointed out.

Dr. Chou stressed that while these infections are uncommon, they should remain on the radar. “I think that laser-assisted keratotomies and laser-assisted cataract surgery has been shown to be generally safe, but MRSA and other resistant infections are a growing problem that has been recognized and identified,” he said. “Surgeons should be careful to identify patients at risk and treat accordingly prior to cataract surgery.”

Reference

1. Chou TY, et al. Early-onset methicillin-resistant Staphylococcus aureus keratitis and late-onset infectious keratitis in astigmatic keratotomy incision following femtosecond laser-assisted cataract surgery. J Cataract Refract Surg. 2015;41:1772–7.

Editors’ note: Dr. Chou has no financial interests related to his comments.

Contact information

Chou: Timothy.Chou@stonybrookmedicine.edu

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Femto in cataract surgery: The state of the technology by Liz Hillman EyeWorld Staff Writer

Large study to compare conventional phaco to femtosecond laser surgery by Erin L. Boyle EyeWorld Senior Staff Writer

Dissonance in a femtosecond by J.C. Noreika, MD, MBA

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An update on billing policy for femtosecond laser use by Ellen Stodola EyeWorld Staff Writer

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