Avoiding vision loss from infectious keratitis after LVC

Infectious keratitis is not a common complication after laser vision correction (LVC), but it is important because it can be devastating, said Deepinder K. Dhaliwal, MD.

“Half of patients who develop infectious keratitis after LVC will have moderate-to-severe reduction in visual acuity,” said Dr. Dhaliwal, professor of ophthalmology, University of Pittsburgh School of Medicine, Pittsburgh.

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“Therefore, it is better to prevent infectious keratitis than to have to treat it,” Dr. Dhaliwal said. “If it occurs, prompt recognition and aggressive treatment are critical, and then patients may have a good result.”

Infectious keratitis after LVC can occur early or late after the primary surgery, a flap lift, an enhancement, or even following late trauma, as illustrated by a case Dr. Dhaliwal described involving a patient who was hit in the eye with a banana 10 years postLASIK.

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The pathogen may come from the patient, residing on the conjunctiva, lid margins/lashes, or transferred from the fingers. Alternatively, a host of operative factors can be the source, including surgical instruments, microkeratomes, sponges, or nonsterile water.

Optimization of the ocular surface with treatment of existing conditions, e.g., dry eye, blepharitis, rosacea, is a critical prevention strategy. The agents used depend on the patient’s diagnosis and may include hypochlorous acid 0.01%, oral nutraceuticals, topical anti-inflammatory medications, lid hygiene, and tea tree oil lid scrubs.

Placement of punctal plugs is reserved until after inflammation is controlled, and Dr. Dhaliwal reminded surgeons to ask patients about a history of herpes simplex virus infection, recognizing the risk for reactivation.

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Perioperatively, her infection prophylaxis regimen incorporates treatment with a fourth generation fluoroquinolone, antisepsis with 10% povidone-iodine applied to the lids and lashes, and draping to isolate the lid margin.

“I am super compulsive about draping, and I do it myself, trying to be certain that the meibomian glands are all covered,” Dr. Dhaliwal said.

Two separate sets of instruments are used, one for each eye to avoid cross contamination, and all fluids used are sterile.

“Never use nonsterile water in the surgical environment,” she cautioned, citing an article in Morbidity and Mortality Weekly Report describing a cluster of postLASIK mycobacterial infections occurring in 2015 that were traced to a humidifier used in the LASIK clinic.

Follow-up

After surgery, the fourth-generation fluoroquinolone is continued with instillation every 2 hours for the first day after surgery and then four times daily for 1 week.

Dr. Dhaliwal said that the follow-up examination is also something that she never delegates to anyone else. Distinguishing between infection and diffuse lamellar keratitis (DLK) is key.

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“I look very carefully for inflammation and follow patients with suspected DLK very closely,” she said. “If there is an atypical pattern with any focal consolidation under the flap, think infection until it is proven otherwise.”

Patients are also counseled about the signs and symptoms of infectious keratitis so that they will seek prompt attention.

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Recognition of infectious keratitis requires remembering that it can be an acute or delayed complication and that the clinical appearance may be atypical because of interface spread and corticosteroid use.

The causative pathogens tend to vary by time of infection onset. After LASIK, acute infections are most often caused by Gram-positive bacteria whereas atypical organisms, nontuberculous mycobacteria or fungi, are more common causes for later onset infections (>2 weeks postoperatively. Infectious keratitis after PRK typically occurs early and is caused by Gram-positive bacteria, Dr. Dhalilwal said.

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However, these are not steadfast rules. Therefore, it is critical to obtain scrapings and material for culture, and the specimens should come from under the flap in postLASIK eyes.

“If you try to culture from the surface, there will not be adequate yield of organisms,” Dr. Dhaliwal cautioned.

Management

Management involves lifting the flap to debulk the infiltrate followed by irrigation using agents targeting the likely pathogens, i.e., vancomycin for acute infections and amikacin for late infections. If the flap is necrotic or nonadherent, it should be excised to enable penetration of the antimicrobial agent.

Topical treatment is continued with fortified cefazolin or vancomycin plus a fluoroquinolone for acute infections and amikacin plus a fluoroquinolone for delayed infections.

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The regimen also includes oral doxycycline to inhibit collagenase, and Dr. Dhaliwal emphasized the importance of discontinuing corticosteroids and modifying treatment according to findings from the microbiology laboratory.

“Let the body fight the infection, let the antimicrobials do their job, and tailor the treatment based on the results of culture and scraping,” she said.

Dr. Dhaliwal is a consultant for Bausch + Lomb and Novabay. She conducts research for and is a speaker for Abbott, Avedro, Imprimis Pharmaceuticals, Oasis, Ocular Systems, Ocular Therapeutix, and STAAR Surgical.