Infections following any eye surgery can be devastating, but this is especially the case for refractive surgeries due to the elective nature of the procedures. Before the procedure, the patient’s eyes were otherwise normal, and an infection can have a lasting and severe impact. Thus, it is important to practice meticulous infection control from the preoperative period through the postoperative period. This article discusses the pathology of infection and some of the most efficient methods for exercising that control.
Infection incidence and symptoms
The incidence of infection following LASIK varies from 0.2% to 1.2%. Numerous case reports of infection have been published, and among the 90 reports 5% were bilateral infection. Symptoms of infection include redness, decreased vision, photophobia and, most commonly, pain. These patients rarely experience foreign body sensation or discharge.
Typically, a corneal infiltrate is present, and an anterior chamber reaction is seen in at least 50% of patients; epithelial defects can also be seen. Patients can also have flap separation, epithelial ingrowth or flap melting.1
There are two distinct timings of postoperative infection: early onset, typically within the first week after LASIK; and late onset, which can begin after 10 days up to 3 months following surgery. Early-onset infections are almost always gram-positive bacteria, whereas late onset infections tend to be more opportunistic organisms such as atypical mycobacteria, fungi and nocardia.
Risk factors for infection
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| || Patient risk factors include blepharitis and meibomian gland dysfunction, dysfunctional tear state, herpes simplex keratitis and collagen vascular disease. |
—Helen K. Wu, MD
There are risk factors for infection associated with both the patient and the procedure. Patient risk factors include blepharitis and meibomian gland dysfunction, dysfunctional tear state, herpes simplex keratitis and collagen vascular disease. Patients with HIV may also be at greater risk of infection. Procedural risk factors include the lack of aseptic technique, the use of topical steroids, abuse of topical anesthetic or an epithelial defect that occurs during the procedure, failure to administer postoperative antibiotics and reoperation (Table 1).
After the procedure is completed, there are long-term risk factors as well. Trauma to the eye is one of these, as are epithelial instability due to exposure to contaminated fluids such as drops or swimming pool water and contact lenses with an over- or under-correction. Reoperation also raises the risk of infection, as does long-term use of any topical medication.
Preoperative infection prophylaxis
The three phases of perioperative infection control include preoperative measures, local intraoperative control-prepping and draping and finally postoperative prophylaxis. One of the most important aspects to preoperative control is to treat LASIK as an ophthalmic surgical procedure rather than a nonsurgical treatment. Thus, staff should be instructed in the principles of sterile operative technique; brief hand scrubs prior to each procedure should be encouraged.
Eye make-up is one of the biggest potential sources of dangerous bacteria in both male and female patients; patients should be instructed to avoid wearing make-up before the procedure. Even still, most make-up removers will not eliminate 100% of the make-up, so using an alcohol swab to remove any residual amounts before prepping and draping the patient is recommended. Patients should also suspend contact lens use at least 72 hours before the procedure.
| ||An ideal preoperative antibiotic used for prophylaxis would have appropriate microbial coverage and good tissue penetration, and should be administered, at most, twice a day. |
—Helen K. Wu, MD
Applying povidone-iodine on the lashes and lids before surgery is crucial, and blepharitis should be treated thoroughly. This includes eye scrubs, warm compresses, nutritional supplements, topical cyclosporine and antibiotics. An ideal preoperative antibiotic used for prophylaxis would have appropriate microbial coverage and good tissue penetration, and should be administered, at most, twice a day. It should also be nontoxic and affordable to the patient.
The preferred antibiotic agents are the fourth-generation fluoroquinolones such as gatifloxacin and moxifloxacin, and recent pharmacokinetic studies in rabbits have indicated that an azithromycin formulation results in high concentrations in the cornea and could further aid in infection prevention.
If symptoms of an infection are seen either in the early or late postoperative periods, a number of steps should be taken. The flap is a barrier to culturing for infection as well as penetration of antibiotics, so raising the flap is the first step. First this is done to scrape, irrigate and culture for infection; it is important to use the appropriate culture media, including blood agar, chocolate agar, Sabouraud’s agar for fungus and thioglycolate broth. If a late-onset mycobacterial infection is suspected, the Lowenstein-Jensen media is appropriate. The correct smears are also important. These include Gram, Giemsa, calcofluor and AFB smears. In difficult cases, obtain a corneal biopsy or PCR, and access to confocal microscopy can aid in diagnosis.
At the same time that scraping and culturing is performed, irrigation with appropriate antibiotics can also be performed. If an early-onset gram-positive infection is suspected, vancomycin can be effective. For later onset infections, irrigation with amikacin can be used.
Initial antibiotic treatments should be tailored to the smear results when possible (Table 2). Fortified tobramycin and cefazolin or vancomycin can be used, and raising the dose of moxifloxacin or gatifloxacin is another possibility (or switching to the latter two if they were not used initially). With late-onset infection, if mycobacteria are responsible, then amikacin plus clarithromycin or azithromycin can be used. Moxifloxacin and gatifloxacin have some activity against atypical mycobacteria and can be useful for these infections as well. For fungal infections, natamycin and amphotericin B are useful possibilities. With all treatments for infection, careful attention should be paid to the course of infection: if it appears to be improving, the chosen treatment should be continued. With no progress or worsening, treatment should be tailored to culture and sensitivity results.
After an infection has been successfully eliminated, patients often will have irregular astigmatism and scarring that can limit vision. It may be necessary to wait as long as 1 year to treat these problems, as the tissue remodels and vision can become less hazy. Eventually, treatment can include PTK, deep anterior lamellar keratoplasty, rigid gas-permeable contact lenses or penetrating keratoplasty.
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| ||Infections following LASIK are devastating events given the elective nature of the procedures. |
—Helen K. Wu, MD
Infections following LASIK are devastating events given the elective nature of the procedure. Following some fairly simple guidelines, however, can drastically reduce the incidence of infection and can improve treatments when infections do occur.
- Azar DT, Koch D, ed. LASIK: Fundamentals, surgical techniques and complications. Informa Healthcare. 2002.