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Be on the lookout for infectious keratitis after refractive surgery
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Infectious keratitis after refractive surgery is of great concern despite few cases of infectious keratitis following photorefractive keratectomy (PRK) being reported and the absence of any reported cases following laser in situ keratomileusis (LASIK). Infectious keratitis after refractive surgery is handled much like infectious keratitis in any patient. While few cases occur, specific guidelines should be followed in managing this potentially blinding condition.
One of the first cases of ulcerative keratitis in a PRK patient was in the Visx U.S. clinical trials. Postoperatively, the patient's eye was patched. All other reported cases have occurred in patients who have utilized a therapeutic bandage contact lens following surgery.
Fungal keratitis
--- Blepharitis with phlyctenulosis. Blepharitis must be treated prior to refractive surgery.
A more significant report by Faschinger and colleagues of four patients who developed fungal keratitis with Aspergillus appears in the Northern European Journal of Implant and Refractive Surgery (Faschinger C, Grasl M, Ganser K. Infectious corneal ulceration and endophthalmitis after PRK with use of disposal contact lenses. Eur J Implant Ref Surgery. 7:1-8, 1995).
Other than these cases of fungal keratitis, culture-positive results are most commonly seen with staphylococcal bacteria. For this reason, it is imperative that chronic lid margin conditions such as blepharitis or meibomianitis be treated prior to refractive surgery.
Prior to surgery, patients can perform lid hygiene with warm compresses and apply an antistaphylococcal antibiotic, such as bacitracin ointment, to reduce the bacterial population.
Ulcerative keratitis and nonhealing epithelial defects can also be caused by an undiagnosed systemic autoimmune condition or a collagen vascular disease. Conditions such as lupus, arthritis and uncontrolled diabetes are contraindicated for PRK or LASIK as they all increase the risk of infectious keratitis by increasing corneal epithelialization time.
Discontinue contact lenses
--- Peripheral corneal melt in a patient with severe arthritis. Arthritis is contraindicated for either PRK or LASIK.
At the first sign of infiltration contact lenses should be discontinued, and if the infiltrate is suspicious, large or central, cultures of the cornea and contact lenses should be performed. At our center, cultures are performed on three media and two smears. The media are blood agar, chocolate agar and Sabouraud dextrose agar.
Cultures are also plated for Giemsa's staining. If fungal keratitis is suspected, thioglycollate broth is also indicated as a culture medium.
Sterile infiltrates are open, peripheral and multiple, and the overlying epithelium is intact. They are simply an immune response to either hypoxia or some offending agent, causing the immune system to produce greater amounts of leukotrienes.
It is suspected that the combination of a bandage contact lens and nonsteroidal anti-inflammatory drops (as are used post-PRK) contribute to sterile infiltrate formation. The theory postulates that a nonsteroidal anti-inflammatory drug's mechanism of action is to suppress prostaglandin formation by inhibiting the enzyme cyclooxygenase (hence, decrease pain sensation). This, however, may lead to greater amounts of leukotriene formation.
Antibiotic/steroid therapy, for example, tobramycin/dexamethasone (TobraDex, Alcon), is an effective treatment for sterile corneal infiltrates.
Suspicious infiltrates
At the first sign of infiltration, such as this infectious keratitis, contact lens wear should be discontinued.
One must be careful not to identify an infectious infiltrate as sterile. The use of steroids in an infiltrate may hasten the corneal damage. Do not rule out infectious causes in a suspicious infiltrate, and if an infectious cause is indicated one should culture to confirm the diagnosis.
The treatment of bacterial keratitis is the same for postoperative patients and contact lens patients. Following culturing, the patient is started on fluoroquinolone therapy every 15 minutes for 2 to 6 hours, then hourly thereafter. Treatment of sight-threatening ulcers should also include the use of fortified cefazolin (33 to 50 mg/cc). Ulcers produced by methacillin-resistant Staphylococcus may also require the use of fortified topical vancomycin (20 to 50 mg/cc). I alternate the fortified antibiotic every 30 minutes with the fluoroquinolone.
As corneal healing occurs, the dose of antibiotic may be reduced accordingly. Occasionally, topical steroids may be utilized to reduce local inflammation and corneal scarring; however, great care must be exercised in choosing this treatment option. Topical steroids must not be used in the acute infectious phase of the disease.
Anterior chamber inflammation and ciliary spasm should be treated initially with cycloplegic agents - scopolamine hydrobromide 0.25% (Isopto Hyoscine, Alcon) once or twice daily or homatropine 5% three times daily are excellent choices when utilized in the initial treatment phase.
Following resolution of the ulcerative condition, the patient will usually have a residual opacity and irregular astigmatism.
Treating opacity
Treatments for the opacity include excimer laser phototherapeutic keratectomy (PTK) or corneal transplantation. PTK will also assist in reducing the residual irregular astigmatism. Other treatments for the residual irregular astigmatism include a rigid contact lens. These options are not indicated until 6 to 12 months after resolution of the ulcerative disease.
There has never been a case of infectious keratitis following LASIK reported in the literature; however, there is certainly potential for contamination to give rise to intrastromal ulceration. Therefore, LASIK requires perioperative antibiotics, meticulous surgical asepsis and careful irrigation of debris from the stromal bed and flap. Treatment for infectious ulcer following LASIK would be very similar to that of the PRK ulcerative keratitis described above.
Fluoroquinolone recommended
A fluoroquinolone would be the recommended topical medication due to its corneal penetrating abilities. Because the treatment area following LASIK is 160 µm deep into the cornea, a topical antibiotic with corneal penetration, such as a fluoroquinolone, is recommended.
The medication should be used every 30 minutes while awake and approximately every 1 to 2 hours at night, depending on the severity of the ulceration. A loading dose of one drop every 15 minutes for the first hour is also recommended.
With LASIK, if no improvement is noted, after a day or two of this therapeutic regimen the patient may be sent to surgery, have the flap lifted, have the debris irrigated using an antibiotic solution, have cultures taken and be treated as described earlier. Again, this is theoretical, as no cases have been reported.
No-win situation
Although extremely rare, infectious ulcers can be extremely devastating following refractive surgery. Therefore, the comanaging doctor must take great care in deciphering sterile infiltrates vs. infectious ulceration. Proper documentation, which includes culturing, drug selection and frequent monitoring, are central to the management of infectious keratitis. Any central ulcer or one that threatens the patient's vision should be comanaged with the corneal surgeon.
For Your Information:
- Paul M. Karpecki, OD, is director of research for the Novamed/Hunkeler Eye Study Center and the clinical director of cornea and refractive surgery for the Hunkeler Eye Center. He is also the residency director of the Corneal and Refractive Surgery Residency fellowship program affiliated with the Pennsylvania College of Optometry and a faculty member of the Kansas University Department of Ophthalmology, where he heads the refractive surgery clinic program for residents. He may be contacted at 4321 Washington, Suite 6000, Kansas City, MO 64111; (816) 931-4733; fax: (816) 931-9498; e-mail: pkarpecki@novamed.com. Dr. Karpecki has no direct financial interest in any of the products mentioned in the article, nor is he a paid consultant for any company mentioned.
- Pharmacology and the Eye is edited by Bruce E. Onofrey, OD, RPh, who is responsible for primary care eye services at Lovelace Medical Center, Montgomery Eye Clinic in Albuquerque. He lectures on the management of ocular disease and the use of pharmaceutical agents, and is a charter member of the Editorial Advisory Board of Primary Care Optometry News. He may be contacted at 9101 Montgomery Blvd. NE, Albuquerque, NM 87111; (505) 275-4226; fax: (505) 275-4023. Dr. Onofrey has no direct financil interest in any of the products mentioned in this article, nor is he a paid consultant for any company mentioned.