Nocardial organisms that belong to the order Actinomycetales are aerobic gram-positive filamentous bacteria existing ubiquitously in the environment.1 Although nocardia species are uncommon as human pathogens, they can cause a variety of skin and pulmonary diseases. Ocular nocardiosis is relatively rare but it may be seen in a spectrum of disease entities such as keratitis2"4, scleritis5, endophthalmitis6, and possibly others. Nocardial keratitis is characterized by its rarity but highly vision-threatening potential because of delayed diagnosis and treatment.7 We report a case ?? Nocardia asteroides keratitis that developed after laser in situ keratomileusis (LASIK) retreatment.
A 39-year-old white male was referred to the Refractive Surgery Section at Alicante Institute of Ophthalmology, Alicante, Spain, in June 1995, for correction of high myopia. The patient had stable high myopia and was unable to wear contact lenses. He rejected glasses because of severe psychological inhibition. The risks of the surgery were fully explained to him in accordance with the Helsinki Declaration. The patient did not have general health problems.
The patient's spectacle-corrected visual acuity was 20/50 in the right eye and 20/100 in the left eye, and the spherical equivalent of the manifest refraction was -12.50 -1.50 X 45° in the right eye and -16.00 -1.50 X 135° in the left eye. Biomicroscopy examination of the anterior segment was normal. Intraocular pressure was 13 mmHg in each eye. Ophthalmoscopy revealed diffuse tesselation and pallor of the fundus, and peripapillary crescent in each eye. Corneal thickness, measured with ultrasonic pachymetry (DGH-500 pachymeter, DGH Technology, Ine, Exton, Penn), was 566 µt& in the right eye and 575 µta in the left eye. Videokeratography was unremarkable and the patient was scheduled for laser in situ keratomileusis (LASIK).
In August 1995, the patient underwent LASIK on the right eye, and 2 weeks later had LASIK on the left eye. The operative technique was described previously.8,9 We used an automated microkeratome (Chiron Automated Corneal Shaper, Chiron Vision, Irvine, Calif), and a 193-nm argon fluoride excimer laser (VISX 20/20 Excimer Laser, VISX Ine, Santa Clara, Calif). A hinged corneal flap technique without sutures and a triple ablation profile (5 mm/5.5 mm/6 mm) were used. The eyes were not occluded after surgery. Antibiotic (tobramycin 0.3%, Tobrex, Alcon Iberhis SA., Alcobendas, Madrid, Spain) and corticosteroid (fluorometholone 0.10%, FML, Allergan S.A., Tres Cantos, Madrid, Spain) eye drops were instilled three times a day for the first 10 days.
Figure 1 : Slit-lamp photograph shows interface central nodules 6 days after LASIK retreatment.
Six months after surgery, the patient's uncorrected visual acuity was 20/65 in both eyes, and spectaclecorrected visual acuity was 20/40 in the right eye and 20/50 in the left. The postoperative spherical equivalent of the manifest refraction was -2.50 -0.50 X 80° in the right eye and +0.50 -0.75 X 90° in the left eye. Slit-lamp microscope examination revealed clear corneas in both eyes; an incomplete gray line at the edge of the flap was noticed in both eyes. Postoperative corneal thickness was 460 µta in the right eye and 415 µ?a. in the left eye.
In February 1996, the patient underwent LASIK retreatment on his right eye. The flap was lifted and the stromal bed reablated. Preoperatively, the patient was taken to the slit-lamp and the edge of the flap was marked with gentian violet at 1 to 2 o'clock on the temporal side. The procedure was performed under topical anesthesia with 0.4% oxibuprocaine, one drop every 10 minutes for half an hour before surgery. The cornea was marked with three pararadial gentian violet lines. A small area of epithelium was debrided using a blunt spanila. A flat spatula was inserted along the corneal flap edge, which had been marked at the slit-lamp. Once the flap interface was identified, the spatula was passed along the flap edge circumferentially, and the interface was dissected. The hinged flap was lifted using the spatula, and placed against the nasal sclera. The excimer laser ablation was performed on the stromal bed using a 6 mm zone. After ablation, the flap was replaced in its original position, and the interface was irrigated copiously with balanced salt solution using a 23G cannula for removing debris and residual epithelial cells. The flap was then centered for proper alignment according to the pararadial marks, and the keratectomy incision was dried with surgical spears. After approximately 3 minutes, the flap was checked for adhesion, until adequate adhesion was assured. The postoperative regimen was identical to that following the primary LASIK procedure. A bandage contact lens was not used. Six hours after surgery, slit-lamp microscope examination revealed a clear cornea, and the flap was well positioned.
Six days after retreatment, the patient complained of photophobia, blurring,and ghost images in the right eye. Slit-lamp examination revealed ciliary injection, and two well-defined whitish nodules surrounded by stromal infiltrate in the central cornea (Fig 1). The nodules were in contact, and were located in the corneal interface. One nodule had a small overlying epithelial defect that stained with fluorescein. The anterior chamber reaction was mild. The posterior segment was normal. This was thought to represent infectious keratitis. The immediate management involved lifting the corneal flap and scraping the corneal stroma in the affected area with a spatula. The stromal bed was irrigated with 0.3% tobramycin and 0.3% ciprofloxacin (Tobrex and Oftacilox, respectively, Alcon Iberhis S.A., Alcobendas, Madrid, Spain), and the flap was replaced in its original position. The exudate and tissue from the lesion were placed on a microscope slide for Gram staining, and also on blood, chocolate, MacConkey and Tayer-Martin agar and Brain-Heart infusion for bacterial culture, and Sabaroud's medium for fungal culture.
The smears revealed a gram-positive branching bacteria (Fig 2), and hourly topical fortified tobramycin (15 mg/ml) and vancomycin (25 mg/ml) were started on the same day. Cultures were subsequently (after 48 h of incubation) positive for Nocardia asteroides. The organism was identified as N. asteroides based on its morphology, stain features, inability to hydrolyze casein, tyrosine, xanthine, gelatin, and urea, and ability to reduce nitrate to nitrite. Topical antibiotics were changed empirically2·4·7 to sulfacetamide 20% (Colircusi Sulfacetamida 20%, Laboratorios Cusí S.A., Barcelona, Spain), and trimethoprim 0.1% (Oftalmotrim, Laboratorios Cusí SA., Barcelona, Spain), which were started at 1-hour intervals around the clock. The patient was also given two trimethoprim-sulfamethoxazole tablets (160/800 mg) twice daily (Septrin, Gayoso- Wellcome S.A, Alcalá de Henares, Madrid, Spain). Twenty-four horn's after organism identification, an antibioticsensitivity test (Kirby-Bauer disc-diffusion method) confirmed that the organism isolated from our patient was sensitive to all antibiotics used.
Figure 2: Microscopic photograph showing filamentous, branching bacilli (modified Ziehl-Neelsen stain, original magnification X 1000).
Figure 3: Slit-lamp photograph shows a central mild corneal opacity 6 months after treatment.
The patient improved rapidly, with regression of the ocular inflammation and corneal infiltrates, and topical antibiotics were reduced to 2-hour intervals after 1 week. Moreover, topical fluorometholone 0.10% four times a day was added to the antibiotic regimen. One month after surgery, eye examination revealed a moderate leukoma in the central area, but the rest of the cornea was clear. The topical and systemic medications were tapered after 6 weeks.
Six months after surgery, uncorrected visual acuity in the right eye was 20/45, and the spectacle-corrected visual acuity was 20/40. The postoperative spherical equivalent refraction in the right eye was +0.75 -0.75 X 95°. Slit-lamp examination of the right eye showed a clear cornea with a mild rounded scar in the central area (Fig 3), and the postoperative central corneal thickness was 415 µta. The patient's main complaints were night halos and starbursts.
Infectious keratitis is one of the most visionthreatening complications after corneal refractive surgery. Bacterial keratitis has been reported after radial keratotomy10"12, photorefractive keratectomy13,14, and myopic keratomileusis.15 To our knowledge, no previous case of bacterial keratitis related to LASIK has been reported.
Common complications after LASIK are irregular astigmatism, flap displacement, flap wrinkles, dot remnants in the interface, and epithelial implantation in the interface.1517 Noninfectious interface opacities are common within the first postoperative weeks, and are related to epithelial implantation, tear film debris, or foreign particles. These interface opacities after lamellar refractive surgery may sometimes become a diagnostic challenge.
In the presented case, the lesion appearance was suspected of being infectious keratitis, probably related to intraoperative contamination, and a proper microbiologic work-up was undertaken. Lifting the corneal flap and scraping the stromal bed allowed us to obtain abundant material for microbiologic processing and fast microbial identification that guided proper treatment. We believe that the immediate management was the key for the good results in this case.
This case illustrates the risk of microbial keratitis after LASIK retreatment and represents the first infectious keratitis in a series of 745 primary LASIK procedures and 56 LASIK retreatments, with an incidence of 0.12%. This case emphasizes the need for postoperative surveillance, for the use of postoperative topical antibiotics, and for an informed consent about complications for patients who elect corneal refractive surgery.
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