Nocardial Keratitis after Laser in situ Keratomileusis

Post-laser in situ keratomileusis interface fungal keratitis

PURPOSE

To report outcomes of post-laser in situ keratomileusis (LASIK) interface filamentous fungal keratitis.

METHODS

This retrospective interventional case series included 6 eyes of 5 patients with microbiologically proven post-LASIK interface fungal keratitis from August 2008 to August 2013. Patients presenting with concurrent bacterial/viral keratitis, systemic illness, prior ocular pathology, or those without a minimum follow-up of 3 months were excluded. Every case underwent microbiological scrapings from residual bed and undersurface of the flap after flap lift at presentation followed by voriconazole interface wash. Flap amputation was performed when required. The outcome measure was complete resolution of infection.

RESULTS

The mean age was 24 ± 3.1 years. The male:female ratio was 4:1. The mean interval between LASIK and symptom onset was 4.16 ± 2 days; and the mean interval between symptom onset and patient referral was 3.16 ± 1.16 days. Interface scrapings showed filamentous fungal filaments in KOH wet mount. The culture grew Aspergillus in case 1 and case 5. Infiltrated LASIK flap needed to be amputated in 4 eyes of 3 patients. Voriconazole wash (100 μg/mL) of the stromal bed was performed in all cases. A positive response to therapy with resolution of infection was seen in all cases at a mean of 6.5 ± 4.6 days. No intraoperative or postoperative complications after interface scraping or voriconazole wash were observed. The final best-corrected visual acuity ranged from 20/20 to 20/80 at a mean follow-up of 9.1 ± 6.5 months.

CONCLUSIONS

Post-LASIK interface fungal filamentous keratitis can present early and gives good outcomes with early microbiological diagnosis and appropriate management. Voriconazole is an efficient and probably safe adjunct in the armamentarium of corneal surgeons to treat such cases.

Intraoperative and early postoperative flap-related complications of laser in situ keratomileusis using two types of Moria microkeratomes

The purpose of this study is to describe the incidence, management, and visual outcomes of intraoperative and early postoperative flap-related complications of laser in situ keratomileusis (LASIK) surgery using two types of Moria M2 microkeratomes. This retrospective analysis was performed on 806 primary LASIK cases. The intraoperative and early postoperative flap-related complications were identified and categorized according to type of Moria microkeratome. There were 52 intraoperative and early postoperative complications--one case of partial flap (0.124 %), one case of free flap (0.124 %), one case of small flap (0.124 %), 13 cases of epithelial defect (1.61 %), 12 cases of flap striae (1.49 %), 10 cases of diffuse lamellar keratitis (1.24 %), 10 cases of interface debris (1.24 %), three cases of epithelial ingrowth (0.37 %), and one case of microbial infection (0.124 %). The overall incidence of flap complications was 6.45 %. There were 27 right eye (6.73 %) and 25 left eye (6.17 %) complications. The incidence of complications with the Moria automated metallic head 130 microkeratome was 4.22 % and with the Moria single-use head 90 microkeratome was 2.23 %. We observed one culture-negative interface abscess which was cured with surgical cleaning and intensive medical treatment. The most common complication encountered was epithelial defects, followed by flap striae. Our study showed that LASIK with a microkeratome has a relatively low incidence of intraoperative and early postoperative flap complications. The authors have no financial interest in any of the issues contained in this article and have no proprietary interest in the development of marketing of or materials used in this study.

Microbial keratitis after corneal laser refractive surgery

Corneal laser refractive surgery is increasingly being performed on patients with the aim of improving unaided vision. Most candidates for surgery have excellent spectacle- or contact lens-corrected vision. Although microbial keratitis following refractive surgery is a rare complication, and usually has a good visual outcome, it can be sight-threatening. The spectrum of pathogens differs to other causes of microbial keratitis, such as contact lens-associated keratitis, and a different management approach is required. Postoperatively, patients are prescribed topical steroids and broad-spectrum topical antibiotics, typically fluoroquinolones. These do not cover unusual organisms, such as fungi, Nocardia, Acanthamoeba and some atypical mycobacteria. In post-laser-assisted in situ keratomileusis microbial keratitis, the lamellar flap should be lifted to acquire samples for specific microbiological examination, including these atypical organisms. Confocal microscopy is a noninvasive test that provides morphological information, and is operator dependent, but may assist in the rapid diagnosis of fungal, Acanthamoeba or Norcardia keratitis. PCR is not in widespread use, but has high sensitivity and specificity, and may facilitate early diagnosis and specific treatment of the causative organism, which is critical in obtaining the best clinical outcome.

Laser in-situ keratomileusis infection: review and update of current practices

PURPOSE OF REVIEW

To review new clinically relevant data regarding the prevention cause and treatment of laser in-situ keratomileusis (LASIK) infections.

RECENT FINDINGS

Many recent studies of post-LASIK infectious keratitis show the predominance of atypical mycobacteria and Gram-positive cocci and the growing number of other rare pathogens. The American Society of Cataract and Refractive Surgery White Paper treatment paradigm remains the model for initial treatment of LASIK-associated infectious keratitis.

SUMMARY

Improved understanding of the risk factor, different causes, along with a high degree of suspicion on initial presentation is crucial in order to provide the appropriate management in LASIK-associated infectious keratitis.

Brevundimonas vesicularis keratitis after laser in situ keratomileusis

A 45-year-old woman developed a corneal infiltrate 14 months after laser in situ keratomileusis (LASIK) enhancement in the left eye. The LASIK flap was lifted, scraped, and irrigated with fortified vancomycin and ceftazidime. Scraped samples were cultured and grew Brevundimonas vesicularis. The patient remained on topical ceftazidime until improvement was noted and was then switched to topical levofloxacin. The keratitis resolved on antibiotic agents with strong gram-negative coverage and a steroid. To our knowledge, this is the first report of a B vesicularis ocular infection.

Nocardia keratitis

PURPOSE OF REVIEW

Nocardia keratitis is a rarity in most parts of the world. If the diagnosis is timely, and appropriate treatment started, then the visual outcome is good. The purpose of this review is to discuss the recently published literature in relation to the epidemiology, cause, diagnosis, and therapy of Nocardia keratitis.

RECENT FINDINGS

The incidence of Nocardia keratitis, although not well established, appears to be increasing with new species identified with newer molecular methods. The different species causing keratitis are Nocardia. arthritidis, N. neocaledoniensis, N. asiatica, N. asteroids type IV, N. brasiliensis, N. pseudobrasiliensis, N. cyriacigeorgica, N. farcinica, N. otitidiscaviarum, and N. transvalensis. Current therapies with fortified amikacin and newer fluoroquinolones are effective, provided the diagnosis has been made in good time. Ongoing research toward rapid diagnosis using various molecular techniques seems to be promising. Diagnostic microbiology laboratories need to be familiar with these organisms especially in endemic areas, and it is important for the clinician to notify the suspicion of such cases.

SUMMARY

The current recommended treatment is amikacin, and with appropriate therapy, Nocardia keratitis resolves with scarring, with or without vascularization, resulting in good visual outcome.

Outbreak of Nocardia keratitis after photorefractive keratectomy: clinical, microbiological, histopathological, and confocal scan study

Nocardia keratitis occurred in 4 eyes of 3 patients (2 women and 1 man) who had photorefractive keratectomy (PRK) by the same surgeon at the same center. Two eyes of the first 2 patients required lamellar keratectomy to debulk the involved stroma and obtain specimens for microbiological and histopathological evaluation. Light microscopic examination disclosed gram-positive and acid-fast filaments of Nocardia that were confirmed by the microbiological results. Diagnosis of Nocardia keratitis in the third case was not as challenging as in the first 2 cases because of a high index of suspicion. Confocal scans of all cases disclosed hyperreflective and slender, fibril-like structures in the corneal stroma. All eyes responded favorably to topical amikacin and the infection resolved without recurrence. The most probable cause of the outbreak was inadequate attention to sterility during surgery.

Unilateral Candida parapsilosis interface keratitis after laser in situ keratomileusis: case report and review of the literature

PURPOSE

To describe a rare case of early-onset Candida parapsilosis infection after laser in situ keratomileusis (LASIK) and review the published reports of post-LASIK fungal infections.

METHODS

A 32-year-old woman presented with interface infiltration in the central interface in the right eye 2 days after LASIK surgery. The right eye flap was lifted, and the opacities were scraped. Two days later, a 3- x 3-mm-dense oval opacity and diffuse hazes were noted. Surgical intervention was arranged because of suspicion of interface infectious keratitis.

RESULTS

After an apparent post-LASIK keratitis with related interface inflammation failed to respond to medical therapy, corneal culture results were positive for C. parapsilosis 2 weeks 6 days after presentation. The patient was started on topical drops of amphotericin B 0.15% every hour after the smear showed the presence of yeast. The opacities decreased, and the topical antifungal drops were tapered. One month later, her uncorrected visual acuity recovered to 20/20.

CONCLUSIONS

Candida parapsilosis interface keratitis after LASIK may occur in the early phase. Early diagnosis and proper treatment can result in good outcome.

Infectious and noninfectious keratitis after laser in situ keratomileusis

PURPOSE

To retrospectively review the occurrence, treatment, and visual outcomes associated with various etiologies of keratitis as a postoperative complication of laser in situ keratomileusis (LASIK) at an academic surgical center.

SETTING

John A. Moran Eye Center, University of Utah, Salt Lake City, Utah, USA.

METHODS

The charts of 5618 post-LASIK patients (10 477 eyes) were reviewed for the development of keratitis. Occurrence rates, management regimens, and final best spectacle-corrected visual acuity (BSCVA) were reported for infectious and noninfectious keratitis etiologies.

RESULTS

Post-LASIK keratitis was diagnosed in 279 eyes. The keratitis was diagnosed as infectious in 33 eyes (12%) and as noninfectious in 246 eyes (88%). Infectious cases included 5 eyes (15%) with herpes simplex keratitis (HSV), 18 (55%) with adenoviral keratitis, and 10 (30%) with nonviral (including bacterial, fungal, and parasitic) keratitis. Of noninfectious cases, 193 (78%) were classified as diffuse lamellar keratitis (DLK), 36 (15%) as staphylococcal marginal hypersensitivity, and 17 (15%) as localized debris-related keratitis.

CONCLUSIONS

The occurrence of post-LASIK keratitis was 2.66%, with DLK being the most common diagnosis overall. The occurrence of noninfectious keratitis (2.34%) was 7.5 times greater than the occurrence of infectious keratitis (0.31%). Adenoviral keratitis had the best visual outcomes overall, with all 18 patients achieving 20/20 BSCVA. In contrast, all 5 eyes with HSV keratitis lost 1 or 2 lines of BSCVA. Excluding adenoviral keratitis, infectious etiologies had significantly worse visual outcomes than noninfectious etiologies at the 20/40 and 20/20 levels (P = .0013 and P<.001, respectively).

A Cluster of Nocardia Keratitis After LASIK

PURPOSE

To report a cluster of Nocardia asteroides keratitis cases after LASIK.

METHODS

Retrospective review of the history and examination of three patients (four eyes) operated on the same day at a single center who developed postoperative keratitis. All patients underwent lifting of the superficial flap for microbiologic evaluation of the corneal scrapings. The operating surgeon was contacted to identify the possible source of contamination.

RESULTS

Two patients underwent simultaneous bilateral LASIK; however, only one developed postoperative keratitis in both eyes. One patient had unilateral surgery and developed keratitis in the operated eye. Microscopic examination of smears from all eyes revealed thin, branching, acid-fast, filamentous bacteria that were identified as Nocardia asteroides after culture. The infiltrates resolved with topical administration of amikacin sulphate (2.5%) and topical and oral trimethoprim-sulfamethoxazole. Final visual acuity ranged between 20/25 and 20/80. The operating surgeon had used the same blade and microkeratome in all patients.

CONCLUSIONS

Nocardia, a relatively unusual organism, can cause an epidemic of infection after LASIK.

Pseudomonas keratitis after laser in situ keratomileusis

We report a 32-year-old woman who presented with infectious keratitis in the right eye 3 weeks after laser in situ keratomileusis (LASIK). On microbiological investigations, the microorganism isolated was Pseudomonas aeruginosa that was sensitive to ciprofloxacin. To our knowledge, this is the only case report in the literature of post-LASIK infectious keratitis caused by P aeruginosa.

Nocardia keratitis after laser in situ keratomileusis: Clinicopathologic correlation

A case of Nocardia asteroides keratitis occurring 3 weeks after laser in situ keratomileusis (LASIK) in a nontraumatized eye is reported. The patient presented with decreased vision, inflammation, and stromal melting of the LASIK flap, discrete infiltrates, and an anterior chamber cellular reaction. Cultures for acid-fast bacteria grew Nocardia asteroides after 5 days. Infection progressed despite treatment with topical antibiotics and eventually required penetrating keratoplasty (PKP). Postoperatively, the patient was placed on moxifloxacin, a fourth-generation flouroquinolone. The patient experienced a recurrence of Nocardia keratitis at the graft-host interface 2 months after the PKP. This eventually resolved with a combination of topical moxifloxacin and imipenem therapy.

Fluoroquinolone therapy in Mycobacterium chelonae keratitis after lamellar keratectomy

PURPOSE

To characterize a rabbit model of Mycobacterium chelonae keratitis after lamellar keratectomy and assess the effectiveness of fluoroquinolone therapy.

SETTING

University Laboratory, University of California, Irvine, California, USA.

METHODS

Twenty-eight New Zealand white rabbits had unilateral lamellar keratectomy with placement of 2.5 x 10(5) colony-forming units of log-phase M chelonae under each flap. Eyes (7 per group) were randomized and treated with sterile balanced salt solution, gatifloxacin 0.3%, ciprofloxacin 0.3%, or levofloxacin 0.5% 4 times daily. Two masked observers examined all eyes on days 2, 5, and 7 and weekly for 4 weeks. Severity of disease and bacterial culture results were the main outcomes measured. The means and standard deviations were calculated, and differences between the groups were statistically analyzed.

RESULTS

All eyes developed clinical disease. At the time the rabbits were killed, eyes treated with balanced salt solution, ciprofloxacin, levofloxacin, and gatifloxacin were culture positive in 6 (85.7%), 7 (100%), 6 (85.7%), and 3 (42.9%) of 7 eyes per group, respectively. Frequency of positive culture and the severity of clinical disease in gatifloxacin-treated eyes were significantly less (P < .05) than in the other groups combined.

CONCLUSIONS

The rabbit model of M chelonae keratitis was successfully developed in our study. A fourth-generation quinolone (gatifloxacin) showed the best performance among the fluoroquinolones tested in our experimental approach. The fourth-generation fluoroquinolone, gatifloxacin, could be effectively used for the treatment of mycobacterial keratitis.

In Vitro Activity of Fluoroquinolones Against Mycobacterium abscessus and Mycobacterium chelonae Causing Infectious Keratitis After LASIK in Brazil

PURPOSE

To evaluate the in vitro activity of fluoroquinolones against Mycobacterium abscessus and Mycobacterium chelonae isolated from outbreaks of infectious keratitis in Brazil.

MATERIAL AND METHODS

Micobacterial isolates were recovered from infectious keratitis cases related outbreaks that occurred in Brazil after LASIK for myopia. Two outbreaks occurred in Rio de Janeiro in 1998 and 1999, and 3 in São Paulo between 2000 and 2003. All laboratorial analysis, including molecular identification and antibiotic susceptibility testing with determination of the minimum inhibitory concentration (MIC) levels for ciprofloxacin, ofloxacin, gatifloxacin, and moxifloxacin, were performed at Universidade Federal de São Paulo in Brazil.

RESULTS

Fifteen samples were identified as M. chelonae, and 3 were identified as M. abscessus. The outbreaks studied were designated SP-1 in 2000; SP-2 in 2000-2001; and SP-3 in 2003, R1 in 1988 and R2 in 1999. All but 1 of the M. chelonae were resistant to all fluoroquinolones with an MIC90 greater than 32 microg/mL. The only susceptible isolate had MIC levels for ciprofloxacin, ofloxacin, gatifloxacin, and moxifloxacin of 0.38 microg/mL, 0.032 microg/mL, 0.047 microg/mL, and 0.19 microg/mL, respectively. MIC levels for all 3 M. abscessus isolates tested were greater then 32 microg/mL for all fluoroquinolones tested.

CONCLUSIONS

Fluoroquinolone MICs for 17 M. abscessus and M. chelonae isolates recovered from infectious keratitis cases in Brazil indicate that they are not susceptible to these drugs in vitro. Further studies to investigate the in vivo effectiveness of fluoroquinolones against mycobacteria are required because in vitro tests do not support their use in the treatment of micobacterial keratitis in this particular geographic area.

Nontuberculous (atypical) mycobacterial keratitis after LASIK: current status and clinical implications

PURPOSE

Corneal infection with unfamiliar organisms such as nontuberculous (atypical) mycobacteria after laser in situ keratomileusis (LASIK) can be a significant clinical problem, and mismanagement of such corneal infection in an otherwise healthy, young individual can lead to significant medicolegal issues for the refractive surgeon. Because nontuberculous (atypical) mycobacterial keratitis is the most common infection after LASIK, the refractive surgeon should be aware of all aspects of this dreaded infection to be better prepared to manage such cases.

METHODS

Literature search.

RESULTS/CONCLUSIONS

This article provides a comprehensive compilation of all reported cases of nontuberculous (atypical) mycobacterial keratitis in the English literature and provides some useful recommendations for the clinical management of such corneal infection after LASIK.

Unusual anaerobic bacteria in keratitis after laser in situ keratomileusis

Laser in situ keratomileusis (LASIK) was performed in the left eye of a 57-year-old man for residual ametropia after phacoemulsification. The patient was given topical tobramycin and a corticosteroid for 1 week postoperatively. Fifteen days later, he developed 3 corneal infiltrates beneath the flap with a gas bubble, suggesting an anaerobic infection. Tobramycin and ofloxacin were administered every 2 hours, but the condition worsened. Corneal scrapings were taken from beneath the flap for microbiological cultures and a polymerase chain reaction (PCR) test. The PCR amplification was negative for fungi and mycobacteria and positive for bacterial DNA. Sequence analysis showed Propionibacterium granulosum as the causal agent, but cultures were negative. Treatment with vancomycin and cefazolin led to clinical improvement, with resolution of corneal infiltrates. Anaerobic microorganisms can cause keratitis after LASIK. Polymerase chain reaction amplification and DNA typing can help detect microorganisms involved in these ocular infections.

Infections following laser in situ keratomileusis: an integration of the published literature

Infections occurring after laser in situ keratomileusis (LASIK) surgery are uncommon, but the number of reports have steadily increased in recent years. This systematic, comprehensive review and analysis of the published literature has been performed in order to develop an integrative perspective on these infections. We have stratified the data by potential associations, microbiology, treatment, and the degree of visual loss, using Fisher's exact tests and Student's t-tests for analysis. In this review, we found that Gram-positive bacteria and mycobacterium were the most common causative organisms. Type of postoperative antibiotic and steroid use was not associated with particular infecting organisms or severity of visual loss. Gram-positive infections were more likely to present less than 7 days after LASIK, and they were associated with pain, discharge, epithelial defects, and anterior chamber reactions. Fungal infections were associated with redness and tearing on presentation. Mycobacterial infections were more likely to present 10 or more days after LASIK surgery. Moderate or severe visual reductions in visual acuity occurred in 49.4% of eyes. Severe reductions in visual acuity were significantly more associated with fungal infections. Flap lift and repositioning preformed within 3 days of symptom onset may be associated with better visual outcome.

Retinal complications after laser-assisted in situ keratomileusis (LASIK)

PURPOSE OF REVIEW

This paper reviews the retinal complications that may occur after laser-assisted in situ keratomileusis (LASIK).

RECENT FINDINGS

During the review period (1 year), several nonrandomized retrospective studies and case reports/series were published. One study was performed to determine the efficacy and safety of prophylactic laser photocoagulation for retinal breaks in patients with myopia undergoing LASIK. Retinal breaks were identified and treated in 39 eyes (2%). None of the patients developed a rhegmatogenous retinal detachment (RRD) (except one trauma case). Another group studied retinal disease observed in 9239 consecutive eyes after refractive surgery (including LASIK) and found RRD in 11 eyes (0.36%) and choroidal neovascularization (CNV) in 10 eyes (0.33%). Three reports described a total of 16 patients with a previously placed encircling scleral buckle for a RRD who had LASIK to correct myopia. In all patients, the visual acuity (VA) improved. Another study reported the characteristics and surgical outcomes of RRD in myopic eyes after LASIK (33 eyes of 27 patients; frequency 0.08% [33/38, 823]). They found that 45.8% lost two or more lines of VA after vitreoretinal surgery. Two letters described the characteristics and potential mechanisms of a macular lacquer crack (one with subsequent development of subfoveal CNV) in a myopic patients corrected by LASIK.

SUMMARY

Serious complications after LASIK are infrequent. A dilated fundus examination is very important before LASIK and in every patient whose VA after LASIK is not as good as expected to avoid delayed referral to a vitreoretinal specialist if necessary. Only prospective studies can determine whether the procedure exacerbates myopic pathology.

Acremonium fungal infection in 4 patients after laser in situ keratomileusis

We present 4 patients who had laser in situ keratomileusis and were referred to our clinic with a diagnosis of infectious keratitis. Laser in situ keratomileusis was performed in all cases in the same operating room by different surgeons between April and May 2002. A partial penetrating keratoplasty was performed in all patients to control the process. A study of the corneas demonstrated the presence of the fungus Acremonium in all cases. Rigid asepsis during the surgical procedure is important to prevent this serious complication.

Repositioning the Laser in situ Keratomileusis Flap at the Slit Lamp

PURPOSE

To describe the indications and technique for repositioning the laser in situ keratomileusis (LASIK) flap at the slit lamp.

METHODS

We present a description of patients with striae or slippage of the flap who had repositioning of the flap at the slit lamp.

RESULTS

Indications for repositioning at the slit lamp are mostly flap striae. However, it can also be done for a displaced flap and small amounts of debridement. This procedure is not recommended for taking cultures, irrigation of diffuse lamellar keratitis, suturing the flap, or epithelial ingrowth. Repositioning the flap is done by finding the edge of the flap with the cannula, lifting the flap, sweeping the cannula to release the entire wound, and infusing balanced salt solution under the entire flap. We did not encounter infection or recurrent epithelial erosion in these patients.

CONCLUSIONS

Repositioning the LASIK flap at the slit lamp was effective and safe in the treatment of striae or flap slippage. It saved time, money, and, anxiety for the patient.

Ulcerative keratitis caused by Serratia marcescens after laser in situ keratomileusis

We report 2 cases of severe corneal infections caused by Serratia marcescens after laser in situ keratomileusis (LASIK). Twenty-four hours after LASIK, 2 patients developed infectious keratitis, 1 bilaterally. In each eye, the corneal flap was edematous, ulcerated, and detached from the stromal bed. Treatment included removal of the necrotic flap and aggressive antibiotic therapy. Cultures from corneal exudates were positive for S marcescens. After 1 year, both patients had a loss of best corrected visual acuity (BCVA) ranging from 20/40 to 20/22 because of irregular astigmatism. Overrefraction with a hard contact lens resulted in a BCVA of 20/20 in the 3 affected eyes. Slitlamp examination showed trace subepithelial haze without severe corneal scarring. Videokeratography disclosed areas of paracentral inferior steepening resembling keratoconus. Refraction and videokeratography remained stable after 6 months of follow-up. Ulcerative keratitis caused by S marcescens is a potential complication of LASIK. Bilateral involvement may occur if bilateral simultaneous surgery is performed.

Recurrent interface infiltration with hypopyon after astigmatic laser in situ keratomileusis on a penetrating corneal graft

A 56-year-old woman was referred with recurrent interface infiltration and hypopyon after astigmatic laser in situ keratomileusis (LASIK) on a corneal graft. Pseudomonas aeruginosa was isolated as the causative pathogen. Penetrating keratoplasty had been performed 2 years before refractive surgery. After the antibiotic medication was tapered, 3 recurrences of interface infiltration with hypopyon were observed. Penetrating rekeratoplasty was deemed appropriate. Histological examination of the explanted corneal graft revealed anterior stromal neutrophil infiltration. This case illustrates that microbial pathogens brought underneath the flap by LASIK can persist months later despite antimicrobial treatment.

Infectious keratitis after laser in situ keratomileusis: Results of an ASCRS survey

To investigate the incidence, culture results, treatment, and visual outcomes of infectious keratitis after laser in situ keratomileusis (LASIK) worldwide, the Cornea Clinical Committee of the American Society of Cataract and Refractive Surgery (ASCRS) contacted 8600 United States and international ASCRS members by e-mail and asked them to respond to a questionnaire about post-LASIK infectious keratitis. One hundred sixteen infections were reported by 56 LASIK surgeons who had performed an estimated 338 550 procedures. Seventy-six cases presented in the first week after surgery, 7 during the second week, 17 between the second and fourth weeks, and 16 after 1 month. Forty-seven cases were not diagnosed on initial presentation. The most common organisms cultured were atypical mycobacteria and staphylococci. Empiric therapy is not recommended as most of the organisms are opportunistic and not responsive to conventional therapy. Flap elevation and culturing should be performed when post-LASIK infectious keratitis is suspected.

Bilateral Candida parapsilosis interface keratitis after laser in situ keratomileusis

We report a case of Candida infection after laser in situ keratomileusis (LASIK) and review the literature for reports of post-LASIK fungal infections. Risk factors may include postoperative surgical intervention and extended use of topical steroids.

Infectious keratitis after photorefractive keratectomy

PURPOSE

To elucidate risk factors, microbial culture results, and visual outcomes for infectious keratitis after photorefractive keratectomy (PRK).

DESIGN

Multicenter, retrospective chart review, case report, and literature review.

METHODS

The records of 12 patients with infectious keratitis after PRK were reviewed.

MAIN OUTCOME MEASURES

Causative organism, response to medical treatment, and visual outcome.

RESULTS

Infectious keratitis developed in 13 eyes of 12 patients after PRK. Organisms cultured were Staphylococcus aureus (n = 5), including a bilateral case of methicillin-resistant Staphylococcus aureus; Staphylococcus epidermidis (n = 4); Streptococcus pneumoniae (n = 3); and Streptococcus viridans (n = 1). Four patients manipulated their contact lenses, and 2 patients were exposed to nosocomial organisms while working in a hospital environment. Prophylactic antibiotics used were tobramycin (nine cases), polymyxin B-trimethoprim (three cases), and ciprofloxacin (one case). Final best spectacle-corrected visual acuity ranged from 20/20 to 20/100.

CONCLUSIONS

Infectious corneal ulceration is a serious potential complication of PRK. Gram-positive organisms are the most common pathogens. Antibiotic prophylaxis should be broad spectrum and should include gram-positive coverage.

Infectious keratitis after LASIK

PURPOSE

To report the clinical course, management, and outcomes of culture-proven infectious keratitis in 15 eyes of 13 subjects after LASIK.

DESIGN

Retrospective, noncomparative, interventional case series.

PARTICIPANTS

Fifteen eyes of 13 subjects who underwent LASIK and developed culture-positive keratitis.

INTERVENTION

Infectious keratitis was encountered in the operative eyes between 1 day and 450 days. Cultures were obtained, and topical antibiotic therapy was administered in all cases. Some cases required flap lifting, irrigation, and soaking of the bed with antibiotics, flap amputation, or further surgical intervention.

MAIN OUTCOME MEASURES

Time periods from onset to diagnosis, from clinical diagnosis to clinical resolution, final acuities, microbiologic profiles, and medical and surgical interventions were reviewed.

RESULTS

Onset of symptoms of infection varied, depending on the infectious organism. Bacterial organisms tended to present earlier, whereas mycobacterial and fungal organisms had a later mean onset of presentation. Furthermore, the atypical organisms such as mycobacteria, fungus, and acanthamoeba also had a more delayed diagnosis, resulting in a prolonged disease course.

CONCLUSIONS

Infectious keratitis after LASIK is a potentially vision-threatening complication. Onset of symptoms varies depending on causative agents. Furthermore, atypical organisms in the interface or beneath the flap can pose both diagnostic and therapeutic dilemmas. Location in the interface can make it more difficult to culture the organisms and prevent adequate penetration of topical antibiotics.

An outbreak of Mycobacterium chelonae infection after LASIK

OBJECTIVE

To describe an outbreak of mycobacterial keratitis after laser in situ keratomileusis (LASIK), including the microbiologic investigation, clinical findings, treatment response, and outcome.

DESIGN

Retrospective, noncomparative, interventional case series.

PARTICIPANTS

Patients (n = 10) who underwent LASIK surgery between August 22 and September 4, 2000, and developed mycobacterial infection.

METHODS

Patients were prospectively followed in relation to microbiologic investigation, clinical findings, treatment response, and outcome.

MAIN OUTCOME MEASURES

Most patients underwent bilateral simultaneous LASIK. Postoperative infection was signaled by the appearance of corneal infiltrates in the third postoperative week. The microbiologic workup was performed on cultures obtained either by direct scraping of the cornea or by lifting the flap. Medical therapy was instituted based on drug susceptibility testing. Surgical interventions such as corneal debridement and flap removal were performed during recurrences or when there was no satisfactory clinical response.

RESULTS

Cultures revealed Mycobacterium subspecies chelonae. Patients were treated with topical clarithromycin (1%), tobramycin (1.4%), and ofloxacin (0.3%). Oral clarithromycin (500 mg twice a day) was prescribed for those patients who did not respond clinically to topical treatment. Four eyes healed on this regimen. Flap removal was necessary in seven eyes.

CONCLUSIONS

This report highlights mycobacteria as an etiologic infectious agent after LASIK. Diagnosis can be difficult and is often delayed. The treatment mainstay is prolonged antibiotic therapy. Surgical debridement and flap removal may shorten the disease course.

Unilateral fungal and mycobacterial keratitis after simultaneous laser in situ keratomileusis

PURPOSE

To report a case of unilateral fungal and mycobacterial keratitis after simultaneous laser in situ keratomileusis (LASIK).

METHODS

Case report of a 37-year-old woman who developed corneal infiltrates located at the flap-stroma interface in her left eye 3 weeks after LASIK for myopia. The infiltration progressed despite topical antibiotic therapy; therefore, the flap was lifted and irrigated with antibiotic solution. Parallel corneal scrapings were taken. The patient's condition deteriorated, prompting a lamellar keratoplasty.

RESULTS

Corneal scrapings demonstrated no growth. Microbiologic cultures of the corneal specimen were reported as negative, whereas histopathologic examination disclosed fungal filaments. Two months later, the patient presented corneal infiltrates of the left eye again. Because the situation worsened despite therapy, a penetrating keratoplasty was performed. Histopathologic examination of the host cornea revealed no pathogenic species; microbiologic cultures, however, demonstrated Mycobacterium chelonae.

CONCLUSION

Fungi and M. chelonae are rare and insidious causes of infectious keratitis after LASIK. Our case emphasizes the possible difficulties in diagnosing and treating a combined or subsequent infection with both species.

Retinal Detachment in Myopic Eyes After Laser in situ Keratomileusis

PURPOSE

To report the characteristics and surgical outcomes of rhegmatogenous retinal detachments in myopic eyes after laser in situ keratomileusis (LASIK).

METHODS

Clinical charts of patients that developed rhegmatogenous retinal detachment after LASIK were reviewed. Surgery to repair rhegmatogenous retinal detachment was performed in 31 eyes (mean follow-up of 14 months after vitreoretinal surgery).

RESULTS

A total of 38,823 eyes underwent surgical correction of myopia from -0.75 to -29.00 D (mean -6.00 D). Thirty-three eyes (27 patients; frequency .08%) developed rhegmatogenous retinal detachment after LASIK; detachments occurred between 12 days and 60 months (mean 16.3 mo) after LASIK. Eyes that developed a rhegmatogenous retinal detachment had a mean -8.75 D before LASIK. Most rhegmatogenous retinal detachment and retinal breaks occurred in the temporal quadrants (71.1%). Final best spectacle-corrected visual acuity (BSCVA) of 20/40 or better was obtained in 38.7% of the 31 eyes (two patients refused surgery). Poor final visual acuity (20/200 or worse) occurred in 22.6% of eyes. Information regarding visual acuity after LASIK and before the development of rhegmatogenous retinal detachment was available in 24 eyes; 45.8% (11/24 eyes) lost two or more lines of visual acuity after vitreo-retinal surgery. Reasons for poor visual acuity included the development of proliferative vitreo-retinopathy (n=5), epiretinal membrane (n=1), chronicity of rhegmatogenous retinal detachment (n=1), new breaks (n=1), displaced corneal flap (n=1), and cataract.

CONCLUSIONS

Rhegmatogenous retinal detachment after LASIK for myopia is a serious complication. Final visual acuity may be limited by myopic degeneration, amblyopia, or delayed surgical repair.

Anterior uveitis after laser in situ keratomileusis

PURPOSE

To report a case series of anterior uveitis after laser in situ keratomileusis (LASIK) and the incidence of anterior uveitis at a mean of 3 years.

SETTING

Centro Medico Docente La Trinidad and Clinica Oftalmologica Centro Caracas, Caracas, Venezuela.

METHODS

Five refractive surgeons and 18488 eyes that had surgical correction of a mean ametropia of -2.23 diopters (D) (range -10.25 to +4.25 D) participated in the study; 74.3% of the eyes were myopic. Laser in situ keratomileusis was performed in all eyes. Patients were followed for a mean of 36 months (range 6 to 48 months) after LASIK. The clinical charts of patients who developed uveitis after LASIK were reviewed. The mean preoperative intraocular pressure (IOP) was 15.2 mm Hg (range 12 to 19 mm Hg). The mean corneal ablation depth was 37.47 micro m (range 12 to 98 micro m). In the immediate postoperative period, all patients received a combination of topical dexamethasone and tobramycin.

RESULTS

Thirty-five eyes (18 patients) developed anterior uveitis after LASIK. Signs and symptoms appeared a mean of 20.7 days (range 17 to 28 days) postoperatively and 5.08 days (range 2 to 8 days) after withdrawal of topical steroid and antibiotic agents. Eyes that developed LASIK-related uveitis had a mean preoperative spherical equivalent of -2.32 D (range -7.00 to +4.25 D). Intraocular pressure dropped to a mean of 8.0 mm Hg (range 4 to 12 mm Hg) at the onset of uveitis (P <.0001). The LASIK-related anterior uveitis resolved and IOP returned to baseline after a mean of 3 days on topical steroid and cycloplegic agents. Laboratory and immunology (including human leukocyte antigen-B27) tests were negative in 15 of 18 patients (83.33%). The incidence of uveitis after LASIK was 0.18%.

CONCLUSIONS

Anterior uveitis after LASIK is infrequent. It may be due to uveal trauma during surgery with disruption of normal anterior-chamber-associated immune deviation, decreased antiinflammatory cytokines, and increased proinflammatory cytokines. Further studies are needed to investigate the mechanisms of this association.

Delayed-onset mycobacterial keratitis after LASIK

PURPOSE

To describe the time course, diagnosis, clinical features, and treatment of seven patients with Mycobacterium szulgai keratitis that developed from 7 to 24 weeks after laser in situ keratomileusis (LASIK).

METHODS

Seven of 30 eyes of 18 patients were identified with keratitis after LASIK. The first two patients presented 12 to 14 weeks after LASIK; nontuberculous mycobacteria were identified 1 month after the flaps were cultured. Patient recall identified three additional cases by culture and two cases by clinical features alone. Pulsed-field gel electrophoresis (PFGE) was used to type the isolates, and treatment was modified based on susceptibilities.

RESULTS

M. szulgai was identified in five patients for whom cultures were performed, but response to empiric therapy based on cultures proved unsatisfactory. The keratitis resolved in all patients with treatment including clarithromycin based on susceptibilities. Medical therapy was sufficient, although one patient required flap amputation. Six of seven patients recovered best-corrected visual acuity (BCVA), while one patient lost one line of BCVA. Two patients lost one line of postoperative uncorrected visual acuity (UCVA), two patients gained one line of UCVA, and three patients recovered postoperative UCVA. PFGE analysis revealed that the M. szulgai strains were identical, and the infection source was contaminated ice used to chill syringes for saline lavage.

CONCLUSIONS

Nontuberculous mycobacterial keratitis after LASIK is a diagnostic and management challenge, but outcomes can be preserved with treatment based on susceptibilities. This cluster underscores the importance of adherence to sterile protocol during LASIK.

Interface fungal infection after laser in situ keratomileusis presenting as diffuse lamellar keratitis. A clinicopathological report

PURPOSE

To report clinicopathological analyses of 3 cases of interface fungal infection following laser in situ keratomileusis (LASIK) and diffuse lamellar keratitis (DLK).

SETTING

Center for Research on Ocular Therapeutics and Biodevices and Arthur and Holly Magill Research Center for Vision Correction, Storm Eye Institute, Medical University of South Carolina, Charleston, South Carolina, USA.

METHODS

Clinicopathological analysis of 5 eyes of 3 patients who developed culture-proven interface fungal infection after LASIK was performed. Detailed pathological analysis of the amputated flap from 1 case included light, scanning, and transmission electron microscopy.

RESULTS

Culture and pathological analysis revealed Candida albicans in all 3 cases. Common links among the cases were early onset of DLK following intensive corticosteroid and antibiotic treatment and later onset of interface fungal infection. All cases resolved, and good visual acuity was restored after medical treatment with antifungal agents.

CONCLUSIONS

Interface fungal infection after LASIK can be sight-threatening. Early lifting of the flap, fungal culture, and aggressive antifungal treatment are required to treat this complication and avoid deleterious sequelae.

Microbial Keratitis After Laser in situ Keratomileusis

PURPOSE AND METHOD

To review the literature on microbial keratitis reported after laser in situ keratomileusis (LASIK).

RESULTS

Forty-one eyes have been reported to have microbial keratitis after LASIK. The causative organisms vary from gram positive bacteria to atypical mycobacteria, fungal, and viral pathogens. The infection is usually acquired intraoperatively, but may also be caused by postoperative contamination. A majority of the patients present within 72 hours of the surgery with an acute onset of symptoms. Management of microbial keratitis after LASIK includes aggressive topical fortified antibiotic therapy, irrigation of stromal bed with antibiotic solution after lifting the flap, and sending the scraping of the infiltrate for microbiological evaluation. The keratitis heals with scarring and a best spectacle-corrected visual acuity of 20/40 or better can be obtained in the majority of the patients.

CONCLUSION

Microbial keratitis is a sight-threatening complication of LASIK.

Delayed-onset multifocal polymicrobial keratitis after laser in situ keratomileusis

We report a case of mixed Aspergillus fumigatus and coagulase-negative Staphylococcus stromal keratitis in a 43-year-old man who developed discomfort and swelling in his right eye 20 days after uneventful bilateral laser in situ keratomileusis (LASIK). Clinical examination revealed 2 distinct corneal infiltrates beneath the LASIK flap. Corneal scrapings were taken for microscopic examination and culture. Both infiltrates initially improved on topical antibiotic therapy, but over the next 18 days, 1 infiltrate worsened and repeat cultures were performed, which demonstrated A fumigatus. Natamycin 5% and amphotericin 0.1% were started and continued for 8 weeks with resolution of the infiltrate and return of the best corrected visual acuity. Delayed-onset multifocal keratitis is a rare complication of LASIK. Fungal entities should be considered in the differential diagnosis.

Infectious post-LASIK crystalline keratopathy caused by nontuberculous mycobacteria

PURPOSE

To report three cases of infectious crystalline keratopathy caused by non-tuberculous mycobacteria after LASIK surgery.

METHODS

Interventional case reports and literature review.

RESULTS

Infectious keratitis with clinical features of crystalline keratopathy after LASIK is described. Culture revealed Mycobacterium chelonae from the corneal scrapings of the three patients, all of whom underwent medical and surgical (debridement) treatment.

CONCLUSIONS

Mycobacteria may cause infectious crystalline keratopathy after LASIK. The presence of crystalline keratopathy in patients that underwent LASIK must be considered an indicator of nontuberculous mycobacteria infection. Microbiologic work-up of a corneal specimen is required for the institution of appropriate therapy.

A Cluster of cases of Mycobacterium szulgai keratitis that occurred after laser-assisted in situ keratomileusis

Laser-assisted in situ keratomileusis (LASIK) is a recently developed ophthalmic procedure. When 2 patients developed keratitis caused by Mycobacterium szulgai after they underwent LASIK surgery, we conducted a retrospective cohort study of all LASIK procedures performed at Scott & White Clinic (Temple, Texas) during a 4.5-month period. Seven patients had compatible symptoms and signs, 5 of whom had confirmed M. szulgai keratitis. Five cases occurred among 30 procedures performed by doctor A, and there were no cases among 62 procedures performed by doctor B (approximate relative risk, 12.0; 95% confidence interval, 1.6-679.0; P=.0029). Doctor A had chilled syringes of saline solution in ice for intraoperative lavage-the only factor that differentiated the procedures of the 2 surgeons. Cultures of samples from the source ice machine's drain identified M. szulgai; the strain was identical to isolates recovered from all confirmed cases and differed from 4 standard M. szulgai strains, as determined by pulsed-field gel electrophoresis. Intraoperative contamination from ice water apparently led to M. szulgai keratitis in these patients.

Pneumococcal keratitis at the flap interface after laser in situ keratomileusis

A 28-year-old woman had uneventful laser in situ keratomileusis in the right eye. Six days postoperatively, she reported ocular pain and a large corneal stromal infiltrate was observed at the flap interface. A second surgery including lifting and excising the flap and scraping the stromal bed was performed. Topical antibiotics were prescribed. A bacterial culture revealed Streptococcus pneumoniae. The keratitis responded well to topical vancomycin. Twelve days after the second surgery, the stromal infiltrate had regressed, the hypopyon had resolved, and visual acuity was hand movements at 0.5 m.

Cluster of Mycobacterium chelonae keratitis cases following laser in-situ keratomileusis

PURPOSE

To describe a cluster of Mycobacterium chelonae keratitis cases involving patients who underwent laser in-situ keratomileusis (LASIK) at a single refractive surgery center.

DESIGN

Descriptive case series of four patients and cohort study to identify disease associations.

METHODS

Examination schedules, diagnostic tests, and therapy were based on best medical judgment. Isolates from three patients were compared by pulsed-field gel electrophoresis. Epidemiologic studies were performed to identify the source of infection.

RESULTS

Seven of eight eyes developed M. chelonae keratitis following bilateral simultaneous LASIK. Each patient was thought to have diffuse lamellar keratitis initially, but all seven eyes were noted to have opacities suggestive of infectious keratitis by 13 to 21 days after surgery. All eyes had undergone hyperopic LASIK over four days in April 2001 by one surgeon in a community-based refractive surgery center. A cohort study of all patients undergoing LASIK at the same center in April 2001 revealed that M. chelonae keratitis occurred only in persons undergoing correction of hyperopia (seven of 14 eyes vs. none of 217 eyes undergoing myopic LASIK, P <.001). The only difference identified between procedures was use of masks created from a soft contact lens in hyperopic LASIK. Three isolates (three patients) were indistinguishable by pulsed-field gel electrophoresis. Eyes were treated with a combination of antimicrobial agents, including topical azithromycin in three patients, with resolution of infection in all eyes over 6 to 14 weeks. The source of infection was not identified on environmental cultures.

CONCLUSION

Postoperative nontuberculous mycobacterial keratitis can occur in an epidemic fashion following LASIK. Topical amikacin, azithromycin, clarithromycin, ciprofloxacin, or a combination of these agents, appears to be effective treatment for these infections.

LASIK complications: etiology, management, and prevention

Laser in situ keratomileusis (LASIK) is a rapidly evolving ophthalmic surgical procedure. Several anatomic and refractive complications have been identified. Anatomic complications include corneal flap abnormalities, epithelial ingrowth, and corneal ectasia. Refractive complications include unexpected refractive outcomes, irregular astigmatism, decentration, visual aberrations, and loss of vision. Infectious keratitis, dry eyes, and diffuse lamellar keratitis may also occur following LASIK. By examining the etiology, management, and prevention of these complications, the refractive surgeon may be able to improve visual outcomes and prevent vision-threatening problems. Reporting outcomes and mishaps of LASIK surgery will help refine our approach to the management of emerging complications.

Infectious keratitis after laser refractive surgery

PURPOSE

To report two cases of infectious keratitis, one fungal after photorefractive keratectomy (PRK) and the other bacterial after laser in situ keratomileusis (LASIK).

DESIGN

Two interventional case reports.

PARTICIPANTS

Case 1 is a male who was seen 3 weeks after PRK with a corneal ulceration. Case 2 involves a female who was seen 7 weeks after LASIK with interface granularity.

RESULTS

Cultures in case 1 were identified as Scopulariopsis species, and despite intensive treatment, a therapeutic penetrating keratoplasty (PK) was eventually performed. Case 2 had cultures identified as Mycobacterium chelonae and also ultimately required a therapeutic PK.

CONCLUSIONS

Two unusual infectious keratitides are reported after different laser refractive surgery techniques.

A prospective, randomized comparison of the use versus non-use of topical corticosteroids after laser in situ keratomileusis

OBJECTIVE

To evaluate the benefit and safety of topical corticosteroids after laser in situ keratomileusis (LASIK).

DESIGN

Prospective, randomized, double-masked clinical trial.

PARTICIPANTS

A consecutive series of 1747 eyes in 897 patients desiring surgical correction of myopia from plano to -16 diopters (D) with up to 6 D of astigmatism.

INTERVENTION

Patients were randomly assigned to topical corticosteroids or artificial tears.

MAIN OUTCOME MEASURES

The primary outcome measure was stability of refraction. Secondary outcome measures were differences in best-corrected visual acuity, decrease in spherical refractive myopia, improvement in uncorrected visual acuity, predictability of achieved corrections versus planned corrections, evaluation of postoperative haze, preservation of best-corrected visual acuity, intraocular pressure, and incidence of complications and adverse events.

RESULTS

No difference was found between the groups for refractive accuracy, best-corrected or uncorrected visual acuity, or safety. Topical corticosteroids were associated with a prolonged period of refractive regression in moderate to high myopes (-7.25 to -16.00 D) (P = 0.01). Increased haze was noted at the 1 week examination for eyes not receiving topical steroids (P = 0.008); however, in most cases this was clinically insignificant. Thirty-six eyes (2.1%) required supplemental topical corticosteroids unrelated to reoperation. Two eyes received these on the first postoperative day and 15 at the 1-week examination.

CONCLUSIONS

Topical corticosteroids did not seem to play any beneficial role in routine postoperative treatment after LASIK, and they were associated with decreased stability of refraction in more highly myopic eyes. Eyes that require additional topical corticosteroids are easily identified at either the initial postoperative examinations or during the course of routine postoperative care.

Complications of Laser in situ Keratomileusis: Etiology, Prevention, and Treatment

PURPOSE

To review the etiology, prevention, and management of laser in situ keratomileusis (LASIK) complications.

METHODS

Review of literature and the experience of the authors.

RESULTS

Careful preoperative screening is critical to prevention of many potential complications of LASIK. Flap complications that occur during surgery are typically managed by replacement of the flap and repeating the surgery or applying special methods such as transepithelial photorefractive keratectomy weeks to months following the initial procedure. A common source of serious complications is the use of a microkeratome that functions after improper assembly. Timely treatment of postoperative complications such as diffuse lamellar keratitis, flap striae, and infection is critical to an optimal outcome.

CONCLUSION

Most complications of LASIK can be treated effectively and have minimal effect on the final outcome after surgery, if appropriate methods are used for management.

Aspergillus fumigatus keratitis after laser in situ keratomileusis

PURPOSE

To report a case of Aspergillus fumigatus keratitis after a laser in situ keratomileusis (LASIK) enhancement procedure.

METHOD

Case report.

RESULTS

A 56-year-old woman developed an ulcer in the flap 13 days after LASIK enhancement. A 4-week course of fortified antibiotics for a presumed bacterial infection followed. The ulcer progressed, causing 60% thinning of the corneal stroma. A biopsy was performed 5 weeks after onset of symptoms, and antifungal agents were initiated. Cultures showed A. fumigatus. Her cornea perforated after the biopsy, requiring cyanoacrylate and lamellar overlay sutures, but the infiltrate resolved on antifungal agents.

CONCLUSION

This report is the first description of Aspergillus keratitis after LASIK. We hypothesize that the infection became established on the stromal bed during surgery and led to melting, anteriorly through the flap and posteriorly through the stroma. Diagnosis was made by a corneal biopsy and inoculation of a wide array of media. This case demonstrates the need to consider atypical organisms, including fungi, in the differential diagnosis of post-LASIK infections when there is no response to therapy and highlights the role of corneal biopsy and flap lifting in the diagnosis of this condition.

Ocular nocardia infections with special emphasis on the cornea

Nocardia are aerobic, gram-positive, nonmotile and branching filamentous bacteria. Corneal infection by Nocardia is rare. Trauma is the most common predisposing factor. Isolated case reports of nocardial infection associated with contact lens wear and laser in situ keratomileusis (LASIK) have been reported. The clinical picture usually consists of superficial patchy infiltrates, which may be arranged in a wreath pattern. Presence of gram-positive, branching, beaded filaments that stain with 1% acid-fast stain (using 1% sulfuric acid, modified Kinyoun's method) in smears of corneal scrapings is suggestive of nocardial infection. Nocardia grow on commonly used media as tiny, white, dry colonies. Available knowledge and clinical experience suggest that although sulfacetamide eyedrops can be tried as the initial drug, trimethoprim-sulfamethoxazole and amikacin are effective drugs. Once therapy is initiated, the infiltrate responds promptly and resolves, forming a corneal scar with or without vascularization, and good visual recovery can be expected.