Microbial Colonization and Antibacterial Resistance Patterns after Boston Type 1 Keratoprosthesis

Antibacterial and cytocompatible silver coating for titanium Boston Keratoprosthesis

The Boston Keratoprosthesis (BKPro) serves as a medical solution for restoring vision in complex cases of corneal blindness. Comprising a front plate made of polymethylmethacrylate (PMMA) and a back plate of titanium (Ti), this device utilizes the beneficial biomaterial properties of Ti. While BKPro demonstrates promising retention rates, infection emerges as a significant concern that impacts its long-term efficacy. However, limited research exists on enhancement of BKPros through intrinsic infection-preventing mechanisms. In this regard, metal ions, especially the well-known Ag+ ions, are a promising alternative to obtain implants with innate antibacterial properties. However, little information is available about the effects of Ag in corneal tissue, especially within human corneal keratocytes (HCKs). In this work, an electrodeposition treatment using a constant pulse is proposed to attach Ag complexes onto rough Ti surfaces, thus providing antibacterial properties without inducing cytotoxicity. Complete physicochemical characterization and ion release studies were carried out with both control and Ag-treated samples. The possible cytotoxic effects in the short and long term were evaluated in vitro with HCKs. Moreover, the antibacterial properties of the silver-treated surfaces were tested against the gram-negative bacterial strain Pseudomonas aeruginosa and the gram-positive strain Staphylococcus epidermidis, that are common contributors to infections in BKPros. Physicochemical characterization confirmed the presence of silver, predominantly in oxide form, with low release of Ag+ ions. Ag-treated surfaces demonstrated no cytotoxicity and promoted long-term proliferation of HCKs. Furthermore, the silver-treated surfaces exhibited a potent antibacterial effect, causing a reduction in bacterial adhesion and evident damage to the bacterial cell walls of P. aeruginosa and S. epidermidis. The low release of Ag+ ions suggested reactive oxygen species (ROS)-mediated oxidative stress imbalance as the bactericidal mechanism of the silver deposits. In conclusion, the proposed electrodeposition technique confers antibacterial protection to the Ti backplate of BKPro, mitigating implant-threatening infections while ensuring non-cytotoxicity within the corneal tissue.

Endophthalmitis in Eyes With the Boston Type I Keratoprosthesis: Incidence, Recurrence, Risk Factors, and Outcomes

PURPOSE

To determine the incidence and recurrence of Boston type I keratoprosthesis (KPro)-associated endophthalmitis, and its microbiological profile, risk factors, and outcomes.

METHODS

This is a retrospective study of 158 consecutive KPro procedures with a median follow-up of 78.4 months. Medical charts were reviewed for ocular history, contact lens and topical antibiotic use, visual acuity, and complications. For eyes with endophthalmitis, time to infection, culture results, and recurrences were collected. Cox regression analyses identified risk factors for endophthalmitis and compared the risk for visual failure, KPro retention, and globe loss between eyes with and without endophthalmitis.

RESULTS

The incidence and recurrence rates of endophthalmitis were of 1.7% and 6.0% per procedure-year, respectively. First episodes occurred at a median of 18.6 months. Eight of 18 episodes (44%) were culture positive, isolating mainly Gram-positive bacteria (7 [88%]). Previous ocular burn (hazard ratio: 7.34, 95% confidence interval: 1.91-28.15), infectious keratitis (5.09, 1.70-15.22), corneal melt (4.55, 1.50-13.83), and postoperative contact lens wear (4.19, 1.17-15.04) were risk factors. Eyes with endophthalmitis did not have a higher risk for visual failure (1.74, 0.78-3.91) but were more likely to not retain the KPro (2.81, 1.15-6.88) and undergo evisceration (2.81, 1.15-6.88). All eyes lost ≥ 2 lines of vision during the endophthalmitis episode.

CONCLUSIONS

Endophthalmitis is rare but vision and globe threatening in eyes with KPro. Given the increased associated risk, corneal melts and infectious keratitis must be promptly treated, postoperative contact lenses should be considered on a case-by-case basis, and patients with ocular burns might require more aggressive antimicrobial prophylaxis.

Infectious Keratitis After Boston Type 1 Keratoprosthesis Implantation

PURPOSE

To identify the incidence, risk factors, and outcomes of infectious keratitis after Boston type 1 keratoprosthesis (kpro) implantation.

METHODS

Retrospective case series of kpro procedures at the Stein Eye Institute and the Centre Hospitalier de l'Université de Montréal between May 1, 2004, and December 31, 2018. Data were collected regarding ocular history, operative details, postoperative management, microbiologic profile, treatment, and outcomes. Log-rank test and Cox proportional hazard ratio (HR) were used to evaluate for an association between risk factors and outcomes.

RESULTS

A total of 349 kpro procedures were performed in 295 eyes of 268 patients. Fifty-seven cases of presumed infectious keratitis were identified after 53 procedures (15.2%) in 50 eyes (16.9%) of 49 patients (18.3%). The incidences of culture-positive bacterial and fungal keratitis were 0.014 and 0.004 per eye-year, respectively. Persistent corneal epithelial defect formation (P < 0.001) and cicatricial disease (HR: 1.98, 95% confidence interval, 1.02-3.83) were associated with a significantly higher incidence of infectious keratitis. For the 53 cases with a known outcome, medical therapy achieved resolution of infection in 34 cases (64.2%), whereas kpro explantation was required in 19 cases (35.8%). Infectious keratitis was associated with an increased risk for kpro explantation (HR: 3.09, 95% confidence interval, 1.92-4.79).

CONCLUSIONS

Infectious keratitis develops in approximately 17% of eyes after kpro implantation, with a higher rate of culture-positive bacterial than fungal keratitis. The observed rate of microbial keratitis suggests the need for additional topical antimicrobial prophylaxis in eyes at higher risk, such as those with preexisting cicatricial disease or postoperative persistent corneal epithelial defect formation.

Diphtheroids as Corneal Pathogens in Chronic Ocular Surface Disease in Stevens-Johnson Syndrome/Toxic Epidermal Necrolysis

PURPOSE

To characterize diphtheroid corneal infections in eyes in the chronic phase of Stevens-Johnson syndrome/toxic epidermal necrolysis (SJS/TEN).

METHODS

Observational case series.

RESULTS

Four eyes of 3 patients were included in this review. Each eye presented with persistent corneal epithelial defect with corneal thinning in the chronic phase of SJS/TEN. None of the epithelial defects were associated with stromal infiltration. The corneas were cultured at the time of workup of persistent epithelial defect (3 eyes) or at time of tectonic penetrating keratoplasty after perforation (1 eye). Cultures yielded abundant growth of Corynebacterium spp., including Corynebacterium jeikeium (n = 2), Corynebacterium glucuronolyticum (n = 1), and a multidrug-resistant Corynebacterium striatum isolate (n = 1). The ocular surface was stabilized with surgical intervention (1 eye) or with introduction of fortified topical antibiotic based on laboratory identification and susceptibility testing of the isolated organisms (3 eyes). Numerous risk factors for microbial keratitis were present in all 4 eyes.

CONCLUSIONS

In eyes with a persistent corneal epithelial defect in the chronic phase of SJS/TEN, even in the absence of an infiltrate, corneal culture should be undertaken. Recognition and treatment of Corynebacterium spp. as opportunistic pathogens may lead to favorable outcomes in cases of clinically sterile ulceration during the chronic phase of SJS/TEN.

Ocular Surface Microbial Flora in Patients with Chronic Limbal Stem Cell Deficiency Undergoing Cultivated Oral Mucosal Epithelial Transplantation

PURPOSE:

The purpose of this study is to analyze the ocular surface microbial flora in patients with chronic limbal stem cell deficiency (LSCD) due to Stevens–Johnson Syndrome (SJS) and ocular chemical injury undergoing cultivated oral mucosal epithelial transplantation (COMET).

METHODS:

Patients of SJS and chemical injury who had bilateral total LSCD planned for COMET were studied. Conjunctival swab was taken before surgery. Parameters evaluated were organism cultured, sensitivity pattern, frequency of positive culture, and clinical impact on management strategy.

RESULTS:

Thirteen patients were included in which nine were males and four females. All patients had positive conjunctival swab culture. Most common organism isolated was Staphylococcus epidermidis, followed by Staphylococcus aureus and Pseudomonas aeruginosa. The staphylococcal species isolated were sensitive to all the conventional antibiotics while Pseudomonas cultured showed resistance to cefuroxime, ceftriaxone, and ceftazidime. Repeat conjunctival swab sent after a week of topical antibiotic therapy yielded positive culture of the same organism twice in 25% (3/12), thrice in 58.3% (7/12), and four times in 16.6% (2/12) of the patients. One patient had a polymicrobial flora with positive yield of S. aureus (thrice), S. epidermidis (twice), and P. aeruginosa (twice) in consecutive conjunctival swab culture in the absence of clinical infection. Two patients with persistent positive cultures had to undergo repeat oral mucosal harvesting as the transplantation of the cultivated explants had to be deferred.

CONCLUSION:

Ocular surface in LSCD patients yielded pathogenic organisms on culture. Poor ocular surface with absent tear film could be the contributing factors. It is important to perform the conjunctival swab culture before COMET surgery.

[Boston keratoprosthesis type 1]

Penetrating keratoplasty is the most commonly performed tissue transplant in the world. However, its success depends on the health of the ocular surface and the intact immune privilege of the eye. In the absence of these two conditions, corneal transplants have an increased failure rate and result in corneal blindness. For more than two hundred years, researchers have been trying to find the best design of the artificial cornea in order to address these cases of severe corneal blindness. Despite previous difficulties, interest in the field has recently been revived, and considerable progress has been made over the last 20 years, to the point where the keratoprosthesis is now considered a primary procedure for some indications and is no longer always a surgery of last resort. In this review, we describe the global and personal experience with Boston keratoprosthesis type 1. It is a relatively new treatment for severe corneal blindness in the context of multiple failed corneal transplants and high-risk conditions. In the last decade, changes in the design, surgical technique, and postoperative management have increased the success rate and popularity of the Boston keratoprosthesis and decreased its complications substantially, making it a safe and effective alternative for certain corneal pathologies. However, some complications persist and require management to improve the visual prognosis of patients with corneal blindness.

Keratoprosthesis prophylaxis: is it time for a paradigm shift?

The Boston Type I Keratoprosthesis has been improving in both design and safety since its inception. Due to particular features inherent in the Boston Type I Keratoprosthesis eye and certain aspects of the ocular surface, special attention is required to maintain these implanted devices. There is currently a prominent role for keratoprosthesis prophylaxis; it is designed to prevent infectious complications like keratitis and endophthalmitis. This standard-of-care therapy has anecdotally been shown to improve outcomes; however, it has not been examined in the setting of controlled clinical trials. Moreover, concerns remain with the chronic utilization of topical antibiotics in that they may engender antibiotic resistance and select for opportunistic populations to establish a foothold on the ocular surface. We believe and introduce the idea that there is merit in exploring other compounds besides antibiotics for prophylaxis such as antiseptics like povidone-iodine. Specifically developed formulations of povidone-iodine may prove useful in both improving keratoprosthesis safety and simultaneously mitigating concerns regarding antibiotic resistance.

Boston Type I Keratoprosthesis: Antibacterial Resistance and Microbiota Evaluation of Soft Contact Lenses

PURPOSE

To evaluate microbiota colonizing soft contact lenses (CL) in eyes with Boston type I keratoprosthesis (BKPro), and determine the prevalence of resistance to fourth-generation fluoroquinolone (FQ).

DESIGN

Prospective, observational study.

SUBJECTS

Patients with BKPro using CL as routine who were in postoperative follow-up in the Department of Ophthalmology of the Federal University of Sao Paulo, and volunteered to participate in the study. All patients were under a prophylactic scheme of topical 0.5% moxifloxacin 3 times a day and topical 5% povidone-iodine (PI) at the time of CL exchange.

METHODS

Patients on scheduled replacement scheme of CL had their lenses removed and sent for microbiological analysis. Standard culture methods were used for microorganism identification and susceptibility to different antibiotics was tested. Main outcome measure was prevalence of resistance to fourth-generation FQ.

RESULTS

Among the 19 eyes, 12 eyes (63%) had at least 1 positive bacterial culture. The most prevalent isolates were Staphylococcus epidermidis and other coagulase-negative staphylococci. Actinomyces viscosus was isolated in 1 CL. Fungal cultures were all negative. Of the 12 eyes with culture bacterial growth, resistance to fourth-generation FQ (0.5% moxifloxacin) was identified in 6 different eyes (50%). None presented infectious complications.

CONCLUSIONS

FQ-resistant bacteria were isolated in some patients. Although our prophylactic antibiotic regimen has been efficient in preventing bacterial infection, this analysis demonstrated that prophylaxis with PI and low FQ dose might increase resistance to antibiotics. Investigations in this field may help to outline future changes of prophylactic guidelines and therapeutic strategies.

Outcomes of bilateral sequential implantation of the Boston keratoprosthesis type 1

OBJECTIVE

To evaluate the risks and benefits of sequential bilateral Boston type 1 keratoprosthesis (KPro) implantation for bilateral corneal blindness.

DESIGN

Comparative retrospective study.

PARTICIPANTS

Patients who underwent a sequential bilateral KPro surgery.

METHODS

All 11 patients who underwent sequential bilateral KPro surgery at the Centre Hospitalier de l'Université de Montréal between October 2008 and October 2011 were recruited. Data from the 22 patient eyes in our study were separated in 2 groups based on the first (group 1) or second eye (group 2) implanted with the Kpro. Both groups were then compared for the best corrected visual acuity (BCVA) and complications. Bilateral BCVA following both surgeries and the overall number of complications that affected each patient after both interventions were also analyzed.

RESULTS

At 24 months, BCVA was 20/150 in group 1 and 20/200 in group 2 (p = 0.67). Throughout the study, there was no significant difference in BCVA between the 2 groups (p > 0.05), and bilateral BCVA was similar. The complication rate was comparable in the 2 groups. Patients had a mean of 2.45 complications following the first surgery and a mean of 5.27 in both eyes combined after the second intervention (p = 0.03).

CONCLUSIONS

Because visual gain observed following the second surgery was the same as that with the first and multiple surgeries increased the number of complications for each patient, we recommend saving bilateral KPro implantation for cases in which the first eye with KPro develops a disease limiting its visual potential.

Microbial Keratitis and Endophthalmitis After the Boston Type 1 Keratoprosthesis

PURPOSE

To determine the incidence, ocular surface disease associations, microbiological profile, and clinical course of postoperative infections after implantation of the Boston type 1 keratoprosthesis (KPro-1).

METHODS

A retrospective chart review was conducted of all cases of the KPro-1 performed at a tertiary eye care center between January 1, 2008, and December 31, 2014.

RESULTS

Seventy-five KPro-1 procedures were included in the analysis. Postoperative infections occurred in 13 eyes (17.3%) with an incidence of 0.064 cases per eye-year. The Kaplan-Meier probability of an infection-free graft was 0.96, 0.90, 0.88, 0.87, and 0.86 at years 1 through 5, respectively. The rate of infections was greater in eyes with ocular surface disease (26.3% vs. 8.1%, P = 0.06), especially in those with a history of chemical or thermal injury or herpes zoster keratopathy (P = 0.001). There were 8 cases (10.7%) of microbial keratitis due to either fungi (5 cases) or bacteria (3 cases). There were 7 cases (9.3%) of endophthalmitis due to bacteria (5 cases) or intraocular extension of fungal keratitis (2 cases). The incidence of microbial keratitis and endophthalmitis was 0.034 and 0.03 cases per eye-year, respectively. Therapeutic management of the infected eyes required graft and device removal in 7 eyes (53.8%). After completion of microbiologic treatment, 7 eyes (53.8%) had lost more than 2 lines of the best-corrected preinfection visual acuity, including 5 eyes with endophthalmitis that had hand motion vision or worse.

CONCLUSIONS

Postoperative infections are a serious issue that compromises device retention and visual outcomes after keratoprosthesis implantation.

Current Concepts in the Management of Unique Post-keratoplasty Infections

As corneal transplantation has evolved, the spectrum of post-surgical infection has changed and often presents a diagnostic and therapeutic challenge. Lamellar techniques hold the potential of improved outcomes and decreased post-operative complications, however, they create a lamellar interface, which is a potential space for sequestration of infectious organisms. In addition, while keratoprosthesis offers vision to patients who are poor candidates for traditional keratoplasty, infectious complications can be severe and sight threatening. Although antimicrobials remain the mainstay of treatment, definitive management often requires surgical intervention.

Long-term safety and efficacy of high-fluence collagen crosslinking of the vehicle cornea in Boston keratoprosthesis type 1

PURPOSE

The aim of this study was to evaluate the safety and efficacy of very high-fluence collagen crosslinking (CXL) as a means of achieving increased corneal rigidity and reduced enzymatic digestion in the vehicle cornea of Boston keratoprosthesis (KPro) type 1.

METHODS

Eleven consecutive patients fitted with a KPro (5 with a previous repeat cornea graft failure, 4 with ocular cicatricial pemphigoid, and 2 with chemical burn) underwent donor vehicle cornea pretreatment with very high-fluence prophylactic CXL in a 2-step procedure. First, the donor cornea was crosslinked with an intrastromal riboflavin instillation through a femtosecond laser-created pocket. This was followed up with a superficial CXL treatment. On the completion of the CXL pretreatment, the cornea center was trephined with the femtosecond laser, and the KPro was fitted onto the crosslinked donor cornea. Visual acuity, corneal surface, and donor vehicle cornea stability were evaluated. Follow-up evaluations were conducted over the next 9 years with a mean of 7.5 years.

RESULTS

Mean uncorrected visual acuity improved from light perception to 20/60. One patient required a follow-up surgery, because of significant melt in the host cornea. None of the eyes developed melts and/or infection, especially on the vehicle cornea on which the KPro was fitted.

CONCLUSIONS

Pretreatment with intrastromal and superficial very high-fluence CXL in conjunction with Boston type 1 KPro seems to be a safe and effective adjunctive treatment for achieving increased vehicle donor cornea rigidity. Additionally, there is an increased resistance to enzymatic degradation. This application may serve to enhance the biomechanical stability and external disease resistance of the donor vehicle cornea in patients with advanced external disease.

A year of cornea in review: 2013

PURPOSE

The goal of this study was to provide an update of significant corneal literature published in 2013.

DESIGN

This study is a systematic literature review.

METHODS

We conducted a systematic review of the English-language literature published from January 1, 2013, to December 31, 2013, using the following PubMed search and Medical Subject Headings terms: cornea transplantation, keratoplasty, Descemet membrane endothelial keratoplasty, Descemet stripping endothelial keratoplasty, cross linking, pre-Descemet's layer, Rho-associated kinase, keratoprosthesis, infectious keratitis, corneal dystrophy, corneal astigmatism, and keratoconus.

RESULTS

This review summarizes relevant and innovative original articles, review articles, and novel techniques from the following journals: American Journal of Ophthalmology, British Journal of Ophthalmology, Cornea, Graefe's Archive for Clinical and Experimental Ophthalmology, Investigative Ophthalmology & Visual Science, JAMA Ophthalmology, Journal of Cataract and Refractive Surgery, Journal of Refractive Surgery, and Ophthalmology. Case reports, abstracts, letters to the Editor, and unpublished work were excluded, as well as articles e-published ahead of print in 2012 that were discussed in the previous review. One hundred twenty-seven articles met the criteria for this review.

CONCLUSIONS

This review summarizes significant cornea-related literature from 2013.

Characteristics and management of patients with Boston type 1 keratoprosthesis explantation--the University of Montreal Hospital Center experience

PURPOSE

To describe the characteristics of patients who had Boston keratoprosthesis (KPro) explantation and the outcomes of their subsequent management.

DESIGN

Retrospective observational study.

METHODS

Cases that underwent Boston type 1 KPro at University of Montreal Hospital Center between October 2008 and May 2012 were reviewed. Patients with KPro explantation were identified and compared to those with KPro retention. Visual acuity, expressed as logMAR, was followed as primary outcome.

RESULTS

A total of 345.1 life-years of device implantation were included in the analysis. Among 110 operated eyes, 11 eyes had KPro explantation, corresponding to a failure rate of 0.03/life-year. KPro was explanted at 19.7 ± 10.5 (4-40) months post KPro. Indications included sterile keratolysis (n = 7), infection (n = 2), and hypotony and painful blind eye (1 each). Compared to patients with KPro retention, those requiring KPro explantation were associated with aniridia (P = .0038), sterile keratolysis (P < .001), retroprosthesis membrane (P = .02), and intraocular inflammation (P = .04). KPro exchange (n = 8), penetrating keratoplasty (n = 1), or evisceration (n = 2) were performed as a secondary intervention. Among patients with KPro explantation, 4 (36.4%) recovered better than baseline visual acuity at final visit. Posterior segment complications (n = 5, 62.5%) were the most common cause of permanent vision loss. Final visual prognosis correlates with pre-explantation visual function (r = 0.68, P = .02).

CONCLUSIONS

Boston KPro explantation is a serious complication. Aniridic eyes are at significant risk and have a shortened keratoprosthesis retention time. When managed appropriately, patients can recover significant vision.

Experience with Boston keratoprosthesis type 1 in the developing world

OBJECTIVE

To report the experience of the Federal University of São Paulo, Brazil, in performing Boston keratoprosthesis type 1 implantation in the developing world.

METHODS

We analyzed 30 eyes of 30 patients who underwent Boston type 1 keratoprosthesis surgery between 2008 and 2012 in a prospective interventional study. Preoperative, perioperative, and postoperative parameters were analyzed, including visual acuity (VA), keratoprosthesis stability, and postoperative complications.

RESULTS

Preoperative diagnoses were failed grafts in 16 eyes (53.33%), chemical injury in 10 eyes (33.33%) and Stevens-Johnson syndrome in 4 eyes (13.33%). Also, 16 eyes (53.33%) had preoperative glaucoma. Preoperative best corrected VA ranged from 20/400 to light perception. With an average follow-up of 32 months (range 1-55 months), postoperative vision improved to >20/200 in 24 eyes (80%). Postoperative VA was statistically improved compared with the preoperative measurement during all postoperative follow-ups (up to 36 months). During the follow-up period (32 months), retention of the initial keratoprosthesis was 93.3%. The incidence of retroprosthetic membrane was 26.66%. Progression of glaucoma occurred in 7 of 16 eyes (43%). Three patients experienced development of glaucoma after keratoprosthesis implantation. One eye experienced development of infectious keratitis, and 2 eyes had retinal detachment.

CONCLUSIONS

Performing Boston type 1 keratoprosthesis in a developing country is a viable option after multiple keratoplasty failures and conditions with a poor prognosis for keratoplasty. Our experience appears similar to major reports in the field from investigators in developed countries. Adjustments to postoperative management must be considered according to the particular location.