Infectious keratitis after keratoplasty

Unveiling the landscape of post-keratoplasty keratitis: a comprehensive epidemiological analysis in a tertiary center

PURPOSE

The present study aimed to epidemiologically evaluate patients with infectious keratitis following corneal transplantation.

METHODS

This retrospective study analyzed medical records of patients who underwent keratoplasty from March 2014 to March 2022 at a tertiary center. A total of seventy-five patients were evaluated. The data were classified based on culture results, the type of microorganisms involved, treatment requirements, and the type of primary keratoplasty performed.

RESULTS

Seventy-five patients were evaluated in this study, with a mean age of 45.9 years (22-95 years). The mean duration between the first surgery and the incidence of infectious keratitis was 1.43 years, and most cases occurred in the first year (56.2%). Bacterial and fungal keratitis in 2.17%, 1.39%, and 1.26% of cases undergoing penetrating keratoplasty (PK), endothelial keratoplasty (EK), and anterior lamellar keratoplasty (ALK) occurred, respectively. Streptococcus viridans (9.3%) and Staphylococcus aureus (6.6%) had the highest prevalence. Across various smear and culture results (gram-positive, gram-negative, fungal, and negative culture), no significant differences were found in endophthalmitis rates (P = 0.797) and the necessity for tectonic grafts (P = 0.790). Similarly, the choice of surgical method (PK, ALK, EK) showed no significant impact on the need for tectonic grafts (P = 0.45) or the rate of endophthalmitis (P = 0.55).

CONCLUSIONS

The incidence of keratitis after a corneal graft was 1.7%, with Streptococcus viridans and Staphylococcus aureus the most common microorganisms. The rate of endophthalmitis associated with post-keratoplasty keratitis was 0.053%. There was no correlation between the necessity for a tectonic graft or the incidence of endophthalmitis and the type of microorganisms involved.

Post-Keratoplasty Microbial Keratitis in the Era of Lamellar Transplants-A Comprehensive Review

Microbial keratitis in a post-transplant cornea should be considered a distinct entity from microbial keratitis in a non-transplant cornea. Firstly, the use of immunosuppressive treatments and sutures in corneal transplants changes the etiology of keratitis. Secondly, corneal transplant has an impact on corneal biomechanics and structure, which facilitates the spread of infection. Finally, the emergence of lamellar transplants has introduced a new form of keratitis known as interface keratitis. Given these factors, there is a clear need to update our understanding of and management strategies for microbial keratitis following corneal transplantation, especially in the era of lamellar transplants. To address this, a comprehensive review is provided, covering the incidence, risk factors, causes, and timing of microbial keratitis, as well as both clinical and surgical management approaches for its treatment in cases of penetrating and lamellar corneal transplants.

Infectious Keratitis After Keratoplasty in the United States: Analysis of a National Medicare Claims Data Set

PURPOSE

The aim of this study was to assess the incidence, trends, and risk factors of infectious keratitis (IK) and subsequent repeat keratoplasty after penetrating keratoplasty (PK) and endothelial keratoplasty (EK).

METHODS

Using a retrospective cohort study design, IK cases within 6 months of keratoplasty were identified using billing codes among 100% Medicare beneficiaries aged 65 years and older who underwent either PK or EK between 2011 and 2020. Multivariable logistic regression models were used to evaluate factors associated with postkeratoplasty IK.

RESULTS

We identified 115,588 keratoplasties, of which 20.0% (n = 23,144) were PK and 80.0% (n = 92,444) were EK. IK developed within 6 months with a rate of 3.32% (n = 769) post-PK and 0.72% (n = 666) post-EK. Overall rates of IK decreased from 16.05 to 9.61 per 1000 keratoplasties between 2011 and 2020 ( P < 0.001). The median interval between keratoplasty and diagnosis of IK was 73 days (interquartile range: 29-114 days) for PK and 74 days (interquartile range: 38-116 days) for EK. After IK, 22.9% (n = 176) and 23.8% (n = 159) eyes underwent repeat keratoplasty within 1 year for PK and EK, respectively. The occurrence of IK after PK was associated with age 85 years and older [odds ratio (OR): 1.38; 95% confidence interval (CI): 1.13-1.68] relative to patients aged 65 to 74 years. The occurrence of IK after EK was also associated with age 85 years and older (OR: 1.44; 95% CI: 1.14-1.82) relative to patients aged 65 to 74 years.

CONCLUSIONS

IK was 4 times more common after PK than EK and the complication was associated with older age. Our findings may help corneal surgeons in counseling patients at higher risk and guiding their postoperative care.

Factors Associated With Laboratory Test Negativity Following a Transition in Specimen Collection in Microbial Keratitis Cases

PURPOSE

Negative laboratory results make targeting microbial keratitis treatment difficult. We investigated factors associated with laboratory negativity in patients with microbial keratitis in the context of a transition to a new specimen collection method.

METHODS

Microbial keratitis patients with associated laboratory tests were identified in the electronic health record of a tertiary care facility from August 2012 to April 2022. Patient demographics and laboratory results were obtained. Random sampling of 50% of charts was performed to assess the impact of the ocular history and pretreatment measures. The relationship between probability of negative laboratory results with demographics, ocular history, pretreatment measures, and utilization of a new specimen collection method (i.e. ESwab) was evaluated by multivariable logistic regression.

RESULTS

Of 3395 microbial keratitis patients identified, 31% (n = 1051) had laboratory tests. Laboratory testing increased over time (slope = 2.5% per year, p < 0.001; 19.6% in 2013 to 42.2% in 2021). Laboratory negative rate increased over time (slope = 2.2% per year, p = 0.022; 48.5% in 2013 to 62.3% in 2021). Almost one-third of patients (31.2%, n = 164) were pretreated with steroids. Over two-thirds of patients were pretreated with antibiotics (69.5%, n = 367). 56.5% (n = 297) of patients were outside referrals. In multivariable regression, patients with corticosteroid pretreatment had lower odds of negative laboratory results (odds ratio [OR] = 0.49, p = 0.001). There were higher odds of negative laboratory results for every additional antibiotic prescribed to a patient prior to presentation (OR = 1.30, p = 0.006) and for specimens collected using ESwabs (OR = 1.69, p = 0.005). Age, prior eye trauma, outside referrals, and contact lens wear were not significantly associated with negative laboratory results.

CONCLUSION

More microbial keratitis associated laboratory tests are being taken over time. Over 60% of tests were negative by 2022. Factors associated with negative laboratory test results included pretreatment with antibiotics and specimens collected with the new collection method.

Synergistic activity of clioquinol with voriconazole and amphotericin B against fungi of interest in eye infections

Keratoplasty represents a risk factor for fungal eye infections, despites the antibacterial actives in the corneal tissue preservation means, it does not contain active substances with antifungal action. Among the most commonly associated fungal agents are the species belonging to the genera Fusarium and Candida. These agents can trigger an infectious process characterized by swift progression associated with high rates of morbidity, causing irreversible damage. Polyene and azole antifungals are the main agents of ocular therapy, however, they demonstrate some limitations, such as their toxicity and fungal resistance. In this context, drug repositioning and the combination of antifungals may be an alternative. Hence, the goal of this study was to investigate the potential activity of clioquinol (CLQ), a derivative of 8-hydroxyquinoline with previously described antifungal activity, along with its triple and quadruple combinations with antifungal agents commonly used in ophthalmic fungal therapy, natamycin (NAT), voriconazole (VRC), and amphotericin B (AMB), against main fungal pathogens in eye infections. The MICs for CLQ ranged from 0.25 to 2.0 μg/mL, for NAT from 4.0 to 32.0 μg/mL, for AMB it ranged from 0.25 to 16.0 μg/mL and for VRC from 0.03125 to 512.0 µg/mL. Among the tested combinations, the VRC-AMB-CLQ combination stands out, which showed a synergistic effect for more than 50 % of the tested strains and did not present antagonistic results against any of them. Toxicity data were similar to those antifungals already used, even with lower potential toxicity. Therefore, both clioquinol and the triple combination VCR-AMB-CLQ exhibited promising profiles for use as active components in corneal tissue preservation medium.

Application of biomaterials and nanotechnology in corneal tissue engineering

Corneal diseases are among the most common causes of blindness worldwide. Regardless of the etiology, corneal opacity- or globe integrity-threatening conditions may necessitate corneal replacement procedures. Several procedure types are currently available to address these issues, based on the complexity and extent of injury. Corneal allograft or keratoplasty is considered to be first-line treatment in many cases. However, a significant proportion of the world's population are reported to have no access to this option due to limitations in donor preparation. Thus, providing an appropriate, safe, and efficient synthetic implant (e.g., artificial cornea) may revolutionize this field. Nanotechnology, with its potential applications, has garnered a lot of recent attention in this area, however, there is seemingly a long way to go. This narrative review provides a brief overview of the therapeutic interventions for corneal pathologies, followed by a summary of current biomaterials used in corneal regeneration and a discussion of the nanotechnologies that can aid in the production of superior implants.

Atypical microbial keratitis

Atypical microbial keratitis refers to corneal infections caused by micro-organisms not commonly encountered in clinical practice. Unlike infections caused by common bacteria, cases of atypical microbial keratitis are often associated with worse clinical outcomes and visual prognosis. This is due to the challenges in the identification of causative organisms with standard diagnostic techniques, resulting in delays in the initiation of appropriate therapies. Furthermore, due to the comparatively lower incidence of atypical microbial keratitis, there is limited literature on effective management strategies for some of these difficult to manage corneal infections. This review highlights the current management and available evidence of atypical microbial keratitis, focusing on atypical mycobacteria keratitis, nocardia keratitis, achromobacter keratitis, and pythium keratitis. It will also describe the management of two uncommonly encountered conditions, infectious crystalline keratopathy and post-refractive infectious keratitis. This review can be used as a guide for clinicians managing patients with such challenging corneal infections.

Citrobacter keratitis: predisposing factors and clinical characteristics

PURPOSE

To report predisposing factors, clinical presentation, antibiotic sensitivity, and management of Citrobacter-caused infectious keratitis.

METHODS

We retrospectively reviewed the medical records of culture-proven cases of Citrobacter keratitis in a tertiary referral center for 8 years (from January 2012 to September 2020). Demographic data of the patients, predisposing factors, and presenting signs were extracted.

RESULTS

Eighteen cases of microbial keratitis due to Citrobacter spp. were identified. The median age of the patients was 66 years (range: 10-89, interquartile range : 59-81). Thirteen patients were male and 5 were female. Multiple predisposing factors were identified in all eyes, including ocular surface disease (n = 8), previous corneal surgery (n = 6), and history of ocular trauma (n = 6). Five patients were diabetic. Corrected distance visual acuity (CDVA) of patients was light perception (LP) in 8 patients, hand motion (HM) in 7, counting fingers (CF) at 1 m in 1, and CF at 2 m in 2 patients. Thirteen eyes exhibited hypopyon. An area of corneal thinning was observed in 7 eyes (38.9%). Endophthalmitis due to infectious keratitis developed in one patient. In vitro susceptibility testing confirmed high sensitivity to ceftazidime and aminoglycosides. Medical management consisted primarily of topical amikacin (20 mg/ml) combined with topical cefazoline (50 mg/ml) (72.2%). Surgical tectonic procedures were carried out in 7 eyes (38.9%).

CONCLUSION

Citrobacter spp. is a rare cause of bacterial keratitis.Previous keratoplasty and ocular surface problems are important risk factors. The prognosis is not good and surgical tectonic intervention is required in many cases to resolve the corneal infection.

Clinical outcomes of Descemet membrane endothelial keratoplasty performed in eyes with keratoconus and corneal endothelial dysfunction

PURPOSE

To evaluate the clinical outcome of Descemet membrane endothelial keratoplasty (DMEK) performed in eyes with comorbid keratoconus (KCN) and corneal endothelial dysfunction.

METHODS

Twenty-five consecutive eyes of 14 patients with comorbid stable KCN underwent DMEK for corneal endothelial dysfunction; best spectacle corrected visual acuity (BSCVA), maximum corneal curvature (Kmax), maximum corneal power (Pmax), central corneal thickness (CCT), and intra- and postoperative complications were assessed.

RESULTS

Excluding eyes requiring re-transplantation for primary graft failure (n = 3), all eyes showed improvement in BSCVA, reaching ≥ 20/40 (0.5) in 86%, ≥ 20/25 (0.8) in 55%, and ≥ 20/20 (1.0) in 27% by one month postoperatively; 90%, 76%, and 48% by 6 months postoperatively; and 88%, 76%, and 47% by 12 months postoperatively. CCT decreased from 571μm preoperatively to 485μm at 1 month (p < 0.001) and 481μm at 12 months (p < 0.001). Kmax decreased by a median of 1.4 diopters (D) at 1 month (p = 0.003) and 3.1 D at 12 months (p = 0.021), and every eye with a preoperative Kmax ≥ 46 D demonstrated flattening. Pmax decreased by 2.1 D at 1 month (p = 0.001) and 4.0 D at 12 months (p = 0.016).

CONCLUSION

DMEK is technically feasible in eyes with comorbid KCN and may give excellent outcomes visual and refractive outcomes, including significant corneal flattening, which may potentially create a visually significant hyperopic shift in patients with severely ectatic corneas.

Enterobacter cloacae Keratitis: Clinicomicrobiological Profiles, Risk Factors, and Outcomes

PURPOSE

The purpose of the study was to report the clinical features, risk factors, antibiotic susceptibility, and treatment outcomes in a series of Enterobacter cloacae keratitis.

METHODS

A retrospective analysis was performed of the electronic medical records of microbial keratitis caused by E. cloacae identified by the Vitek 2 system (BioMerieux, Craponne, France). We collected data pertaining to demographics, risk factors, ulcer characteristics, antibiogram, visual acuity at presentation and final follow-up, and management outcome. The main outcome measure was resolution of infection. The final visual acuity was the secondary outcome measure.

RESULTS

Ten episodes of E. cloacae keratitis in 9 patients were identified between January 2009 and December 2019. Nine (90%) cases had undergone penetrating keratoplasty and 8 were failed grafts. Other risk factors included topical steroid use and irregular ocular surface due to epithelial bullae. The mean ulcer size was 17.55 ± 13.99 mm 2 . More than 80% of isolates were sensitive to chloramphenicol, gentamicin, and colistin. Nine (90%) cases healed on medical management within 56.55 ± 26.74 days (range 9-120 d), although almost all required adjunctive procedures: tissue adhesive application (n = 6) and/or tarsorrhaphy (n = 4). One case with a near total infiltrate had a mixed infection with Kocuria kristinae requiring therapeutic penetrating keratoplasty. One case developed endophthalmitis and phthisis after the corneal infiltrate resolved.

CONCLUSIONS

E. cloacae keratitis is a rare clinical entity seen more often in immunocompromised host conditions such as failed corneal transplants with concomitant topical steroids. Most cases healed with medical management.

Ocular emergencies visits after corneal transplantation at a tertiary eye care hospital in Saudi Arabia

PURPOSE

To evaluate the characteristics of patients with post-keratoplasty complications and their presentation at an emergency center.

DESIGN

Retrospective one-armed cohort study.

METHODS

Data were evaluated on patients who underwent corneal grafts in 2019 and presented to an emergency unit. Data were collected on patient demographics, presenting symptoms, clinical details, diagnosis at emergency visit, final diagnosis, best-corrected visual acuity (BCVA) at presentation and at the last follow-up after management. Severe visual impairment (SVI) and graft rejection were tested for correlations to other factors.

RESULTS

The study sample was comprised of 149 eyes of 124 patients with a mean age of 27.5 years. Keratoconus was the indication for keratoplasty in 94 (75.8%) patients. The main presenting symptoms were pain 57 (38.3%) and red eye in 52 (34.9%) patients. The median interval between emergency visit and keratoplasty was 1.6 years. There were 63 (42.3%) patients who had emergency visits due to suture-related problems. The rates of SVI and graft rejection at the time of discharge after managing emergencies in eyes with previous keratoplasty were 14.1% (95% CI 8.5; 19.7) and 13.4 (95% CI 7.9; 18.9), respectively. Keratoconus (OR = 22.8) and young age (P < 0.001) were negatively associated with SVI after management.

CONCLUSION

Patients with keratoplasty are at high risk for severe vision loss and should be counseled to seek urgent eye care for early detection and management of sight-threatening complications to improve graft survival and vision.

The treatment of end-stage corneal disease: penetrating keratoplasty compared with Boston type 1 keratoprosthesis

Penetrating keratoplasty (PKP) yields excellent results for restoring vision in end-stage corneal diseases. However, its success is limited to high-risk diseases such as aniridia, chemical burns, autoimmune corneal diseases, and herpetic eye disease. Boston type 1 keratoprosthesis (BKPro) offers another option to these patients. Since 1992, improvements in perioperative management and device construction have significantly increased the use of BKPro worldwide and challenged the therapeutic role of PKP in these patients. This review aims to evaluate BKPro's place in the treatment algorithm of these high-risk patients to assist surgeons' decision-making. PKP and BKPro are compared in three outcome categories: visual acuity, graft retention and failure, and complications profile. Special attention is given to comparing secondary BKPro versus repeated PKP as well as primary BKPro versus primary PKP. We conclude that secondary BKPro bears a better prognosis than repeated PKP in most high-risk patients. Similarly, primary BKPro likely confers improved outcomes over primary PKP in most high-risk recipients. However, current evidence is based on retrospective designs, and controlled prospective randomized trials are required to validate these conclusions.

Keratitis following descemet's stripping endothelial keratoplasty (DSEK): Clinical features and outcome in early vs late presentation

OBJECTIVE

To compare the clinical presentation, risk factors, causative organisms, and final outcome of early- and late- onset microbial keratitis following Descemet's Stripping Endothelial Keratoplasty (DSEK).

MATERIALS AND METHODS

In a retrospective, comparative, case series, twenty-three (10 early-onset keratitis, 13 late-onset keratitis) cases were included for analysis from a single centre tertiary eye care setup. Data about demography, indication, clinical features, and outcome were collected for both the groups. Comparison of clinical presentation, risk factors, microbiology and final outcome were carried out.

RESULTS

The most common indication was failed graft. While all patients with late-onset keratitis presented with ulcerative keratitis, 60% of early-onset keratitis presented with ulcerative keratitis. Four patients in the early-onset group had interface keratitis. Associated endophthalmitis was more in the early-onset compared to the late-onset group. Early-onset interface keratitis cases are mostly associated with donor-related infection. Gram-positive bacteria were the most common organisms isolated from both early- and late- onset infection. Major surgical procedures in both early- and late- onset keratitis included lenticule removal (n = 4) and therapeutic penetrating keratoplasty (n = 5).

CONCLUSIONS

Failed graft is a major risk factor in post-DSEK keratitis. Interface keratitis and endophthalmitis are commonly observed in early-onset keratitis. A majority of the patients need surgical intervention.

Post penetrating keratoplasty infectious keratitis: Clinico-microbiological profile and predictors of outcome

PURPOSE

To study the clinico-microbiological profile, outcomes and prognostic factors of post penetrating keratoplasty (PKP) infectious keratitis.

METHODS

Retrospective review of medical records of 78 patients with post PKP infectious keratitis presenting between January 2014 and December 2018. Demographic, clinical and microbiological profile was documented and predictors of treatment and graft success were evaluated using univariate and subsequent multivariate logistic regression analysis.

RESULTS

Mean age of patients was 52.17 ± 15.51 years and mean infiltrate size was 19.39 ± 19.68 mm². Mean duration of presentation with infection post PKP was 11.66 ± 10.65 months. Culture positivity was seen in 64 eyes (82.05%). Bacterial growth was observed in 47 eyes (60.25%), fungal growth in 17 (21.79%) and no microbiological growth in 14 eyes (17.94%). At 3 months the visual acuity (VA) improved in 37 eyes (47.44%), did not change in 27 (34.62%) and deteriorated in 14 (17.95%). Graft failure was noted in 53 eyes (73.08%). Surgical intervention was needed in 47 (60.25%) eyes of which most common was therapeutic PKP in 32 eyes (41.02%). Treatment failure was noted with fungal infection (p = 0.05), poorer vision at presentation (p = 0.02), larger infiltrate area (p = 0.002) and graft infection developing before 1 year (p = 0.02). Graft failure was noted with associated endophthalmitis (p = 0.02), poorer VA at presentation (p = 0.01) and larger infiltrate area (p = 0.02).

CONCLUSION

Post PKP infectious keratitis is a sight threatening ocular condition. It is associated with high incidence of graft failure and frequently requires surgical intervention. Fungal etiology, larger infiltrate size, poorer vision at presentation and associated endophthalmitis carries a poorer prognosis.

Comparison of Clinical Features and Treatment Outcomes of Pseudomonas aeruginosa Keratitis in Contact Lens and Non-Contact Lens Wearers

PURPOSE

To compare the outcomes of Pseudomonas aeruginosa keratitis (PAK) in contact lens wearers (CLWs) and non-contact lens wearers (non-CLWs) and identify risk factors for poor visual acuity (VA) outcomes in each group.

DESIGN

Retrospective cohort study METHODS: Two hundred fourteen consecutive cases of PAK were included between January 2006 and December 2019. Clinical features, microbiologic results, and treatment course were compared between CLW and non-CLW groups. Analyses of clinical features predicting poor final VA were performed.

RESULTS

This study identified 214 infected eyes in 207 patients with PAK, including 163 eyes (76.2%) in CLWs and 51 eyes (23.8%) in non-CLWs. The average age was 39.2 years in CLWs and 71.9 years in non-CLWs (P < .0001). The average logMAR visual acuity (VA) at presentation was 1.39 in CLWs and 2.17 in non-CLWs (P < .0001); average final VA was 0.76 in CLWs and 1.82 in non-CLWs (P < .0001). Stromal necrosis required a procedural or surgical intervention in 13.5% of CLWs and 49.0% of non-CLWs (P < .0001). A machine learning-based analysis yielded a list of clinical features that most strongly predict a poor VA outcome (worse than 20/40), including worse initial VA, older age, larger size of infiltrate or epithelial defect at presentation, and greater maximal depth of stromal necrosis.

CONCLUSIONS

Non-CLWs have significantly worse VA outcomes and required a higher rate of surgical intervention, compared with CLWs. Our study elucidates risk factors for poor visual outcomes in non-CLWs with PAK.

Early postoperative infection following lamellar keratoplasty: a review

With the growing popularity of lamellar keratoplasty for selective replacement of diseased corneal tissue, it is important to understand the risk of developing an infection after the procedure. Although lesser than that postpenetrating keratoplasty, the reports on post lamellar keratoplasty infectious keratitis are not negligible. Trends of acute infections arising within 2 months of surgery are a subject of interest. Most of these infections are reported post Descemet's stripping endothelial keratoplasty with a preponderance of Candida species. A donor to host transmission of infection is not uncommon. Among the Candida cases, about 80% seem to occur due to a donor to host transmission. Infections presenting as or progressing to endophthalmitis lead to a poor visual outcome. Strict aseptic measures and protocols during corneal tissue harvesting, tissue processing, tissue storage and surgery are essential to prevent occurrence of these infections. After the infection has occurred, determining the aetiology and drug susceptibility through microbiological testing is vital. This helps to guide treatment protocols and hence determines final outcome of these cases. Most cases require some form of surgical management for resolution of infection, most often a graft removal and therapeutic keratoplasty. Secondary surgical interventions are performed to restore graft clarity and achieve a good final visual outcome.

Usefulness of Prestorage Corneal Swab Culture in the Prevention of Contaminated Corneal Tissue in Corneal Transplantation

PURPOSE

To assess the efficacy of the prestorage corneal swab (PCS) culture to screen for corneal graft contamination after storage in Optisol-GS.

METHODS

A retrospective analysis of all PCS cultures was performed at the Eye Bank of Québec in Hôpital Maisonneuve-Rosemont from September 2013 to June 2016. Whole corneal culture was performed on rejected grafts because of a positive PCS, and a contamination rate was calculated. In addition, contamination rates of corneoscleral rims were compared between corneas tested with PCS and those of imported corneas which did not have PCS.

RESULTS

Among the 1966 PCS cultures performed, 814 (41.4%) were positive for growth. Pathogenic bacteria were present in 144 (7.3%) corneas, including Staphylococcus aureus (n = 96, 11.8% of all positive cultures), Enterobacteriaceae (n = 14, 1.7%), and Pseudomonas aeruginosa (n = 6, 0.7%). After preservation in Optisol-GS, only 7 (6.9%) corneas remained contaminated (95% confidence interval 5.1-9.3). The sensitivity of the PCS culture was 87.5% (95% confidence interval 47.4-99.7). There was no significant difference in corneoscleral rim contamination between corneas tested with PCS (1/388; 0.2%) compared with imported, nonswabbed corneas (3/214; 1.4%) (P = 0.131). Therefore, the cost to recover the loss of tissue rejected because of false-positive PCS by purchasing corneal tissue was calculated to be $142,884 (CAD) per year.

CONCLUSIONS

Despite the high sensitivity of PCS cultures, there was no significant reduction of infection after corneal transplantation using this technique. In consequence, 93% of the corneas possibly suitable for transplantation were rejected. This suggests that the PCS culture alone is a poor test for detecting clinically relevant corneal contamination.

Infectious keratitis after lamellar keratoplasty

Infectious keratitis after lamellar keratoplasty is a potentially devastating complication that may severely limit the visual and anatomical outcomes. The deep-seated location of the infiltrates, sequestration of the pathogenic microorganisms and limited penetration of the currently available antimicrobial agents often results in delayed diagnosis that may jeopardize the management in these cases. Fungal keratitis is more common as compared with bacterial or viral keratitis and classically presents as white interface infiltrates that may not be associated with significant inflammation. Confocal microscopy may help to establish a rapid diagnosis in such cases, and anterior segment optical coherence tomography may be used to determine the extent of infection and monitor its progression. Conservative measures such as topical antimicrobials and interface irrigation with antimicrobial agents may be done. Surgical intervention in the form of partial excision/removal of the graft in endothelial keratoplasty or a full-thickness keratoplasty is often required for the effective management of deep-seated infections. Timely diagnosis and intervention may result in complete resolution of infection in both anterior lamellar and endothelial keratoplasty. Infections after anterior lamellar keratoplasty have a fair prognosis, and a clear graft with functional visual acuity may be achieved in most cases. By contrast, infections after endothelial keratoplasty have a guarded prognosis, and the presence of concomitant endophthalmitis may further complicate the graft survival and visual outcomes.

Microbial keratitis and clinical outcomes following penetrating and endothelial keratoplasty

PURPOSE

The goal of this study was to review the incidence, risk factors and outcomes of microbial keratitis after penetrating keratoplasty (PK) and endothelial keratoplasty (EK).

METHODS

The electronic medical records at Wills Eye Hospital were queried for cases of microbial keratitis following PK or EK performed between 1 May 2007 and 1 September 2018. Charts were reviewed to obtain demographic data, transplant characteristics, details of microbial keratitis, graft survival and clinical outcomes.

RESULTS

During the study period, 2098 transplants were performed in 1601 patients. Of these, 1267 (60.4%) were PKs and 831 (39.6%) were EKs. We identified 86 (4.1%) cases of subsequent microbial keratitis. The incidence of microbial keratitis after PK was significantly higher than after EK (5.9% versus 1.3%; p = 0.005). Furthermore, the rate of infection was higher after repeat transplants (either PK or EK) compared to initial keratoplasties (5.5% versus 3.4%; p = 0.02). Twenty-six (32.1%) grafts remained clear at most recent follow-up after microbial keratitis, and the proportion of clear grafts was higher after EK than PK (66.7% versus 27.8%; p = 0.03).

CONCLUSION

Rates of microbial keratitis were significantly higher after PK compared to EK, and repeat transplantation was a risk factor for microbial keratitis. To the best of our knowledge, there is no prior study in the literature evaluating microbial keratitis rates after PK and EK and comparing outcomes.

Distribution of Microbial Keratitis After Penetrating Keratoplasty According to Early and Late Postoperative Periods

Objectives:

The aim of this study was to investigate the distribution of microbial agents in the early and late postoperative periods in patients with microbial keratitis (MK) after penetrating keratoplasty (PK).

Materials and Methods:

The records of 36 patients who were clinically diagnosed as having MK after PK were retrospectively reviewed. Culture results were obtained from microbiology records and the organisms that were produced were noted. A case was deemed as viral keratitis based on the clinical appearance, negative cultures, and response to antiviral treatment. Keratitis development times were evaluated in 2 categories: early (within the first year) and late (after year 1) postoperative period. Mann-Whitney U and Kruskal-Wallis tests were used to compare numerical variables that did not show normal distribution and chi-square test was used to compare categorical variables.

Results:

The majority of MK cases were of bacterial origin (55.5%, n=20), followed by viral (41.7%, n=15) and fungal (2.8%, n=1). Of the 15 cases of early postoperative MK, 10 were bacterial, 4 were viral, and 1 was fungal; however, among cases of late postoperative MK, 10 were bacterial and 11 were viral. The majority (65%) of early and late bacterial infections were caused by gram-positive strains (most commonly staphylococci). Gram-positive bacteria caused keratitis significantly earlier than gram-negative bacteria (p=0.037). Viral and gram-negative bacterial MK was more frequent in the late postoperative period, but the difference was not statistically significant.

Conclusion:

In our study, bacterial keratitis was more common in post-keratoplasty MK than viral and fungal keratitis. Gram-positive bacteria were the most common causative agents. The increased incidence of gram-negative bacterial agents and viral keratitis in the late postoperative period can be explained by long-term topical steroid use.

Corneal graft failure: an update

Corneal graft surgery is one of the most successful forms of human solid-tissue transplantation, and nowadays, there is a worldwide expansion of the surgical volume of corneal grafts. This surgery is continuously evolving, with new surgical techniques and postoperative treatments that have considerably increased the chance of survival for the grafts. Despite the high rate of success, corneal transplantation is still complicated by a relevant risk of graft failure. This study investigates the causes that lead to the failure of the different corneal graft surgical techniques and provides an updated synthesis on this topic. A comprehensive review of the main pathological pathways that determine the failure of corneal grafts is provided, analysing the main risk factors and disclosing the survival rates of the principal form of corneal grafts. Our results revealed that penetrating keratoplasty has higher failure rates than lamellar keratoplasty, with immunological rejection being the leading cause of graft failure, followed by late endothelial failure (LEF) and ocular surface disorders. Postoperative glaucoma and dehiscence of the surgical wound represent other important causes of failure. Endothelial keratoplasty showed the lowest rates of failure in the mid-term, with LEF, detachment of the graft and primary graft failure representing the most common pathological reasons for failure.

Comparison of the Clinical Efficacy of Boston Keratoprosthesis Type I and Repetitive Penetrating Keratoplasty for Refractory Keratopathy

OBJECTIVE

To compare the clinical efficacy of Boston Keratoprosthesis type I (B-KProI) and penetrating keratoplasty (PKP) for patients with refractory keratopathy after 1failed PKP in China.

METHOD

The 42 consecutive cases with refractory keratopathy after 1 failed PKP, from July 2010 to December 2014, were divided into 2 groups according to the surgical method: KPro group (n = 21) and PKP group (n = 21). Visual acuity (LogMAR), corneal graft transparency, postoperative complications and corneal graft survival rate were observed. The follow-up time was 2 years. The Kaplan-Meier curve was used to analyze the survival rate of the two groups of corneal grafts.

RESULTS

The average best corrected visual acuity (BCVA) at 1, 6, 12, 18, and 24 months in KPro group were significantly lower than PKP group (P < 0.01). The best postoperative visual acuity and BCVA at postoperative 2 years in KPro group were lower than PKP group. The success rate of KPro group (86%) were significantly higher than PKP group (43%) (P < 0.01). There were no significant differences in indicate of complications in 2 groups including secondary glaucoma, secondary infectious corneal ulcer, corneal graft melting and endophthalmitis (P > 0.05).

CONCLUSION

Compared with repetitive PKP, B-KProI had a higher success rate, improved postoperative visual acuity, reduced postoperative corneal transplant rejection rates and improved corneal graft survival rate.

Corneal graft melting: a systematic review

Corneal graft melting is a severe complication of keratoplasty. This review is to summarize the incidence, the pathogenesis, the risk factors, the prognosis and the prevention of corneal graft melting after keratoplasty. We systematically searched PubMed, Web of Science and WanFang database to retrieve potentially eligible articles about relevant clinical reports and animal experiments. We read the full texts to identify eligible articles. The selection of studies and data extraction were performed independently by two reviewers. In conclusion, the pathogenesis of corneal graft melting is complicated, and many risk factors are closely related to corneal graft melting. Analysis of pathogenesis and risk factors of corneal graft melting can facilitate the development of targeted therapies to better guide clinical practice.

Microbiological contamination in donor corneas preserved for medium-term

To evaluate the characteristics of microbiological contamination in donor corneas preserved for medium-term. A total of 82 donated corneas from June 1, 2014 to November 30, 2014 were retrospectively analyzed. The corneas were preserved in cornea chambers medium-term solution at 4-8 °C for keratoplasty. After removal of the central corneas for transplantation, the corneoscleral rims were put back into the medium for 1 month at room temperature (20-25 °C). The suspicious contaminated storage solutions indicated with transparency or color change were examined with bacteria and fungi cultivation for strain identification. The data collected included gender, age, procurement site and causes of death of donors, and follow-up of recipients. Statistical analysis was performed using Microsoft Excel and SPSS 24.0. Significance level was set at a P value < 0.05. The overall pathogen positive rate was 9.8% (n = 8), including 7 (87.5%) fungi and 1 (12.5%) bacteria. They were 2 (2.44%) Fusarium, 2 (2.44%) Chromomycosis, 1 (1.22%) Candida albicans, 1 (1.22%) Aspergillus versicolor, 1 (1.22%) Acremonium species, and 1 (1.22%) Enterococcus. 5 contaminated corneas were used for penetrating keratoplasty; although four out of five (80%) had not been given antifungal drugs during more than 6 months following-up period, none of the recipients was infected with a graft. Donor age (P = 0.839), gender (P = 0.062), procurement sites (P = 0.713) and cause of death (P = 0.711) had no statistically significant influence on the contamination rate. All donor corneas have a possibility of microbiological contamination. Strict tissue preservation protocol but not antifungal drugs following keratoplasty seems necessary to prevent graft infection.

Increased sensitivity of microbiological testing of cornea organ culture medium by additional resin treatment

Objective

This validation study investigates the treatment of cornea organ culture medium (Modified Eagle Medium, Biochrom GmbH, Berlin, Germany) with RESEP, a new medical device for antibiotics removal, before microbiological testing with BACTEC ^TM blood culture bottles.

Methods and analysis

10–100 colony forming units of Staphylococcus aureus, Pseudomonas aeruginosa, Candida albicans, Bacillus subtillis, Aspergillus brasiliensis, Clostridium sporogenes, Enterobacter cloacae and Staphylococcus epidermidis were inoculated in 9mL of cornea organ culture medium. In group A, the medium was withdrawn with RESEP and treated for 20 min at room temperature, and then inoculated in BACTEC Plus Aerobic/F/Anaerobic/F blood culture bottles. In group B, the medium, spiked by the inoculation of microorganism, was injected directly. For each strain, a growth control was performed, by direct inoculation of the microorganisms in BACTEC^TMvials (positive control). All samples were incubated in the automated BACTEC^TMblood culture system at 36°C ±1°C for maximum of 14 days or until a positive reading. The elimination of antibiotics from the medium by RESEP was determined by high-performance liqiud chromatography.

Results

After 20 min of RESEP treatment, 100% (n=9) of streptomycin, 100% (n=9) of amphotericin B and 99.7% (n=9) of penicillin G were eliminated. In group A, all microorganisms were detected within 3 days of incubation with a sensitivity of 100% (n=99) and showed no significant delay compared with the positive controls. In group B, the overall sensitivity was 67.9% (n=96) with a significant delay until detection of microbial growth for all tested microorganisms except for A. brasiliensis.

Conlclusion

The use of RESEP to eliminate the antibiotics from cornea organ culture medium increases the sensitivity of the microbiological testing with BACTEC^TMPlus blood culture bottles significantly and fulfils the requirements of the European Pharmacopoeia method suitability test.

Candida parapsilosis Infection After Crescentic Lamellar Wedge Resection in Pellucid Marginal Degeneration

Infectious keratitis after corneal lamellar surgery is a rare complication. In this report, we present unexpected complications after crescentic lamellar wedge resection (CLWR) and their treatment in a patient with pellucid marginal degeneration. A 42-year-old male patient developed fungal keratitis due to Candida parapsilosis in the late postoperative period after CLWR. Infection was controlled with medical treatment. However, recurrent intraocular infections and cataract formation occurred, probably due to capsular damage and inoculation of microorganisms into the crystalline lens during antifungal drug injection. Lensectomy was performed due to cataract progression and recurrence of the infection when treatment was discontinued. Amphotericin B was administered to the anterior chamber at the end of the operation. Four months later, an intraocular lens was implanted and corneal cross-linking treatment was performed. At the last visit, visual acuity reached 9/10. This case shows that good visual acuity can be achieved with appropriate treatment of fungal keratitis and all associated complications after CLWR.

Infectious crystalline keratopathy

Infectious crystalline keratopathy was first reported by Gorovoy and colleagues in 1983 when they identified bacteria colonizing a cornea after a penetrating keratoplasty. Subsequent cases have elaborated on the organisms responsible and the management outcomes. Patients present with a white or gray branching opacity originating from an epithelial defect, commonly after a penetrating keratoplasty. Local immunosuppression contributes to the quiescent nature and the limited inflammatory response associated with infectious crystalline keratopathy. Diagnosis of the infective pathogens may be difficult, with a corneal scraping often being too superficial to obtain an adequate specimen. A biofilm is present that advantages microorganism survival, reduces antibiotic bioavailability, and inhibits diagnostic microbial detection. Treatment begins with topical antimicrobials, initially broad spectrum and then targeted to microorganism sensitivity. Adjunctive therapies to enhance the efficacy of treatment include disruption of the microorganism biofilm by laser, intrastromal antibiotics, and keratectomy. In recalcitrant cases, or where corneal scarring ensues, corneal transplantation is required.

Shifting trends in microbial keratitis following penetrating keratoplasty in Taiwan

To investigate the clinical and microbiological profiles from microbial keratitis following penetrating keratoplasty (PKP) in a tertiary referral center in Taiwan, the medical records of 648 consecutive patients (648 eyes) undergoing PKP between January 2003 and December 2007 were retrospectively reviewed. Patients who subsequently sustained microbial keratitis were enrolled and analyzed for potential risk factors, clinical manifestations, microbiological profiles, complications, graft survival, and final visual outcome. A total number of 42 corneal graft infections (6.5%) were recruited. Mean interval between corneal transplantation and graft infection was 12 ± 9.5 months. Potential risk factors included suture-related problems (31.0%), lid abnormalities (23.8%), persistent epithelial defect (23.8%), contact lens use (14.3%), dry eye (11.9%), and prior rejection episodes (4.8%). Lesions were discovered mostly at the donor-recipient junction ([DRJ] 45.2%). Positive cultures were identified in all of the morbid eyes, of which Pseudomonas aeruginosa was the most common pathogen (38.1%). Despite mandatory hospitalization and topical fortified antibiotics management, complications ensued such as graft failure (71.4%), hypopyon (21.4%), corneal perforation (14.3%), wound dehiscence (11.9%), and endophthalmitis (4.8%). The visual outcome was dismal that graft clarity was achieved in only 12 eyes (28.6%), and that final visual acuity deteriorated to less than 20/200 in 28 eyes (66.7%). In conclusion, microbial keratitis following PKP is a devastating event that severely impairs graft survival rate and postoperative visual outcome which usually occur within the first postoperative year. The incidence of post-PKP microbial keratitis has generally decreased in recent years whilst P. aeroginosa prevails as the leading cause of graft infection in our hospital. Close follow-up by ophthalmologists and elevated self-awareness of patients for at least one year are always encouraged to prevent late-onset infection.