Intrastromal Corneal Ring Implants Associated Bacterial Infections

PURPOSE

This study examines the incidence of infection and resistance associated with Intracorneal Ring Segment (ICRS) implantation, a common outpatient surgical treatment for correcting refractive errors and corneal ectatic diseases. Although ICRS procedures are typically safe and reversible, there is a low but notable risk of microbial infections, which require prompt and sometimes invasive treatment.

METHODS

Three electronic databases, PubMed, Web of Science (WoS), and Scopus, were utilised to search for literature according to PRISMA guidelines to identify infections related to the implantation of ICRS in the cornea between January 2000 and December 2022.

RESULTS

Gram-positive organisms were involved in 86% of cases: 35.7% S. aureus, 25% coagulase-negative staphylococci species, 17.8% streptococci and 7.1% Nocardia species. Less commonly recorded were Gram-negative bacteria (14%), with Pseudomonas aeruginosa (circa 10%) and Klebsiella pneumonia (4%) being the most common Gram-negative bacteria. In rare cases, fungi have also been reported. ICRS-related bacterial infections can be categorised into early or late onset. Early onset infection typically manifests within the first few weeks after implantation and is often associated with contamination during surgery, unhygienic practices, or inadequate sterilisation techniques. On the other hand, late-onset infection may develop months or even years after the initial procedures and may be associated with persistent bacterial colonisation, secondary infections, or prolonged use of prophylactic antibiotics. S aureus is encountered in both early and late-onset infections, while Nocardia species and K. pneumoniae have generally been reported to occur in late-onset infections. In addition, vision recovery from S. aureus infections tends to be poor compared to other bacterial infections.

CONCLUSION

S. aureus is a predominant pathogen that often requires surgical intervention with poor outcomes. Early infections result from incision gaps and ring segment rubbing, while late infections are linked to prolonged antibiotic use. Further research is needed on novel antimicrobial ICRS to procure the vision.

Astigmatic Change as a Predictor of Intrastromal Corneal Ring Segment Late Extrusion

PURPOSE

To evaluate changes in keratoconic corneas implanted with intracorneal ring segments (ICRS) that have been explanted due to late extrusion of the segment after >2 years.

SETTING

Vissum Miranza, Alicante, Spain; OftalmoSalud, Lima, Peru; Minya University Hospital, Egypt.

METHODS

Retrospective, multicenter, series of cases of 23 keratoconic corneas that have been implanted for > 2 years and have been explanted due to natural extrusion of the segment. Clinical measures of visual, refractive, topographic, pachymetric and aberrometric data were analyzed. To perform exploratory factor analysis, the Kaiser-Meyer-Olkin (KMO) test was used to evaluate sampling adequacy. Factor analysis with VARIMAX rotation was used to determine the main factors of the inventory.

RESULTS

Mean time interval 5 years. Topographic findings were reversed nearly to the baseline level after segment explantation (p>0.05). Significant worsened in refractive cylinder was found pre-ICRS extrusion (p<0.05). KMO revealed a suitability of 0.528 in the preimplantation matrix (p<.001), 0.534 in the postimplantation matrix (p<.001), 0.549 in the preexplantation matrix (p=.009). Main factor obtained in the preimplantation moment included keratoconus grade, keratometric readings and visual acuities. After ICRS implantation, the most strength components were the refractive cylinder, CDVA and UDVA. Corneal aberrations were the main factors in the preexplantation analysis.

CONCLUSIONS

ICRS can be safely extracted, with a reversal of the corneal topographic data to the preoperative level. We showed a significant astigmatic change in patients implanted with ICRS before late extrusion of the segment, suggesting the role of this parameter as a prognostic factor of extrusion.

Streptococcus vestibularis atypical infectious keratits after intracorneal ring segment implantation

PURPOSE

To report the first case of an atypical infectious keratitis caused by Streptococcus vestibularis after ICRS implantation.

CASE REPORT

A 65-year-old man underwent intracorneal ring segments (ICRS) implantation for the treatment of a pellucid marginal corneal degeneration (PMCD) in his both eyes (OU). Three weeks after the surgery of the right eye (OD), the patient presented with pain, redness, and vision loss in his OD. BCVA was 20/100 Snellen equivalent in the OD. Slit-lamp examination revealed punctate whitish infiltrates along the ring segment with associated corneal stromal edema in the OD. Corneal scrapings were obtained for gram satins and bacterial and fungal cultures, and topical treatment with hourly ciprofloxacin was started. Two days later, corneal stromal edema worsened with involvement of the ring channel. Thus, the ring segment was removed and sent for cultures, and the ring channel was irrigated with vancomycin. Culture from ring segment came back positive for Streptococcus vestibularis, so topical targeted antiobiotherapy with vancomycin and erythromycin was applied. At 3 weeks of follow-up, BCVA was of 20/40 Snellen equivalent in the OD and a subtle corneal leucoma in the OD was observed in the slit-lamp examination.

CONCLUSION

Although infectious keratitis is a rare and serious disorder associated with ICRS implantation, its early recognition and management is essential in order to avoid sight-threatening complications. Thus, a prompt obtainment of corneal curettage samples and removal of ring segment becomes decisive to initiate a targeted antiobiotherapy.

Incidence and Reasons for Intrastromal Corneal Ring Segment Explantation

PURPOSE

To determine the main causes of intrastromal corneal ring segment (ICRS) explantation and define the incidence rate.

DESIGN

Multicenter, observational consecutive case series.

METHODS

Consecutive cases of ICRSs explanted in the last 10 years were reviewed. Clinical data included age of the patients at explantation, reasons for implantation and explantation, date of implantation and explantation, tunnel creation technique, and ICRS type. Main outcomes measures were the reasons for ICRS removal and the incidence rate.

RESULTS

During the study period, 121 ICRSs (119 patients) were explanted, with an explantation rate of 5.60%. Functional failure (74 eyes, 61.16%) represents the main cause for ICRS removal: of them, 48 (39.67%) ICRSs were removed for refractive failure and 26 (21.49%) in the setting of a keratoplasty related to poor visual performance of the implanted eye. In addition, 47 eyes (38.84%) had ICRS removal for anatomic failure: among them, 36 (29.75%) were explanted for spontaneous extrusion (overall extrusion rate: 1.58%), 7 (5.79%) for suspected infectious keratitis, 3 (2.48%) for corneal melting, and 1 (0.83%) for corneal perforation. Mild cases of keratoconus were more prone to be explanted because of a loss of the initial improved visual acuity, whereas spontaneous extrusion happened often in advanced cases of keratoconus.

CONCLUSIONS

We report the largest series of ICRS explantation as of this writing. The main cause of explantation was functional refractive failure followed by spontaneous extrusion of the ICRS, that is, correlated to an anatomic failure at the site of implantation in an advanced disease.

A Pyrrhic Victory: The PMN Response to Ocular Bacterial Infections

Some tissues of the eye are susceptible to damage due to their exposure to the outside environment and inability to regenerate. Immune privilege, although beneficial to the eye in terms of homeostasis and protection, can be harmful when breached or when an aberrant response occurs in the face of challenge. In this review, we highlight the role of the PMN (polymorphonuclear leukocyte) in different bacterial ocular infections that invade the immune privileged eye at the anterior and posterior segments: keratitis, conjunctivitis, uveitis, and endophthalmitis. Interestingly, the PMN response from the host seems to be necessary for pathogen clearance in ocular disease, but the inflammatory response can also be detrimental to vision retention. This "Pyrrhic Victory" scenario is explored in each type of ocular infection, with details on PMN recruitment and response at the site of ocular infection. In addition, we emphasize the differences in PMN responses between each ocular disease and its most common corresponding bacterial pathogen. The in vitro and animal models used to identify PMN responses, such as recruitment, phagocytosis, degranulation, and NETosis, are also outlined in each ocular infection. This detailed study of the ocular acute immune response to infection could provide novel therapeutic strategies for blinding diseases, provide more general information on ocular PMN responses, and reveal areas of bacterial ocular infection research that lack PMN response studies.

Intrastromal corneal ring segments for treating keratoconus

BACKGROUND

Keratoconus is a degenerative condition of the cornea that profoundly affects vision and vision-specific quality of life. The axial cornea thins and protrudes, resulting in irregularity and, eventually, scarring of the cornea. There are multiple options available for treating keratoconus. Intrastromal corneal ring segments are small, crescent-shaped plastic rings that are placed in the deep, peripheral corneal stroma in order to flatten the cornea. They are made of polymethylmethacrylate (PMMA). The procedure does not involve corneal tissue nor does it invade the central optical zone. Intrastromal corneal ring segments are approved for use when contact lenses or spectacles are no longer adequate.

OBJECTIVES

To evaluate the effectiveness and safety of intrastromal corneal ring segments as a treatment for keratoconus.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (which contains the Cochrane Eyes and Vision Trials Register) (2018, Issue 1); Ovid MEDLINE; Embase.com; PubMed; Latin American and Caribbean Health Sciences Literature Database (LILACS); ClinicalTrials.gov and the World Health Organization (WHO) International Clinical Trials Registry Platform (ICTRP). We did not implement any date or language restrictions in the electronic search for trials. We last searched the electronic databases on 25 January 2018.

SELECTION CRITERIA

Two review authors independently assessed records from the electronic searches to identify randomized controlled trials (RCTs). Disagreements were resolved by discussion.

DATA COLLECTION AND ANALYSIS

We planned for two authors to independently review full-text reports, using standard methodological procedures expected by Cochrane.

MAIN RESULTS

We found no RCTs comparing intrastromal corneal ring segments with spectacles or contact lenses.

AUTHORS' CONCLUSIONS

In the absence of eligible RCTs to review, no conclusions can be drawn.

Femtosecond-assisted intracorneal ring segment complications in keratoconus: from novelty to expertise

Objectives

To document the difference between complication rate in the early curve of practicing intracorneal stromal rings and after gaining experience.

Patients and methods

A retrospective study of 623 eyes of 417 patients with keratoconus who underwent Keraring implantation using femtosecond laser for channel creation.

Results

The main outcome measures were reported intraoperative and postoperative complications. The overall complication rate was 12.7% (79 eyes) over the 4 years with 34 eyes in the first year (5.5%) and six eyes in the fourth year (0.96%). Over the 4 years of our practice, intraoperative complications were 7.1% and postoperative complications were 5.6%. Yet, there was a significant difference in intraoperative complications between the first and the fourth year where it was 3.5% and 0.48%, respectively. This also applies to the postoperative complication rate, which decreased from 1.9% to 0.5% in the fourth year.

Conclusion

Complications with femtosecond-assisted intracorneal stromal ring procedure can be reduced by experience, making this procedure a safe and effective means of treating keratoconus. Yet, there are some complications that cannot be avoided such as sterile keratitis.

Updates on Managements for Keratoconus

Purpose

Keratoconus is a progressive disease of the cornea which can lead to blindness as irregular astigmatism increases. Currently, a variety of methods are available for the treatment of keratoconus, and in certain cases, it may be difficult to choose the most appropriate option. This article reviews available treatment modalities for keratoconus to provide the practitioner with practical and useful information for selecting the most suitable option for each individual patient.

Methods

To review treatment methods for different stages of keratoconus, PubMed (United States National Library of Medicine) and Scopus (Elsevier BV) databases were searched using the keywords “keratoconus”, “contact lens”, “cross-linking”, “Intacs”, “keratoplasty”, “gene therapy”, and “irregular astigmatism”, and related articles were reviewed based on disease assessment parameters and treatment methods.

Results

Various methods are available for the treatment of keratoconus: eyeglasses and contact lenses in the early stages, cross-linking for stabilizing disease progression, intrastromal corneal ring segments (ICRS) for reducing refractive errors or flattening the cornea, and penetrating keratoplasty (PK) and deep anterior lamellar keratoplasty (DALK), conductive keratoplasty, gene therapy and more recently, bowman layer transplantation (BL transplantation) in advanced stages of the disease. To achieve optimum results, it is essential to choose the best option for each individual patient.

Conclusions

A commonality of the reviewed papers was the advancement of novel diagnostic and treatment methods in ophthalmology, which can delay the need for corneal grafting. A better understanding of keratoconus treatment options can help enhance visual rehabilitation and prevent blindness in keratoconus patients.

Methicillin-Resistant Staphylococcus aureus Acute Keratitis After Intracorneal Ring Segment Implantation

Introduction

The purpose of this study was to report the first case of acute bacterial keratitis produced by methicillin-resistant Staphylococcus aureus after the implantation of two intracorneal ring segments during an uneventful procedure for treating keratoconus in a 13-year-old child.

Case Report

A patient with grade III keratoconus underwent an implantation of intracorneal ring segments with no complications during the procedure. Three days later, a whitish corneal infiltrate appeared in between the union of both corneal rings. Sample cultures were positive for methicillin-resistant S. aureus (MRSA). Corneal infiltrate did not improve despite intensive topical and systemic antibiotics. Melting appeared even after the explantation of both corneal rings. Keratoplasty à chaud had to be performed to preserve the eye integrity.

Conclusions

MRSA keratitis following intracorneal ring segment implantation is a rare but severe complication that can lead to a therapeutic penetrating keratoplasty to definitely cure the process.

Proteomics in the Study of Bacterial Keratitis

Bacterial keratitis is a serious ocular infection that can cause severe visual loss if treatment is not initiated at an early stage. It is most commonly caused by Staphylococcus aureus, Pseudomonas aeruginosa, Streptococcus pneumoniae, or Serratia species. Depending on the invading organism, bacterial keratitis can progress rapidly, leading to corneal destruction and potential blindness. Common risk factors for bacterial keratitis include contact lens wear, ocular trauma, ocular surface disease, ocular surgery, lid deformity, chronic use of topical steroids, contaminated ocular medications or solutions, and systemic immunosuppression. The pathogenesis of bacterial keratitis, which depends on the bacterium-host interaction and the virulence of the invading bacterium, is complicated and not completely understood. This review highlights some of the proteomic technologies that have been used to identify virulence factors and the host response to infections of bacterial keratitis in order to understand the disease process and develop improved methods of diagnosis and treatment. Although work in this field is not abundant, proteomic technologies have provided valuable information toward our current knowledge of bacterial keratitis. More studies using global proteomic approaches are warranted because it is an important tool to identify novel targets for intervention and prevention of corneal damage caused by these virulent microorganisms.

Early-onset methicillin-resistant Staphylococcus aureus keratitis and late-onset infectious keratitis in astigmatic keratotomy incision following femtosecond laser-assisted cataract surgery

A 79-year-old woman had uneventful femtosecond laser-assisted cataract surgery including paired laser astigmatic keratotomies (AKs) in the right eye. Three weeks postoperatively, a corneal infiltrate developed in the superotemporal AK incision. Cultures grew methicillin-resistant Staphylococcus aureus. The infection was treated with topical fortified vancomycin and tobramycin; full resolution required several months of therapy. Five months after cataract surgery, the patient presented with a second stromal infiltrate, also in the superotemporal AK incision. Despite negative cultures, the infiltrate resolved quickly on a short course of broad-spectrum fortified antibiotics. At 6 months, the corrected distance visual acuity was 20/30. This case demonstrates that infectious keratitis can occur following uneventful femtosecond laser-assisted AK performed concurrently with cataract surgery. We reviewed the literature on infectious keratitis following refractive keratotomy and femtosecond laser-assisted procedures. Several recommendations to prevent these infections are proposed.

FINANCIAL DISCLOSURE

No author has a financial or proprietary interest in any material or method mentioned.

Reshaping procedures for the surgical management of corneal ectasia

Corneal ectasia is a progressive, degenerative, and noninflammatory thinning disorder of the cornea. Recently developed corneal reshaping techniques have expanded the treatment armamentarium available to the corneal specialist by offering effective nontransplant options. This review summarizes the current evidence base for corneal collagen crosslinking, topography-guided photorefractive keratectomy, and intrastromal corneal ring segment implantation for the treatment of corneal ectasia by analyzing the data published between the years 2000 and 2014.

FINANCIAL DISCLOSURE

No author has a financial or proprietary interest in any material or method mentioned.

Treatment options for advanced keratoconus: A review

Traditionally, the mainstay of treatment for advanced keratoconus (KC) has been either penetrating or deep anterior lamellar keratoplasty (PK or DALK, respectively). The success of both operations, however, has been somewhat tempered by potential difficulties and complications, both intraoperatively and postoperatively. These include suture and wound-healing problems, progression of disease in the recipient rim, allograft reaction, and persistent irregular astigmatism. Taken together, these have been the inspiration for an ongoing search for less troublesome therapeutic alternatives. These include ultraviolet crosslinking and intracorneal ring segments, both of which were originally constrained in their indication exclusively to eyes with mild to moderate disease. More recently, Bowman layer transplantation has been introduced for reversing corneal ectasia in eyes with advanced KC, re-enabling comfortable contact lens wear and permitting PK and DALK to be postponed or avoided entirely. We offer a summary of the current and emerging treatment options for advanced KC, aiming to provide the corneal specialist useful information in selecting the optimal therapy for individual patients.

[Intralamellar bandage keratoplasty for the treatment of progressive keratoconus (draft report)]

The article discusses surgical options currently available for different stages of keratoconus. Indications and possible complications of each method are described in detail. So called intralamellar bandage keratoplasty, a new surgical procedure developed in the Research Institute of Eye Diseases and aimed at stabilizing the disease, is presented. Preliminary results suggest that the procedure is a promissing method for corneal thickness restitution and early stabilization of progressive keratoconus.

Post intrastromal corneal ring segments insertion complicated by Candida parapsilosis keratitis

This case report describes the clinical and histopathologic features, including molecular confirmation, of fungal keratitis after intrastromal corneal ring segments placement for keratoconus. A 52-year-old woman underwent insertion of Intacs(®) corneal implants for treatment of keratoconus. Extrusion of the implants was noted 5 months post insertion and replaced. Three months later, monocular infiltrates and an epithelial defect were observed. The Intacs were removed and the infiltrates were treated with ofloxacin and prednisolone acetate. Microbial cultures and stains were negative. The patient demonstrated flares and exacerbation one month later. Mycoplasma and/or fungus were suspected and treated without improvement. Therapeutic keratoplasty was performed 10 months following initial placement of the corneal ring implants. The keratectomy specimen was analyzed by light microscopy and a panfungal polymerase chain reaction assay. A histopathologic diagnosis of Candida parapsilosis keratitis was made and confirmed by polymerase chain reaction. One year postoperatively, a systemic workup of the patient was done with no signs of recurrence. This rare report of fungal keratitis following Intacs insertion is the first reported case of C. parapsilosis complicating Intacs implantation.

Infectious keratitis: secreted bacterial proteins that mediate corneal damage

Ocular bacterial infections are universally treated with antibiotics, which can eliminate the organism but cannot reverse the damage caused by bacterial products already present. The three very common causes of bacterial keratitis—Pseudomonas aeruginosa, Staphylococcus aureus, and Streptococcus pneumoniae—all produce proteins that directly or indirectly cause damage to the cornea that can result in reduced vision despite antibiotic treatment. Most, but not all, of these proteins are secreted toxins and enzymes that mediate host cell death, degradation of stromal collagen, cleavage of host cell surface molecules, or induction of a damaging inflammatory response. Studies of these bacterial pathogens have determined the proteins of interest that could be targets for future therapeutic options for decreasing corneal damage.

Aspergillus fumigatus keratitis following intracorneal ring segment implantation

Background

Fungal keratitis has been rarely reported following intracorneal ring segment (ICRS) inmplantation. This paper aims to report a case of fungal keratitis with aspergillus fumigatus following ICRS implantation for correction of keratoconus.

Methods

A retrospective chart review was done. Data including demographics, clinical history and presentation, microbiological analysis as well as clinical management were recorded.

Results

A 34 year old male presented with pain, photophobia, redness and decreased vision in his right eye ten days after ICRS implantation for correction of keratoconus. Slit-lamp examination showed chemosis, ciliary injection, corneal abcess with ill defined edges and hypopyon. Microbiological analysis and culture of the corneal scrapes were positive for aspergillus fumigatus. The patient did not respond to medical treatment and ended up with corneal transplantation.

Conclusion

Although rare, fungal keratitis is a serious vision threatening complication that can complicate intrastromal ring implantation. Prompt and aggressive treatment is essential to prevent irreversible reduction of vision.

Treatment strategies for corneal ectasia

PURPOSE OF REVIEW

To review the most recent management strategies for corneal ectasia after keratorefractive surgery.

RECENT FINDINGS

Management options for postoperative ectasia include conservative management with various types of contact lenses such as rigid gas permeable lenses, custom wave front-guided soft contact lenses, hybrid lenses and tandem soft contact lens-rigid gas permeable lenses. Minimally invasive surgical options including corneal ring segment implantation with Intacs, KeraRings or Ferrara rings have shown to have good results in the initial period after insertion. However, there appears to be some evidence that this initial effect may regress with time. Collagen cross-linking is also minimally invasive and has been documented to stop the progression of ectasia and in some cases may cause regression. Recently, techniques combining collagen cross-linking with intracorneal ring segments or with topography-guided excimer laser treatments have shown to have promising results.

SUMMARY

Early management of ectasia is essential to prevent its progression and to preserve visual potential. There are several management options that are available that may be used to reduce the need for corneal transplantation for these patients.