Bacterial contamination of intraocular lens surgery

Fungi of the human eye: Culture to mycobiome

The focus of the current review is multi-fold and compares the diversity and abundance of fungi on the ocular surface by the conventional culture-based method with the more sensitive, high throughput, culture-independent NGS method. The aim is to highlight the existence of a core ocular mycobiome and explore the transition of the ocular fungal microbiota from the normal eye to the diseased eye. PubMed, Google Scholar and Medline were used to search for publications and reviews related to cultivable fungi and the mycobiome of the normal and diseased eye. The conventional cultivable approach and the NGS approach confirm that the eye has its own mycobiome and several confounding factors (age, gender, ethnicity etc.) influence the mycobiome. Further, dysbiosis in the mycobiome appears to be associated with ocular diseases and thus impacts the health of the human eye. Considering that the mycobiome of the eye is influenced by several confounding factors and also varies with respect to the disease status of the eye there is a need to extensively explore the mycobiome under different physiological conditions, different ethnicities, geographical regions etc. Such studies would unravel the diversity and abundance of the mycobiomes and contribute to our understanding of ocular health. Research focused on ocular mycobiomes may eventually help to build a targeted and individualized treatment.

Purifying the Air over the Operating Field and Reducing the Possibility of Airborne Contamination with a New Mobile Laminar Airflow Device

PURPOSE

To investigate the effectiveness of a mobile laminar airflow (LAF) device designed to reduce both airborne particles and lint fibers within the sterile field during cataract surgery.

SETTING

Cincinnati Eye Institute, Cincinnati, Ohio, USA.

DESIGN

Prospective case series.

METHODS

The number of airborne particles sized 0.5, 1.0 and 1.5 microns were measured at different locations and times during 116 routine phacoemulsification procedures with and without the use of a mobile LAF device. In a companion study, the presence of lint fibers in 99 eyes undergoing cataract surgery with a mobile LAF device was compared to 50 eyes in the control group. Lint fibers were differentiated as either falling onto the ocular surface or being carried into the sterile field by an instrument.

RESULTS

A statistically significant reduction (p<0.0005) occurred in all three particle sizes measurements when the LAF device was used: 79.0%, 81.7% and 90.8% in the 0.5, 1.0 and 5.0 micron particles, respectively. Lint fibers were identified in 18% of eyes in the control group and 16.16% of eyes in the LAF group. Although the number of lint fibers carried into the sterile field was similar in each group, the incidence of lint fibers falling onto the sterile field was reduced from 6% to 0% when the LAF was used (p=0.014).

CONCLUSION

The mobile LAF device is highly effective in reducing the number of particulate matter and lint fibers within the sterile surgical field when used during cataract surgery.

Microbes of the human eye: Microbiome, antimicrobial resistance and biofilm formation

BACKGROUND

The review focuses on the bacteria associated with the human eye using the dual approach of detecting cultivable bacteria and the total microbiome using next generation sequencing. The purpose of this review was to highlight the connection between antimicrobial resistance and biofilm formation in ocular bacteria.

METHODS

Pubmed was used as the source to catalogue culturable bacteria and ocular microbiomes associated with the normal eyes and those with ocular diseases, to ascertain the emergence of anti-microbial resistance with special reference to biofilm formation.

RESULTS

This review highlights the genetic strategies used by microorganisms to evade the lethal effects of anti-microbial agents by tracing the connections between candidate genes and biofilm formation.

CONCLUSION

The eye has its own microbiome which needs to be extensively studied under different physiological conditions; data on eye microbiomes of people from different ethnicities, geographical regions etc. are also needed to understand how these microbiomes affect ocular health.

Influence of Optic and Haptic Materials on the Adherence of Staphylococcus Epidermidis to Intraocular Lenses: A Pilot Study

To evaluate in vitro the adherence of Staphylococcus epidermidis to intraocular lenses (IOL) of different optic and haptic materials and design, we used a quantitative cultural method. Polymethylmethacrylate (PMMA), PMMA-prolene, polyHEMA, silicone and surface-modified PMMA (wet and dry) implants were tested.

Adherence differed significantly in the various groups, with the best performance by all-PMMA IOL.

The Effect of Intraoperative Antibiotics in Irrigating Solutions on Aqueous Humor Contamination and Endophthalmitis after Phacoemulsification Surgery

PURPOSE

To determine the efficacy of intraoperative antibiotic use in irrigating solutions on aqueous humor contamination during phacoemulsification surgery and to evaluate the corresponding risk of postoperative endophthalmitis.

METHODS

644 eyes of 640 patients who underwent phacoemulsification surgery with foldable intraocular lens (IOL) implantation were included in this study. Preoperative conjunctival smears were taken and eyes were allocated to receive irrigating infusion fluid containing either balanced salt solution (BSS)-only (group 1; 322 eyes) or BSS with antibiotics (vancomycin and gentamycin) during surgery (group 2; 322 eyes). Bacterial contamination rates of aqueous humor samples taken in the beginning and at the end of operation were compared. Predictive factors for the development of postoperative endophthalmitis were determined by clinical and microbiologic analyses.

RESULTS

The rates of culture-positivity were similar between group 1 and group 2 for both preoperative conjunctival smears and aqueous samples (p > 0.05). Aqueous samples taken at the end of operation were found to be contaminated in 68 (21.1%) eyes in group 1 and 22 (6.8%) eyes in group 2, and the difference was significant (p = 0.0001; OR = 3.65 (2.1-6.0)). Capsular rupture was associated with higher rate of contamination in both groups (p = 0.0001; OR = 7.7 and p = 0.0001; OR = 8.1). Two eyes in the BSS-only group developed postoperative endophthalmitis and these cases had posterior capsular rupture during the surgery and culture-positivity for staphylococcus epidermidis throughout the study.

CONCLUSIONS

Intraoperative antibiotic irrigation decreases aqueous humor contamination during phacoemulsification. Further studies are warranted to determine the interrelationship between aqueous humor contamination and endophthalmitis in eyes with posterior capsular rupture.

Molecular characterization and potential sources of aqueous humor bacterial contamination during phacoemulsification with intraocular lens implantation in dogs

Bacterial contamination of the anterior chamber during cataract surgery is one of the main responsible for endophthalmitis postoperative. Phacoemulsification is a less invasive technique for cataract treatment, although it does not exclude the possibility of contamination. In this study, bacterial contaminants of aqueous humor collected pre- and post-phacoemulsification with intraocular lens implantation (IOL) of twenty dogs were identified. As the conjunctival microbiota constitute a significant source of anterior chamber contamination, bacterial isolates from aqueous humor were genetically compared with those present in the conjunctival surface of the patients. Three dogs presented bacterial growth in both aqueous humor and conjunctival surface samples. Bacterial isolates from these samples were grouped according to their genetic profiles by repetitive-element PCR (rep-PCR) and their representatives were identified by 16S rRNA sequencing. Isolates from conjunctival surface were identified as Enterobacter spp., Staphylococcus spp. and S. aureus; and from aqueous humor samples as Enterobacter spp., Pantoea spp., Streptococcus spp. and Staphylococcus spp., respectively in decreasing order of prevalence. According to the rep-PCR analysis, 16.6% of Enterobacter spp. isolates from conjunctival surface were genetically similar to those from aqueous humor. The rest of isolates encountered in aqueous humor were genetically distinct from those of conjunctival surface. The significant genetic diversity of bacterial isolates found in the aqueous humor samples after surgery denoted the possibility of anterior chamber contamination during phacoemulsification by bacteria not only from conjunctival surface but also from different sources related to surgical environment.

Microencapsulation of rifampicin for the prevention of endophthalmitis: In vitro release studies and antibacterial assessment

Rifampicin encapsulated microparticles were designed for intraocular injection after cataract surgery to prevent postoperative endophthalmitis. Microparticles were formulated by emulsification diffusion method using poly(lactic acid-co-glycolic acid) (PLGA) as polymer in order to propose a new form of rifampicin that overcome its limitations in intraocular delivery. Depending on processing formulation, different types of microparticles were prepared, characterized and evaluated by in vitro release studies. Two types of microparticles were selected to get a burst release of rifampicin, to reach minimal inhibitory concentrations to inhibit 90% of Staphylococcus epidermidis mainly involved in postoperative endophthalmitis, combined with a sustained release to maintain rifampicin concentration over 24h. The antibacterial activity and antiadhesive property on intraocular lenses were evaluated on S. epidermidis. Microparticles, with a rapid rifampicin release profile, showed an effect towards bacteria development similar to free rifampicin over 48h. However, slow-release profile microparticles exhibited a similar antibacterial effect during the first 24h, and were able to destroy all the S epidermidis in the medium after 30h. The association of the two formulations allowed obtaining interesting antibacterial profile. Moreover, rifampicin-loaded microparticles have shown a very efficient anti-adherent effect of S. epidermidis on intraocular lenses at 24h. These results propose rifampicin microparticles as suitable for antibioprophylaxis of the postoperative endophthalmitis.

An 8-year retrospective study of cataract surgery and postoperative endophthalmitis: injectable intraocular lenses may reduce the incidence of postoperative endophthalmitis

BACKGROUND/AIMS

Postoperative endophthalmitis (POE) is a rare but potentially devastating complication of modern cataract surgery. We examine whether the use of injectable intraocular lenses (IOLs) is associated with a lower rate of POE after cataract surgery compared with forceps-inserted foldable IOLs.

METHODS

A single-centre retrospective cohort study of 25 410 cataract operations was performed over an 8-year period when standard practice in cataract surgery changed from the use of forceps-inserted foldable IOLs to injectable IOLs. Cases of POE were identified and the rates compared between the two groups.

RESULTS

Twelve cases of POE were identified in the study period. The rate of POE was significantly lower in the injectable IOL group compared with the forceps-inserted foldable IOL group (0.008% vs 0.081%, p=0.008). This difference remained significant when controlling for posterior capsular rupture and lens material.

CONCLUSIONS

This study, the largest of its kind to date, supports the use of injectable IOLs over forceps-inserted foldable IOLs as a significant measure in reducing the risk of POE.

Biofilms in infections of the eye

The ability to form biofilms in a variety of environments is a common trait of bacteria, and may represent one of the earliest defenses against predation. Biofilms are multicellular communities usually held together by a polymeric matrix, ranging from capsular material to cell lysate. In a structure that imposes diffusion limits, environmental microgradients arise to which individual bacteria adapt their physiologies, resulting in the gamut of physiological diversity. Additionally, the proximity of cells within the biofilm creates the opportunity for coordinated behaviors through cell–cell communication using diffusible signals, the most well documented being quorum sensing. Biofilms form on abiotic or biotic surfaces, and because of that are associated with a large proportion of human infections. Biofilm formation imposes a limitation on the uses and design of ocular devices, such as intraocular lenses, posterior contact lenses, scleral buckles, conjunctival plugs, lacrimal intubation devices and orbital implants. In the absence of abiotic materials, biofilms have been observed on the capsule, and in the corneal stroma. As the evidence for the involvement of microbial biofilms in many ocular infections has become compelling, developing new strategies to prevent their formation or to eradicate them at the site of infection, has become a priority.

Chronic postoperative endophthalmitis: a review of clinical characteristics, microbiology, treatment strategies, and outcomes

Chronic postoperative endophthalmitis (CPE) is a delayed infectious intraocular inflammation process that occurs more than six weeks after ocular surgery and frequently masquerades as autoimmune uveitis. These cases are at risk of delayed diagnosis and erroneous long-term treatment with corticosteroids. This paper aims to review the epidemiology, microbiology, clinical characteristics, diagnosis, management strategies, and outcome of chronic postoperative endophthalmitis. The incidence of CPE is still uncommon, and multiple pathogens have been reported with varying frequencies. Review of the literature reveals that CPE cases have a high incidence of visual impairment and recurrence rate might be decreased with aggressive surgical approach.

[Intraocular lens and bacterial adhesion: influence of the environmental factors, the characteristics of the bacteria, and the target material surface]

Adhesion of bacteria to intraocular lenses is an important step in the pathogenesis of postoperative endophthalmitis. It can be described as a two-phase process including an initial, instantaneous, and reversible phase followed by a time-dependant and irreversible molecular and cellular phase. The binding of bacteria is affected by many factors including environmental factors such as medium composition, presence of proteins and flow conditions, the bacterial cell surface characteristics, and the material's surface properties. This article reviews all these factors affecting the adhesion of bacteria to intraocular lenses. A better understanding of these mechanisms would make it possible to reduce the bacterial adhesion process and thus could help decrease the incidence of postoperative endophthalmitis.

Endophthalmitis after cataract surgery: a nationwide prospective study evaluating incidence in relation to incision type and location

PURPOSE

To establish the nationwide rate of postoperative endophthalmitis (PE) after cataract extraction (CE) and to study the relationship between PE and type of incision and other possible risk factors.

DESIGN

Prospective, multicenter, comparative, nonrandomized, observational study.

PARTICIPANTS

All cataract surgeries in Sweden performed from January 2002 through December 2004 and all endophthalmitis cases in the same period that were reported to the Swedish National Cataract Register (NCR).

METHODS

Through a standard reporting form sent to the NCR, patient and operation technique data were recorded. In addition, PE cases with a traceable number to the main register were collected. Various parameters with a possible impact on endophthalmitis development were evaluated. Univariate analyses and logistic regression were statistical methods.

MAIN OUTCOME MEASURES

The rate and etiology of PE; possible risk factors pertaining to patient history and operation technique, with a special emphasis on incision type and location; use of injector for the intraocular lens implantation; kind of prophylaxis; and presence of peroperative communication between the anterior chamber and vitreous.

RESULTS

The overall rate of PE was 0.048% (109 cases in 225 471 CEs). Incidences of PE were 0.053% with clear corneal incisions and 0.036% with sclerocorneal incisions (P = 0.14, logistic regression analysis). The corresponding results were 0.040% for superior incisions and 0.055% for temporal incisions (P = 0.14). Communication between the anterior segment and vitreous was found to be a highly significant independent risk factor for PE (P<0.001), as were patient age > or = 85 years (P<0.001) and the nonuse of intracameral cefuroxime (P<0.001).

CONCLUSIONS

The overall rate of PE after cataract surgery is low in Sweden, which may be a consequence of the widespread use of prophylactic intracameral cefuroxime. Only a trend for an increased risk of PE was detected for clear corneal and temporal wounds. The present data indicate that the use of clear corneal and/or temporal approaches will result in 1 additional PE case in approximately 5500 procedures on top of the PE rate after sclerocorneal or superior incisions, which was approximately 1 case in 2400 operations.

Adhésion bactérienne aux implants intraoculaires et prévention de l'endophtalmie

Bacterial adhesion to intraocular lenses (IOLs) during their implantation is a major etiological factor of postoperative endophthalmitis. Polypropylene was the first biomaterial that allowed this relation of cause and effect between bacterial adhesion and endophthalmitis to be proven. Adhesion to IOLs has been investigated in several in vitro studies, with contradictory results reported, due to variations in experimental conditions: the incubation times and the methods all varied. Adhesion is affected by the type of IOL, the bacterial strains, and the surrounding medium. Since this medium is very difficult to model because of its complexity, in vivo studies seemed essential. We have recently determined in vivo progression in the amount of adhering Staphylococcus epidermidis to five types of IOLs. There have been few epidemiological studies published to determine the relationship between endophthalmitis and the IOL type. However, the perfect biomaterial that could prevent postoperative endophthalmitis does not yet exist. Globally, hydrophilic materials and hydrophobic acrylic seem to be less sticky than silicone or PMMA, but this remains to be proven clinically.

Endophtalmie : étiopathogénie et antibioprophylaxie

Postoperative endophthalmitis is still one of the most fearsome complications of cataract surgery. The present review's aims are to study the etiology and pathogenesis of endophthalmitis and the criteria for antibiotic prophylaxis. Endophthalmitis prevalence is 0.07%-0.32% in cataract surgery. The clinical presentation needs to be perfectly known, even if none of the signs is pathognomonic. Bacteria predominantly cultured in postoperative endophthalmitis are gram-positive, especially Staphylococcus epidermidis. Most of the bacteria come from the patient. Bacterial adhesion to intraocular lenses (IOLs) takes place during their implantation, a prominent etiological factor. Polypropylene was the first biomaterial that proved this relation of cause and effect between bacterial adhesion and endophthalmitis. The benefit of antibiotic prophylaxis during cataract surgery has yet not been proven, since the low prevalence of endophthalmitis makes controlled studies with a large cohort difficult. The criteria and the four possible administration approaches (topical, subconjunctival, irrigation liquid, systemic) are analyzed.

In vitro influence of vancomycin on adhesion of a Staphylococcus epidermidis strain encoding intercellular adhesion locus ica to intraocular lenses

PURPOSE

To assess anti-adhesion and/or bactericidal properties of vancomycin in vitro and to determine when these effects are detectable to estimate its relevance to perioperative antibiotic prophylaxis and analyze the efficacy of a newly designed vancomycin insert prototype for endophthalmitis prevention.

SETTING

University research laboratory, Lyon, France.

METHODS

Staphylococcus epidermidis clinical strain N890074 containing the intercellular adhesion locus ica was used as the infectious agent. Vancomycin was used at 20 microg/mL. A sterile biocompatible, biodegradable vancomycin insert, releasing 230 microg of antibiotics over 100 minutes, was designed especially for this study. To obtain bacterial killing curves, experiments were first performed in a 103 colony-forming units (CFU/mL) bacterial suspension containing no intraocular lenses (IOL). Then IOLs were incubated in the suspension, and bacterial adherence was determined using bacterial counting with and without antibiotic.

RESULTS

Vancomycin (solution and insert) had an anti-adhesion effect after 1 hour and a relevant bactericidal effect after 6 hours of incubation.

CONCLUSIONS

Vancomycin used with irrigating solutions does not remain in the anterior chamber long enough to develop bactericidal effect. Even if it initially reduces bacterial adhesion, used at a drug level dropping below the bacterial minimal inhibitory concentration, it could result in a secondary increase of the adhesion of slime-producing bacteria. A sufficiently high concentration was obtained in vitro by the new sustained-release system, thereby overcoming the theoretical drawback of a short half-life within the anterior chamber. Anti-adhesion and bactericidal action of vancomycin inserts remains to be confirmed in clinical studies.

Biofilms à Staphylococcus epidermidis à la surface des implants intraoculaires

Bacterial adhesion to intraocular lenses (IOLs) takes place during their implantation. This is a prominent etiological factor of postoperative endophthalmitis. Following adhesion, secretion of an extracellular matrix (called slime for Staphylococcus epidermidis) and formation of multiple layers of microcolonies lead to the colonization of the biomaterial surface. Scanning electron microscopy photographs illustrate the different steps of biofilm formation. The different adhesins expressed by S. epidermidis involved in the adhesion process are described. The biofilm is not only an adhesive medium; it also affects virulence. Last, notions on biofilm physiology are discussed in an attempt to explain the dynamic equilibrium of this system. In 2004, the perfect biomaterial able to prevent postoperative endophthalmitis does not yet exist. Moreover, there is no effective tool, at the present time, to fight against mature biofilms. Therefore, preventing biofilm formation remains capital, which requires perfect knowledge of all stages of formation and the factors involved.

Microbial contamination of the anterior chamber during cataract phacoemulsification and intraocular lens implantation in dogs

The objective of this study was to determine the frequency of intraoperative contamination of the anterior chamber with viable microorganisms during cataract phacoemulsification and intraocular lens implantation, and to evaluate the relationship of contaminant microorganisms to patients' extraocular and nasal cavity floras. Also, the impact of various aspects of the patient history and phacoemulsification procedure on the incidence of positive postoperative anterior chamber cultures was investigated. Twenty-two eyes from 13 dogs presented for elective cataract phacoemulsification and intraocular lens implantation were studied. Preoperatively, microbiologic samples of the conjunctiva, eyelid margins, nares, and rostral nasal cavity were collected. Postoperatively, anterior chamber fluid was aspirated. Samples were submitted for aerobic/anaerobic bacteriologic culture and antimicrobial susceptibility, Mycoplasma culture, and fungal culture. Anterior chamber aspirates collected at the conclusion of surgery were culture positive for at least one organism in 22.7% of eyes. Three aerobic bacteria and three fungi were isolated from the anterior chamber aspirates. Two fungi and one bacterium isolated from the anterior chamber were typed identically, and the bacterium had a similar antibiogram to organisms recovered from the patient's conjunctiva and eyelid margin. No statistically significant difference in contamination frequency was found for the investigated patient and surgical variables. We conclude that intraoperative contamination of the anterior chamber with viable bacterial and fungal organisms is a common occurrence in canine patients undergoing cataract phacoemulsification and intraocular lens implantation, and the external ocular flora is a likely source of some of these contaminating microorganisms. This contamination is independent of the patient and surgical variables investigated.

Folding procedure for acrylic intraocular lenses

PURPOSE

To compare in vitro the effect of 2 standard methods of folding acrylic intraocular lenses (IOLs) on surface characteristics and bacterial adhesion.

SETTING

Eye Clinic and Department of Health-Microbiology Unit, University of Florence, Florence, Italy.

METHODS

To evaluate the effect of folding, 2 types of acrylic IOLs were not folded or folded with a forceps or an injector and then processed for scanning electron microscopy (SEM) examination. Bacterial adhesion was assessed using an ocular isolate of Pseudomonas aeruginosa. Nonfolded and folded IOLs were placed in test tubes containing the bacterial suspension for direct counting of viable adherent bacteria and for SEM.

RESULTS

The injector-folded IOLs did not show major alterations on the surface; 5 of the 9 forceps-folded IOLs showed marks or scratches in the profile of the optic. The mean number of viable adherent bacteria per area of IOL optic was 1082 (95% confidence interval [CI], 835-1330) in forceps-folded IOLs, 366 (95% CI, 192-359) in injector-folded IOLs, and 206 (95% CI, 123-289) in nonfolded IOLs. Scanning electron microscopy confirmed more surface irregularities on forceps-folded IOLs, with bacteria adherent preferentially on the surface scratches.

CONCLUSION

Forceps-folding provoked more surface irregularities, which probably make IOLs more susceptible to bacterial adhesion.

Microbial contamination of the anterior chamber during phacoemulsification

PURPOSE

To study the nature and frequency of anterior chamber contamination during phacoemulsification.

SETTING

Department of Ophthalmology, Jawaharlal Institute of Postgraduate Medical Education and Research, Pondicherry, India.

METHODS

Eighty eyes of 80 patients having routine phacoemulsification cataract surgery were recruited into this prospective study. Bacterial cultures from the intraoperative anterior chamber aspirates from the patients were assessed.

RESULTS

Anterior chamber fluid aspirates were positive for bacteria in 37 eyes (46.25%). Coagulase-negative Staphylococcus was the most common aerobe and Propionibacterium acnes, the most common anaerobe.

CONCLUSION

Results indicate that phacoemulsification has no proven advantage over conventional extracapsular cataract extraction in reducing intraoperative bacterial contamination.

A comparison of endophthalmitis after phacoemulsification or extracapsular cataract extraction in a socio-economically deprived environment: a retrospective analysis of 2446 patients

PURPOSE

To assess which cataract operation technique involves least risk of postoperative endophthalmitis, when performed in a population living in poor hygiene conditions.

METHODS

This retrospective clinical study evaluated 2446 cases at the Eye Clinic of the Komotini General Hospital, Greece, between January 1998 and January 2001.

RESULTS

Endophthalmitis arose in 12/1055 patients (1.13%) after extracapsular cataract extraction (ECCE) and in 8/1391 after phacoemulsification (0.57%). The mean time to onset of endophthalmitis was 23 and 73 days respectively after phacoemulsification and ECCE. This difference was statistically significant.

CONCLUSIONS

Endophthalmitis develops considerably later after ECCE than phacoemulsification. Thus it would appear that hygiene conditions have a stronger effect in patients operated with the ECCE technique. In order to reduce the risk of endophthalmitis after cataract extraction in patients living in substandard conditions, phacoemulsification is proposed as preferable to ECCE.

Bacterial contamination of the anterior chamber during phacoemulsification cataract surgery

PURPOSE

To determine the incidence of bacterial contamination of the anterior chamber after phacoemulsification cataract surgery with intraocular lens (IOL) implantation.

SETTING

Department of Ophthalmology, Royal Prince Alfred Hospital, Sydney, Australia.

METHODS

Ninety-eight consecutive eyes of 96 patients having phacoemulsification cataract surgery with IOL implantation were included in this prospective study. Two intraoperative anterior chamber aspirates were obtained from each patient, 1 taken at the start and the other at the conclusion of surgery. In addition, preoperative and postoperative conjunctival swabs were acquired. The 4 specimens were cultured using direct culturing techniques under aerobic and anaerobic conditions for 14 days. No preoperative antibiotics were used.

RESULTS

The incidence of intraoperative anterior chamber contamination was 0% (95% confidence interval, 0%-3.7%) as all intraoperative anterior chamber samples proved culture negative. Sixty-five percent of the preoperative conjunctival swabs were positive for growth, with corynebacteria, coagulase-negative staphylococci, and Propionibacterium acnes being the most frequently cultured organisms. Sixteen percent of the postoperative conjunctival swabs were positive for growth, with corynebacteria and coagulase-negative staphylococci being the most common bacteria. One patient developed culture-positive postoperative endophthalmitis; using pulsed-field gel electrophoresis for further typing, the implicated Staphylococcus epidermidis was indistinguishable from that isolated from the patient's preoperative conjunctival swab.

CONCLUSIONS

The bacterial contamination rate of the anterior chamber after phacoemulsification and IOL implantation was extremely low. Additional findings support the conjunctiva as being a primary source of bacteria causing postoperative endophthalmitis as well as the ability of povidone-iodine to reduce the conjunctival bacterial load.

Occlusive scrub suits in operating theaters during cataract surgery: effect on airborne contamination

The effect of wearing occlusive scrub suits on bacterial contamination of air was studied during cataract operations. All personnel regularly wore cotton scrub suits. During the intervention period, all wore occlusive scrub suits, which, compared with cotton scrub suits, were associated with more than a 50% reduction in the load of airborne bacteria during operations.

Effectiveness of ciprofloxacin and ofloxacin in a prophylaxis model of Staphylococcus keratitis

PURPOSE

To determine the effectiveness of prophylactic fluoroquinolone treatment against staphylococci in a rabbit keratitis model.

METHODS

Prophylactic ciprofloxacin or ofloxacin was applied as one topical drop 15 minutes before infection or as one drop at three time points (19, 17, and 15 minutes) before infection. In a second experiment, rabbits were treated with two, three, or four drops of ciprofloxacin 1 hour before infection. Approximately 250 colony-forming units (CFUs) of Staphylococcus aureus were injected intrastromally, and CFUs were determined 5 hours after infection.

RESULTS

The CFUs per cornea in all treatment groups were significantly less than the 5.6 +/- 0.11 log CFUs per cornea in the untreated group ( p < or = 0.0001). Rabbit eyes treated 15 minutes before infection with Ciloxan or Ocuflox had 0.96 +/- 0.48 log CFUs per cornea (three of six sterile corneas) or 1.26 +/- 0.31 log CFUs per cornea (one of six sterile corneas), respectively ( p = 0.5226). Eyes treated with Ciloxan 19, 17, and 15 minutes before infection had 0.0 +/- 0.0 log CFUs per cornea, and all eyes were sterile, whereas eyes treated with Ocuflox had 0.98 +/- 0.48 log CFUs per cornea and two of six eyes sterile ( p = 0.0435). Eyes treated 1 hour before infection with two, three, or four drops of Ciloxan had 2.61 +/- 0.69 log CFUs, 1.23 +/- 0.32 log CFUs, or 0.85 +/- 0.28 log CFUs per cornea, respectively, which was significantly less than untreated eyes ( p < or = 0.0001).

CONCLUSIONS

Multiple topical drops of a fluoroquinolone administered prophylactically were effective for subsequent staphylococcal ocular infection.

Corneoscleral rim cultures: lack of utility and implications for clinical decision-making and infection prevention in the care of patients undergoing corneal transplantation

PURPOSE

To assess the utility of donor corneoscleral rim cultures.

METHODS

A retrospective review of the culture results of 774 corneoscleral rims that remained after trephination of corneas for transplantation into patients at our academic medical center between January 1992 and November 1997.

RESULTS

Forty-one (5.3%) corneoscleral rim cultures yielded microorganisms, mostly coagulase-negative staphylococci. Two patients developed endophthalmitis (one with Staphylococcus aureus and one with Pseudomonas aeruginosa) within 3 months after transplantation; each had a negative corneoscleral rim culture and neither patient's infection was temporally related to the transplant procedure.

CONCLUSIONS

Preoperative donor corneoscleral rim cultures are unreliable predictors of endophthalmitis complicating corneal transplantation and, therefore, are not useful in the clinical management of patients having corneal transplants. Moreover, the discrepancy between the results of corneoscleral rim cultures and subsequent endophthalmitis renders them invalid as a quality assurance procedure. Instead, for patients with suspected endophthalmitis after corneal transplantation, we recommend that corneal surgeons select antimicrobial therapy based on current guidelines and the results of directed sampling. Furthermore, eye banks should prospectively track recipients who develop clinical endophthalmitis, immediately notify the corneal surgeon who transplanted the matched cornea of that used for the index case, and, in selected situations, attempt to identify a possible source of contamination.

Does surgical technique influence cataract surgery contamination?

PURPOSE

To compare cataract surgery contamination rates in large-incision extracapsular cataract extraction (ECCE) and phacoemulsification (PE), we studied 65 cases prospectively.

METHODS

Thirty-five cases were operated by large-incision ECCE (Group I) and 30 by PE (Group II). Conjunctival swab cultures were taken immediately before surgery and anterior chamber aspirate was taken for culture upon completion of surgery for each case.

RESULTS

Anterior chamber cultures were positive in 22.8% of the cases in group I and 23% in Group II. Frequencies of contamination in each group were no different (x2: 0.22, p>0.05). When the contaminations were evaluated in relation to operating time, prolongation of the operating time raised the contamination rate in Group I (p<0.05) but not in Group II (p>0.05). Silicone and PMMA intraocular lenses (IOL) were tested to see whether they had any additional risk of contamination. The frequencies of contaminated silicone IOL implanted cases (6/26) and contaminated PMMA IOL implanted cases (8/39) were similar (x2: 0.36, p>0. 05).

CONCLUSIONS

Although the architecture of the incision and irrigation dynamics provided an advantage to the PE technique as the operating time became longer, routine PE was not superior to classical ECCE with respect to contamination when performed in the same circumstances. Prolonging the operating time raised the contamination rate in classical ECCE.

Intraocular bacterial contamination during sutureless, small incision, single-port phacoemulsification

PURPOSE

To evaluate the incidence of anterior chamber bacterial contamination during no-stitch, 1-handed, small incision phacoemulsification.

SETTING

Little Company of Mary Hospital, Evergreen Park, Illinois, USA.

METHODS

This study comprised 53 eyes of 46 patients. Topical gentamicin sulfate was administered 1 hour preoperatively. After povidone-iodine cleansing solution and povidone-iodine paint (5% and 10%) were applied, the eyes were draped in a sterile manner. Aqueous fluid was aspirated upon entering the anterior chamber and at the end of surgery; the specimens were cultured for up to 14 days. All eyes had no-stitch, 1-handed, small incision phacoemulsification with implantation of a foldable acrylic posterior chamber intraocular lens through a 3.5 mm scleral tunnel incision.

RESULTS

Three specimens (5.7%) aspirated on entry into the anterior chamber were positive for microorganisms. Of the cultures obtained at the end of surgery, 4 (7.5%) were positive for microorganisms. All posterior lens capsules were intact. The following organisms were cultured at the end of phacoemulsification: alpha-streptococci, micrococci, saprophytic mold, alpha-viridans streptococci, coagulase-negative Staphylococcus species, and anaerobic positive cocci. No eye developed endophthalmitis.

CONCLUSIONS

The incidence of anterior chamber bacterial contamination was low. Bacterial contamination of the anterior chamber occurred at the beginning and toward the end of phacoemulsification. Staphylococcus species was the most common organism in the beginning, while Streptococcus species was the most common at the end. Saprophytic mold was present only at the end. No eye developed endophthalmitis.

Adherence of ocular isolates of staphylococcus epidermidis to ACRYSOF intraocular lenses. A scanning electron microscopy and molecular biology study

PURPOSE

To investigate the adherence of two clinically relevant ocular isolates of Staphylococcus epidermidis to ACRYSOF intraocular lenses (IOLs) (Alcon Surgical, Fort Worth, Texas) and to determine whether the strains under study carried the intercellular adhesion (ica) locus, which encodes production of S. epidermidis antigens mediating adherence to biomaterials.

DESIGN

Experimental study.

PARTICIPANTS

The authors examined the in vitro adherence of two clinically relevant ocular isolates of S. epidermidis (S. epidermidis 1 and S. epidermidis 2). Adherence was tested on six ACRYSOF IOLs.

METHODS

Three IOLs were placed in three separate test tubes containing 5 ml of S. epidermidis 1 suspension, and three other IOLs were placed in three test tubes containing 5 ml of S. epidermidis 2 suspension. At different times (3, 30, and 90 minutes), the IOLs were removed from the test tubes and rinsed in sterile phosphate buffered solution. The lenses were then fixed in glutaraldehyde, postfixed in osmium tetroxide, and serially dehydrated in ethyl alcohol. After critical point drying, they were sputter-coated with gold and then examined with a scanning electron microscope. In addition, polymerase chain reaction amplification was used to investigate whether the isolates under study carried the ica locus.

MAIN OUTCOME MEASURES

The number of adhered bacteria per area (square millimeters) of IOL optic was calculated. Statistical analysis included calculation of arithmetic means and 95% confidence intervals (t test). Polymerase chain reaction amplification products were visualized in ethidium bromide-stained agarose gel.

RESULTS

Direct counting of adherent bacteria in scanning electron microscopy photographs revealed that the total amount of adhered bacteria per area of IOL optic after 3, 30, and 90 minutes of incubation in bacterial suspension was 1306/mm(2), 3389/mm(2), and 7195/mm(2) (S. epidermidis 1) and 778/mm(2), 1056/mm(2), and 3861/mm(2) (S. epidermidis 2). Differences at 30 and 90 minutes were statistically significant (P: = 0.01 and 0.02, respectively). Polymerase chain reaction amplification revealed that S. epidermidis 1 contained the ica locus, whereas S. epidermidis 2 was ica negative.

CONCLUSIONS

Different ocular isolates of S. epidermidis may differ significantly with regard to adherence to ACRYSOF IOLs. Adherence appeared to be greater when the bacterial DNA contained the ica locus. Strains of S. epidermidis carrying the ica locus may play an important role in the pathogenesis of some forms of endophthalmitis occurring after cataract surgery.

In vitro adhesion of Staphylococcus epidermidis to intraocular lenses

PURPOSE

To compare the in vitro adherence of slime-producing and non-slime-producing Staphylococcus epidermidis to different intraocular lenses (IOLs) to study the organism's contribution to postoperative endophthalmitis.

METHODS

Strains of slime-positive (ATCC 35984) and slime-negative (ATCC 12228) S epidermidis were used. The IOLs were made of poly(methyl methacrylate) (PMMA), PMMA with polypropylene haptics, silicone, hydrogel, acrylic, heparin-surface-modified (HSM) PMMA, and fluorine-surface-modified PMMA. The lenses were incubated overnight with bacteria, then sonicated and vortexed to separate the adhered bacteria. Quantitative cultures were performed and the results statistically analyzed.

RESULTS

Slime-negative strains of S epidermidis adhered to all IOLs but at a lower level than slime-positive strains. The most adherent lenses were acrylic with the positive strain and PMMA with the negative strain. The least adherent IOLs were PMMA with the positive strain and hydrogel with the negative strain. There were no significant differences between rigid and foldable lenses. Polypropylene was significantly more adherent than PMMA to the slime-positive strain. The acrylic and the HSM PMMA IOLs were significantly more adherent to the positive strain.

CONCLUSIONS

In vitro, there were significant differences in bacterial adhesion among IOL materials. Slime-positive strains of S epidermidis were more adherent than slime-negative ones.

In vitro adherence of Staphylococcus epidermidis to polymethyl methacrylate and acrysof intraocular lenses

PURPOSE

To investigate the adherence of one clinically relevant ocular isolate of Staphylococcus epidermidis to polymethyl methacrylate (PMMA) and Acrysof (Alcon Surgical, Fort Worth, TX) intraocular lenses (IOLs).

DESIGN

Experimental study.

PARTICIPANTS

The authors examined the in vitro adherence of one clinically relevant ocular isolate of S. epidermidis. Adherence was tested on 12 PMMA IOLs and 12 Acrysof IOLs.

METHODS

Six IOLs (three of each type) were placed in different test tubes containing bacterial suspension (10(8) cfu/ml) and incubated at 37 degrees C. At different times (3 minutes, 30 minutes, and 90 minutes), each IOL type was removed from the test tube, rinsed in sterile phosphate-buffered saline, and transferred into sterile brain-heart infusion broth. The broth with the IOL was sonicated on low power for 3 minutes to remove adhered bacteria. Two serial 10-fold dilutions of the broth containing the dislodged bacteria were plated on mannitol agar plates. The plates were incubated overnight at 37 degrees C and then bacterial colonies were counted. All assays were performed in triplicate. Additional lenses (three of each type) were incubated with S. epidermidis for different times (3 minutes, 30 minutes, and 90 minutes) and then examined with scanning electron microscopy.

MAIN OUTCOME MEASURES

The number of adhered bacteria per area (mm ) of IOL optic was calculated. Statistical analysis included calculation of arithmetic means and 95% confidence intervals (t test).

RESULTS

Direct counting of viable adherent bacteria released by sonication showed that the amount of adhered bacteria per area of IOL optic after 3, 30, and 90 minutes' incubation in S. epidermidis suspension was 0.1 x 10(2)/mm2, 3.6 x 10(2)/mm2, and 11 x 10(2)/mm2 (PMMA IOLs), and 4.4 x 10(2)/mm2, 3.1 x 10(2)/mm2, and 2.3 x 10(2)/mm2 (Acrysof IOLs). Direct counting of adherent bacteria in scanning electron microscopy photographs revealed that the total amount of adhered bacteria per area of IOL optic after 3, 30, and 90 minutes' incubation in S. epidermidis suspension was 1.1 x 10(2)/mm2, 4.4 x 10(2)/mm2, and 5.5 x 10(2)/mm2 (PMMA IOLs) and 13 x 10(2)/mm2, 33.9 x 10(2)/mm2, and 72 x 10(2)/mm2 (Acrysof IOLs).

CONCLUSIONS

Results suggest that in vitro adherence of S. epidermidis to IOLs is influenced by IOL materials. After 3 minutes' incubation, Acrysof IOLs appeared to be more permissive to S. epidermidis adherence than PMMA IOLs. The difference was statistically significant (P < 0.05). However, at 90 minutes, Acrysof IOLs had a lower viable bacterial count than did the PMMA IOLs. Bacterial adherence appeared to be greater in areas with surface irregularities. Adherence of S. epidermidis to IOLs may play a role in the pathogenesis of some forms of endophthalmitis after cataract surgery.

Antibiotics in the irrigating solutions reduce Staphylococcus epidermidis adherence to intraocular lenses

PURPOSE

To investigate the effect of antibiotics in the irrigating solutions on hydrophobicity, slime production and the adherence of Staphylococcus epidermidis to intraocular lenses (IOLs).

METHODS

A standard culture of S. epidermidis was incubated with a control phosphate-buffered saline (PBS) or PBS containing vancomycin (20 micrograms/ml) or gentamicin (8 micrograms/ml) or a combination of gentamicin and vancomycin (8 and 20 micrograms/ml, respectively) for 30, 60 and 120 min at 35 degrees C. The bacteria were harvested by centrifugation, and washed with PBS before incubation with IOLs for 1 h. Adhesion of bacterial cells to IOLs was determined by counting the viable cells attached to the lenses. Slime production on IOLs was measured using safranin staining. Hydrophobicity of the control cultures and cultures treated with antibiotics was assayed on the basis of the hexadecane droplet method.

RESULTS

Bacterial exposure to antibiotics produced a time-dependent significant decrease in bacterial hydrophobicity and adherence to IOLs compared with the untreated control cells (p < 0.001). Hydrophobicity showed a significant correlation with adherence (r = 0.89, p < 0.001). Gentamicin was significantly more effective than vancomycin, and the synergistic combination of gentamicin and vancomycin was the most effective in reducing bacterial adherence to IOLs, hydrophobicity and slime production.

CONCLUSIONS

The use of antibiotics in the irrigating solutions during cataract surgery may be useful in reducing bacterial adherence to IOLs. Further studies are needed to determine the clinical implications of these findings in reducing the incidence of post-operative endophthalmitis associated with IOL implantation.

Are ophthalmic surgeons aware that starch powdered surgical gloves are a risk factor in ocular surgery?

PURPOSE

To assess the level of awareness among UK ophthalmic surgeons of the potential risks from starch powdered surgical gloves during ophthalmic surgery and to show by electron microscopy that starch granule contamination can occur during ophthalmic surgery.

SETTING

A sample (N = 46) of UK ophthalmologists from the North of England, UK.

METHODS

Type of glove usage and awareness of the possible risks from starch powdered surgical gloves were assessed by means of a questionnaire sent to ophthalmic surgeons in the North of England. The surface of a polymethylmethacrylate (PMMA) intraocular lens (IOL) handled with a starch powdered surgical glove was examined by electron microscopy for evidence of starch contamination.

RESULTS

Of the sampled ophthalmic surgeons (46), 89.1% considered it important to use starch free surgical gloves and the 84.8% already did so. Starch granule contamination was seen by electron microscopy on the surface of a PMMA IOL which had been handled with starch powdered surgical gloves.

CONCLUSIONS

Although there has been sporadic attention in the ophthalmic literature to the risks associated with starch powdered surgical gloves in ophthalmology, up to 15% of UK ophthalmic surgeons may still be using starch powdered gloves. The authors show that starch powder contamination of ophthalmic materials can actually occur and remind ophthalmologists that this has been reported in the literature as a possible cause of sterile intra and extraocular inflammation.

Phacoemulsification and modern cataract surgery

The techniques and results of cataract surgery have changed dramatically during the past three decades. In the USA, we have moved from intracapsular cataract extraction as the preferred technique to almost exclusively extracapsular techniques. Smaller incisions have become the standard, with phacoemulsification now being the method of choice for most surgeons. Along with these advances have come improved intraocular lens materials and designs, especially well suited for use with smaller incisions. Phacoemulsification as a method to remove the cataractous lens was first proposed more than 20 years ago. Advances in techniques and equipment have led to a dramatic increase in the popularity of phacoemulsification with increased safety and efficiency. Viscoelastic agents have been developed synchronously with modern phacoemulsification techniques, playing an integral role in the success of this new technology. Improved surgical techniques for removing the anterior lens capsule have decreased the incidence of both intraoperative and postoperative capsular complications. Nucleus removal, formerly performed primarily in the anterior chamber, is now performed in the posterior chamber, decreasing damage to the corneal endothelium. Improved wound construction allows many wounds to be left unsutured, and smaller wounds allow shorter recovery time and greater intraoperative control and safety. Intraocular lenses can have smaller optic sizes and still maintain accurate centration. Foldable intraocular lenses can take advantage of the smaller incision, even further shortening the time to visual recovery. Continual evolution of this technology promises to further improve patient outcomes after cataract surgery.

Prospective evaluation of external ocular microbial growth and aqueous humor contamination during cataract surgery

PURPOSE

To analyze the route of aqueous humor contamination leading to the development of postoperative endophthalmitis.

SETTING

Department of Ophthalmology, University of Helsinki, Finland.

METHODS

Forty-nine eyes of 49 patients (31 having phacoemulsification and 18 extracapsular cataract extraction [ECCE]) participated in the study. Four bacterial cultures were taken: preoperative conjunctival swab, lid margin culture, intraoperative lacrimal lake sample, and immediate postoperative anterior chamber fluid sample.

RESULTS

Preoperative lid margin cultures were positive in 59.2% of eyes, conjunctival cultures in 69.4%, and lacrimal lake cultures in 24.9%. Four aqueous humor samples (8.2%) showed bacterial growth in the anterior chamber aspirate: 3 in the phacoemulsification and 1 in the ECCE group. The bacteria isolated in this study, Staphylococcus epidermidis and Propionibacterium acnes (2 positive isolates each) were sensitive to the preoperative topical antibiotics used. No aqueous humor sample or any from other locations showed gram-negative microbe growth. The most frequently recovered microbes in all samples collected from the 3 other sources were S epidermidis and other coagulase-negative staphylococcus species, followed by P acnes and other propionibacterium species. Staphylococcus aureus, and diptheroids.

CONCLUSION

The ocular surface significantly contributed to the transmission of microbes into the eye during cataract surgery. These microbes could not be eradicated by topical preoperative antibiotics. However, no patient developed postoperative endophthalmitis. Natural defense mechanisms appear to fend off a minor inoculum with these microbes of relatively low pathogenicity.

Endophthalmitis after cataract surgery: risk factors relating to technique and events of the operation and patient history: a retrospective case-control study

OBJECTIVE

This study aimed to investigate the relationship between postoperative endophthalmitis and current changes in the cataract operative technique.

DESIGN

A retrospective case-control study.

PARTICIPANTS

The 22,091 cataract operations performed from 1990 through 1993 at St Eriks Hospital formed the basis for this investigation. In a random fashion, 220 control subjects were selected to be compared with the endophthalmitis cases.

MAIN OUTCOME MEASURES

Numerous variables pertaining to the cataract extraction procedure and to the ocular and general health of patients with cataracts were analyzed regarding the development of postoperative intraocular infection. Patient age, presence of diabetes or immunosuppression, type of cataract extraction and intraocular lens (IOL), and intraoperative or postoperative complications were the principal variables assessed.

RESULTS

Fifty-seven patients with endophthalmitis were diagnosed, resulting in an overall frequency of 0.26%. Immunosuppressive treatment (P = 0.019), wound abnormality (P = 0.03), and the use of IOLs without a heparinized surface (P = 0.0023) were the only significant risk factors found in a logistic regression model.

CONCLUSIONS

The results suggest that cataract operating practice may alter the risk for endophthalmitis in that implanting a heparinized IOL and creating a tight section both seem to provide protection against this dreaded complication. Regarding patient history, an increased susceptibility was found among subjects treated with immunosuppressants. Designing a prophylactic protocol that protects against endophthalmitis more efficiently than did the study prophylaxis of 20 mg of subconjunctival gentamicin, is important not only for this patient subgroup but also for the cataract operated population at large.

Intraocular lens implants and risk of endophthalmitis

AIM

To investigate the possible association between the use of three piece foldable silicone polypropylene (SPP) intraocular lenses (IOLs) and an increased risk of postoperative endophthalmitis.

METHODS

A retrospective analysis was conducted of all cases of postoperative endophthalmitis following phacoemulsification surgery in a single unit over a 3 year period. The incidence of postoperative endophthalmitis in eyes with SPP IOLs was compared with the incidence in eyes with single piece polymethylmethacrylate (PMMA) IOLs.

RESULTS

772 cataract extractions by phacoemulsification were performed. One (0.16%) of the 622 patients with PMMA IOLs developed endophthalmitis. Excluding one patient who had aplastic anaemia, five (3.33%) of 150 patients with SPP IOLs developed endophthalmitis. The relative risk for postoperative endophthalmitis associated with the use of the SPP IOL compared with the PMMA IOL was 20.1 (p = 0.015).

CONCLUSION

This study adds further evidence to the concept that SPP IOLs can be a significant risk factor in the development of postoperative endophthamitis.

Endophthalmitis

Endophthalmitis is an inflammatory reaction of intraocular fluids or tissues. Infectious endophthalmitis is one of the most serious complications of ophthalmic surgery. Occasionally, infectious endophthalmitis is the presenting feature of an underlying systemic infection. Successful management of infectious endophthalmitis depends on timely diagnosis and institution of appropriate therapy. Recognition of the different clinical settings in which endophthalmitis occurs and awareness of the highly variable presentation it may have facilitate timely diagnosis. Biopsy of intraocular fluid/tissue is the only method that permits reliable diagnosis and treatment. The different presenting clinical settings, a rational approach to diagnosis (i.e., when, what, and how to biopsy), and the treatment of infectious endophthalmitis are reviewed.

Measurement of electrostatic charge on intraocular lenses

PURPOSE

An electronic meter that measures electrostatic charge was designed and built. The hypothesis tested was that an intraocular lens (IOL) attains a charge during handling in the operating theatre and that washing the IOL with balanced salt solution (BSS) would result in a reduction in the surface charge. Once exposed to the air a charged IOL may attract particulate matter to its surface before implantation into the eye.

METHODS

This experiment was performed in the operating theatre under sterile conditions mimicking cataract surgery. The lens box was opened onto a trolley and the lens container opened by a scrubbed assistant. The operator (also scrubbed) removed the lens with MacPherson's forceps. The charge on the lens was then measured without delay, or after the lens had been washed with 1-2 ml of BSS.

RESULTS

The mean charge on unwashed lenses was 1.43 x 10(-10) C (n = 12) and on washed lenses was 0.59 x 10(-10) C (n = 10). The difference in the charges was significant (p = 0.03, unpaired t-test).

CONCLUSION

Washing of an IOL prior to implantation will reduce the surface charge and is therefore also likely to reduce the chance of contamination.

Electron microscopy study of explanted intraocular lenses from clinically noninfected eyes

PURPOSE

To determine whether intraocular lenses (IOLs) in clinically noninfected eyes are coated with a significant, bacteria-containing biofilm.

SETTING

The Oxford Eye Hospital, Oxford, United Kingdom.

METHODS

Twenty-six IOLs, removed for reasons other than endophthalmitis from 26 patients attending the Oxford Eye Hospital over a 3 year period, were examined by electron microscopy. Immediately following explantation, the IOL was placed in glutaraldehyde 4% in 0.1 M phosphate buffer solution and processed for scanning electron microscopy (SEM). Areas of interest were reprocessed for transmission electron microscopy (TEM).

RESULTS

There was no evidence of a bacterial biofilm on any IOL. In 5 IOLs, significant host cellular debris was seen at the tip of the haptic or at the optic-haptic junction. In 4 of them, clusters of coccoid-shaped structures were seen at the optic-haptic junction on SEM, but examination by TEM showed these structures to be melanosomes, not bacteria.

CONCLUSION

We found no evidence to suggest that a significant number of IOLs are coated with a bacterial biofilm in clinically noninfected cases. We advocate the use of TEM to distinguish between coccoid bacteria and melanosomes.

Intraocular lens complications requiring removal or exchange

Intraocular lens (IOL)-related complications are caused primarily by mechanical trauma, inflammatory or infectious complications, or optical problems. Complications may occur at the time of surgery or be the result of an ongoing postoperative process. Mechanical and inflammatory injury may produce corneal decompensation, cystoid macular edema, hyphema, uveitis, and glaucoma, causing reduced vision and in some cases chronic pain. Optical problems may be due to a wrong power of the IOL or to postoperative decentration or dislocation of the lens. Ophthalmologists should be aware of the indications for IOL removal or exchange in those patients who have ongoing IOL-induced injury or impairment. Removal or exchange of an IOL frequently involves a complex decision-making process and is often associated with immense technical challenge. Various medical and surgical treatments may be tried to correct IOL problems before the decision is made to remove or exchange the lens.

Heparin and heparin-surface-modification reduce Staphylococcus epidermidis adhesion to intraocular lenses

Bacterial adherence to intraocular lenses (IOLs) could be the cause of endophthalmitis following cataract surgery and lens implantation. The majority of cases of postoperative endophthalmitis are caused by microflora that reside on or near the eye of the patient. Staphylococcus epidermidis commonly colonizes the eyelid margin and conjunctiva and is the most common organism causing postoperative endophthalmitis. In this study, the in vitro adherence of S. epidermidis to regular poly-methyl methacrylate (PMMA) IOLs and to heparin-surface-modified (HSM) PMMA IOLs was investigated. The effects of heparin and antibiotics in solution on the adherence of bacteria to regular PMMA IOLs were evaluated. Adhesion of bacterial cells to IOLs was determined by counting the viable cells attached to the lenses. Significantly, fewer S. epidermidis attached to HSM-PMMA IOLs and to regular PMMA IOLs treated with heparin than to PMMA IOLs (p < 0.001). Furthermore, bacteria attached in significantly lower numbers to regular PMMA IOLs treated with heparin than to HSM-PMMA IOLs (p = 0.0031). Antibiotics in solution had no significant effect on bacterial adherence to PMMA IOLs. These data indicate that the use of HSM-PMMA IOLs and treatment of PMMA IOLs with heparin could diminish the incidence of postoperative endophthalmitis and intraocular inflammation associated with IOL implantation.

Influence of intraocular lens haptic material on bacterial isolates from anterior chamber aspirate

PURPOSE

To determine whether intraocular lens (IOL) type affects the bacterial count in anterior chamber aspirates obtained immediately after cataract surgery.

SETTING

L.V. Prasad Eye Institute, Hyderabad, India.

METHODS

This in vivo study evaluated two groups of eyes that had uneventful cataract extraction and implantation of one of two types of IOLs: all poly(methyl methacrylate) (PMMA) (n = 73) or polypropylene haptic (n = 83). Anterior chamber fluid aspirates (0.1 mL) were obtained with a 30 gauge cannula at the end of surgery and inoculated onto chocolate agar and in thioglycolate broth. Microbiology evaluation was performed using standard methods.

RESULTS

Seven eyes (9.5%) with all-PMMA IOLs and 21 (25.3%) with polypropylene haptic IOLs were positive for bacterial isolates (P = .0322; chi-square test). Mean colony count (+/-SD) was 11.43 +/- 3.78 and 13.16 +/- 4.78 colony-forming units/ milliliter in the PMMA and polypropylene haptic IOL groups, respectively. No eye developed endophthalmitis.

CONCLUSION

Polypropylene haptic IOLs were associated with a significant increase in bacteria in the anterior chamber.

Prophylactic antibiotics in cataract operations

The rationale for prophylactic antibiotics in cataract operations must be continually reevaluated in light of cost-effectiveness and adverse reactions. The principles learned from wound infections associated with general surgical procedures should be applied to the limited knowledge about the rare event of endophthalmitis. Herein the literature on experimental and clinical wound infections in general surgical procedures is reviewed, with analysis of microbial flora, pathophysiology of wound infections, and pharmacokinetics of antibiotics. Experimental and clinical studies on prophylactic antibiotics to prevent endophthalmitis are reviewed, including information on topically applied antibiotics, chemical antisepsis, and administration of subconjunctival, intracameral, and systemic antibiotics. In addition, the benefits, limitations, and risks of the various types of prophylactic antibiotics are discussed. Because of the limited data on prophylactic antibiotics in cataract operations, providing dogmatic statements is difficult. General recommendations are offered based on the currently available literature, and a stratified approach is suggested based on wound construction and number of anterior segment maneuvers.

Acute endophthalmitis outbreak after cataract surgery

PURPOSE

To evaluate the source of organisms causing an epidemic of postoperative endophthalmitis and to emphasize the importance of prompt intervention with an early diagnosis.

SETTING

S.B. Ankara Hospital Eye Department, Ankara, Turkey.

METHODS

Thirteen patients who had surgery on the same day and developed acute postoperative endophthalmitis were evaluated. Clinical patterns were observed and intraocular cultures and stains performed in 10 eyes. Broad-spectrum intravitreal antibiotics were injected on an empirical basis.

RESULTS

Intravitreal cultures showed Pseudomonas aeruginosa in four cases and coagulase-negative staphylococci in three cases; three cases were culture negative. P. aeruginosa were also isolated from irrigation solutions used on the same day. Two patients with P. aeruginosa had a visual acuity of 20/200 and 20/300, respectively.

CONCLUSION

The different culture results were probably related to the amount of inoculation, individual risk factors, and the subconjunctival antibiotic injection given at the end of surgery. That one patient with P. aeruginosa endophthalmitis retained a visual acuity of 20/200 shows the importance of rapid intravitreal antibiotic treatment.

Spectrum and susceptibilities of microbiologic isolates in the Endophthalmitis Vitrectomy Study

PURPOSE

To determine the microbiologic spectrum and antibiotic susceptibilities of infecting organisms in postoperative endophthalmitis and to evaluate the effects of operative factors on the microbiologic spectrum.

METHODS

Patients with bacterial endophthalmitis presenting within six weeks of cataract extraction or secondary intraocular lens implantation (IOL) were evaluated. Cultures and Gram stains were performed on intraocular specimens and susceptibility tests on the isolates.

RESULTS

Confirmed microbiologic growth was demonstrated from intraocular specimens from 291 of 420 patients (69.3%). Gram-positive bacteria were isolated from 274 patients (94.2%) with confirmed growth and gram-negative bacteria from 19 (6.5%). Two hundred twenty-six of the 323 isolates obtained (70.0%) were gram-positive, coagulase-negative micrococci, 32 (9.9%) Staphylococcus aureus, 29 (9.0%) Streptococcus species, seven (2.2%) Enterococcus species, ten (3.1%) miscellaneous gram-positive species, and 19 (5.9%) gram-negative species. All gram-positive isolates tested were susceptible to vancomycin. Seventeen gram-negative isolates (89%) were susceptible to both amikacin and ceftazidime and two (11%) were resistant to both. Anterior chamber or secondary IOL implantations were associated with higher rates of infection with gram-positives other than coagulase-negative micrococci than were posterior chamber IOL implantations (P = .022) or primary cataract extractions (P = .024).

CONCLUSIONS

Gram-positive, coagulase-negative micrococci predominated in this series. Vancomycin was active against all gram-positive isolates tested. Amikacin and ceftazidime showed equivalent activity against gram-negative isolates. Secondary or anterior chamber lens implantations were associated with a possible spectrum shift toward gram-positive organisms other than the coagulase-negative micrococci.

Bacterial anterior chamber contamination with foldable silicone lens implantation using a forceps and an injector

PURPOSE

To compare the rate of anterior chamber (AC) contamination during implantation of a foldable three-piece silicone lens using a forceps and an injector.

SETTING

Department of Ophthalmology, University of Saarland, Homburg (Saar), Germany.

METHODS

In a prospective, randomized study, we cultured AC aspirates of patients who had phacoemulsification with silicone lens implantation through a 3.5 mm temporal clear corneal incision. In Group A, the lens was implanted with a forceps and in Group B, with an injector. Immediately after lens implantation, the AC aspirate (0.05 to 0.10 ml) was collected and sent to the microbiology department. All cultures were incubated for 3 days. As a topical antibiotic, gentamicin was given preoperatively and intraoperatively.

RESULTS

One hundred patients (50 in each group) were examined. In each group the bacterial contamination of the AC was 2%.

CONCLUSION

Bacterial contamination of the AC was not significantly different after silicone lens implantation with a forceps and with an injector.