Stephen B. Kaye

Fluoroquinolones: place in ocular therapy.

The fluoroquinolones have become widely used antibacterial agents in the treatment of ocular infections, with topical, intravitreal and systemic routes of administration being used. In general, fluoroquinolones (such as ciprofloxacin, ofloxacin, lomefloxacin and norfloxacin) have good activity against gram-negative and gram-positive bacteria. Therapeutic concentrations are achieved in the cornea after topical administration so that the fluoroqinolones have largely replaced combination therapy for the treatment of bacterial keratitis. However, a second line agent is needed when resistance is likely, such as in disease caused by streptococcal species. Reversal of resistance to quinolones may not occur with withdrawal of the antibacterial. This stresses the importance of prudent prescribing to reduce the occurrence of resistance to quinolones. When used in therapeutic topical dosages, corneal toxicity does not occur. Similarly, retinal toxicity is not seen when fluoroquinolones are used at therapeutic dosages, systemically or topically. Corneal precipitation occurs, particularly with ciprofloxacin and to a lesser extent norfloxacin, but does not appear to interfere with healing. In the treatment of endophthalmitis there is reasonable penetration of systemic fluoroquinolones into the vitreous but sufficiently high concentrations to reach the minimum inhibitory concentration for 90% of isolates (MIC90) of all important micro-organisms may not be guaranteed. Systemic administration may be useful for prophylaxis after ocular trauma.

Human herpesviruses in the cornea.

AIMS To determine the sensitivity and specificity of culture, immunohistochemistry (IHC), the polymerase chain reaction (PCR), and in situ hybridisation (ISH) for detecting herpes simplex virus (HSV-1) in the cornea of patients undergoing penetrating keratoplasty. To compare the incidence of HSV-1 in the cornea with that of varicella zoster virus (VZV), cytomegalovirus (CMV), and Epstein-Barr virus (EBV). METHODS The corneas of 110 patients, 52 with a documented history of herpes keratitis (HSK) and 58 with non-herpetic corneal disease, were investigated using IHC, PCR, ISH, and culture. RESULTS HSV-1 DNA and antigen were detected in 82% and 74% respectively, of corneas of patients with HSK and in 22% and 15% of corneas of patients with no history of HSK. The sensitivity of PCR and IHC was 82% and 74% with a specificity of 78% and 85%, respectively. HSV-1 DNA and antigen were found more frequently and in increased amounts in corneas of patients with a short interval between their last attack of HSK and surgery. There was a good correlation between PCR and IHC in 71%. HSV-1 was isolated by culture in 2%. Latency associated transcripts were not detected using ISH. Evidence of VZV DNA or antigen was found significantly more frequently in the corneas of patients with a history of HSK (p<0.001). No evidence of EBV or CMV was found in any cornea. CONCLUSIONS PCR and IHC are both sensitive for the detection of HSV-1 in the cornea. A combination of PCR and IHC increases the specificity for the diagnosis of HSK to 97%. HSV-1 appears to be slowly removed from the cornea. VZV and HSV-1 may co-infect the cornea.

Penetrating and Deep Anterior Lamellar Keratoplasty for Keratoconus: A Comparison of Graft Outcomes in the United Kingdom

PURPOSE To compare outcomes after penetrating keratoplasty (PK) and deep anterior lamellar keratoplasty (DALK) for keratoconus in the United Kingdom. METHODS Patient outcome data were collected at the time of transplantation and at 1, 2, and 5 years after surgery. Data were analyzed by Kaplan-Meier survival curves, Cox regression, and binary logistic regression to determine the influence of surgical procedure on graft survival and visual outcome. RESULTS The risk of graft failure for DALK was almost twice that for PK (P = 0.02). Nineteen percent of the DALK failures occurred in the first 30 postoperative days compared with only 2% of PK failures. When these early failures were excluded, there was little difference between the 3-year graft survivals for DALK (92%; 95% confidence interval [CI], 85%-95%) and PK (94%; 95% CI, 92%-95%) (P = 0.8). Although the mean best corrected visual acuity (BCVA) was similar for the two procedures (P = 0.7), 33% of patients who underwent PK achieved a BCVA of 6/6 or better at 2 years compared with only 22% of those who underwent DALK (P < 0.001). Those with DALK were also likely to be more myopic (< -3 D) but there was little difference in scalar cylinder. CONCLUSIONS DALK had a higher overall failure rate than PK. The difference was largely accounted for by early failures, which appeared to be related to the surgeons experience. DALK recipients were less likely to achieve BCVA of 6/6 than were PK recipients and were more likely to have -3 D or worse myopia.

Collagen corneal shields

Collagen corneal shields were developed as a corneal bandage lens and are currently indicated for ocular surface protection following surgery and in traumatic and nontraumatic corneal conditions. Collagen shields are manufactured from porcine or bovine collagen and three different collagen shields are currently available with dissolution times of 12, 24, and 72 hours. The theoretical, experimental, and clinical evidence supports a role for collagen corneal shields as a drug delivery device and in the promotion of epithelial and stromal healing. Presoaking the collagen shield in a pharmacological agent with adjunctive topical treatment represents the most efficacious method of utilizing collagen shields for drug delivery. In microbial keratitis collagen shields can enhance drug delivery, promote epithelial and stromal healing, neutralize collagenases, and reduce corneal inflammation. This review will examine the evidence that supports the role of collagen shields in drug delivery and corneal wound healing. Despite a large volume of experimental (animal) work, studies on human subjects, particularly randomized controlled trials, are lacking. The authors are advocating the reassessment of the application and benefits of corneal collagen shields to clinical practice.

Minimum Inhibitory Concentrations of Standard and Novel Antimicrobials for Isolates from Bacterial Keratitis

PURPOSE To determine the minimum inhibitory concentrations (MICs) of 12 antimicrobials in current ophthalmic use and 4 potentially new alternatives against isolates from bacterial keratitis. METHODS Bacteria were collected from cases of bacterial keratitis in six centers in the United Kingdom between 2003 and 2006. MICs were measured by using susceptibility strips containing a concentration gradient of the antimicrobials penicillin, cefuroxime, ceftazidime, chloramphenicol, gentamicin, amikacin, vancomycin, teicoplanin, ciprofloxacin, ofloxacin, levofloxacin, moxifloxacin, meropenem, linezolid, tigecycline, and daptomycin. RESULTS Isolates (n = 772) were collected including coagulase negative Staphylococcus (CNS) (30%), Pseudomonas aeruginosa (23%), Staphylococcus aureus (14%), Enterobacteriaceae (14%), and streptococci (13%). Meropenem had low MICs for most isolates. All isolates except P. aeruginosa were susceptible to tigecycline. Linezolid was active against the majority of Gram-positive pathogens. Ten percent of S. aureus and 20% of CNS isolates were methicillin resistant. When systemic breakpoints were used, 84% of S. aureus isolates were susceptible to ciprofloxacin and 98% to moxifloxacin. Of the P. aeruginosa isolates, 99% were susceptible to ceftazidime, 96% to gentamicin, 99% to ciprofloxacin and 100% to moxifloxacin. More than 97% of Enterobacteriaceae isolates were susceptible to ceftazidime, gentamicin, ciprofloxacin, and moxifloxacin. CONCLUSIONS Based on systemic breakpoint data, resistance to commonly used antimicrobials was apparent. Meropenem is a potentially effective agent for ophthalmic use, with low MICs throughout all the bacterial subgroups. Tigecycline and linezolid showed good activity against particular groups and may be useful for treating bacterial keratitis resistant to current antimicrobials. Of the fluoroquinolones, moxifloxacin showed the lowest MICs and resistance for both Gram-positive and -negative bacteria.

Genetic characterization indicates that a specific subpopulation of Pseudomonas aeruginosa is associated with keratitis infections.

ABSTRACT Pseudomonas aeruginosa is a common opportunistic bacterial pathogen that causes a variety of infections in humans. Populations of P. aeruginosa are dominated by common clones that can be isolated from diverse clinical and environmental sources. To determine whether specific clones are associated with corneal infection, we used a portable genotyping microarray system to analyze a set of 63 P. aeruginosa isolates from patients with corneal ulcers (keratitis). We then used population analysis to compare the keratitis isolates to a wider collection of P. aeruginosa from various nonocular sources. We identified various markers in a subpopulation of P. aeruginosa associated with keratitis that were in strong disequilibrium with the wider P. aeruginosa population, including oriC, exoU, katN, unmodified flagellin, and the carriage of common genomic islands. The genome sequencing of a keratitis isolate (39016; representing the dominant serotype O11), which was associated with a prolonged clinical healing time, revealed several genomic islands and prophages within the accessory genome. The PCR amplification screening of all 63 keratitis isolates, however, provided little evidence for the shared carriage of specific prophages or genomic islands between serotypes. P. aeruginosa twitching motility, due to type IV pili, is implicated in corneal virulence. We demonstrated that 46% of the O11 keratitis isolates, including 39016, carry a distinctive pilA, encoding the pilin of type IV pili. Thus, the keratitis isolates were associated with specific characteristics, indicating that a subpopulation of P. aeruginosa is adapted to cause corneal infection.

Bacterial susceptibility to topical antimicrobials and clinical outcome in bacterial keratitis.

PURPOSE To investigate the relationship between the susceptibility of bacteria to topical antimicrobials and clinical outcome in microbial keratitis. METHODS Clinical outcome data were collected from patients with microbial keratitis from whom a bacterium had been isolated during the period 2003 to 2006. The minimum inhibitory concentration (MIC) was determined for the isolates against 10 antimicrobials. The determinants of the primary clinical outcome, the ratio of healing time (closure of epithelial defect) to ulcer size (HT/UA), was analyzed in a general linear model. RESULTS Complete clinical outcome and MIC data were available for 421 patients. Sixteen (4%) patients required enucleation and 23 (5%) surgical treatment; in 382 (91%) the ulcer healed with intensive topical antimicrobial therapy. There were significant correlations between HT/UA and organism type (P = 0.001), nearest distance of the ulcer to the limbus (0.02), and MIC of the first antimicrobial used or lowest MIC of combined therapy (P = 0.006). In a model including patients who received monotherapy with a fluoroquinolone who had no subsequent change in their treatment and whose ulcers healed without surgical intervention, there were significant linear associations between clinical outcome and MIC for Pseudomonas spp. (P = 0.047), Staphylococcus aureus (P = 0.04), and Enterobacteriaceae (P = 0.045), but not for Streptococcus spp. (P = 0.85) and coagulase-negative staphylococci (CNS) (P = 0.88). CONCLUSION With fluoroquinolone monotherapy, there was significant association between the MIC of the antimicrobial prescribed and the clinical outcome with all bacteria except CNS and Streptococcus spp. The approach used in this study, if used prospectively, could allow topical breakpoint susceptibility concentrations to be determined for individual antimicrobial and bacterial combinations.

A randomised, crossover, multicentre study to compare the performance of 0.1% (w/v) sodium hyaluronate with 1.4% (w/v) polyvinyl alcohol in the alleviation of symptoms associated with dry eye syndrome.

Aims To assess the safety and performance of a 0.1% (w/v) solution of sodium hyaluronate (HA, Fermavisc®, in the alleviation of symptoms of severe dry eye in comparison with a 1.4% (w/v) solution of polyvinyl alcohol.Methods A randomised, crossover, multicentre study carried out at eight centres in the UK. Eligible patients giving written informed consent were randomised to the order in which they would receive the two study products. Each treatment period lasted for 4 weeks, then the patient crossed over to the other study product. Symptoms of burning and grittiness were assessed by visual analogue scale (VAS) at each study visit and other objective clinical assessments of ocular structure and function were carried out at baseline and the end of each treatment period.Results Thirty-nine patients were entered into the study and 32 completed both treatment periods and were included in the statistical analyses. A significant improvement in the patients’ VAS assessment of burning was seen after treatment with HA (P = 0.03, 95% Confidence Interval: −23.5 to −1.1). This treatment also resulted in a significantly lower rose bengal staining score (P = 0.04, 95% Confidence Interval: −1.62 to −0.05 for the right eye).Conclusion The results show a significant clinical benefit in terms of relief of the symptom of burning when HA is applied topically to the eye three or four times per day or as required. HA also appears to have a protective effect on the corneal epithelium, as shown by a reduction in the level of staining of corneal epithelial cells by rose bengal. This study confirms that Fermavisc® is a safe and effective product for use in the alleviation of symptoms of severe dry eye syndrome.

Analyzing refractive data

Purpose: To provide a general approach to the analysis of refractive data that overcomes the shortcomings of traditional treatments and can be easily adapted to most spreadsheets. Setting: Corneal Service, Royal Liverpool Hospital, Liverpool United Kingdom, and Optometric Science Group, Rand Afrikaans University, Auckland Park, South Africa. Method: The basis of the analyses is the dioptric power matrix. Using a hypothetical sample of data on pre‐event and post‐event refractions, the calculation of the mean pre‐event and post‐event refractions and the effect of an event on the refractive outcome, for example the refractive surgical effect, are illustrated. The most important statistics, the mean and the variance–covariance of refractions, and the formal testing of hypotheses on the mean are provided. Results: The method of analysis demonstrated how an event such as cataract surgery, occlusion treatment of amblyopia, or anisometropia can be evaluated in terms of refractive outcome. Hypothesis testing showed how the significance of this effect may be demonstrated. Conclusions: This standardized method of analyzing and reporting refractive data enables a quantitative analysis and statistical hypothesis testing of the complete refractive data. This approach has generalized applicability in a range of commonly encountered contexts such as the refractive change after cataract and refractive surgery, corneal transplantation, and treatment for amblyopia or the significance of anisometropia. The method is relatively straightforward and can be adapted to most conventional spreadsheets.

Limbal stem cell deficiency and ocular phenotype in ectrodactyly-ectodermal dysplasia-clefting syndrome caused by p63 mutations

OBJECTIVE To describe the ocular phenotype in patients with ectrodactyly-ectodermal dysplasia-clefting (EEC) syndrome (MIM#604292) and to determine the pathogenic basis of visual morbidity. DESIGN Retrospective case series. PARTICIPANTS Nineteen families (23 patients) affected by EEC syndrome from the United Kingdom, Ireland, and Italy. METHODS General medical examination to fulfill the diagnostic criteria for EEC syndrome and determine the phenotypic severity. Mutational analysis of p63 was performed by polymerase chain reaction-based bidirectional Sanger sequencing. All patients with EEC syndrome underwent a complete ophthalmic examination and ocular surface assessment. Limbal stem cell deficiency (LSCD) was diagnosed clinically on the basis of corneal conjunctivalization and anatomy of the limbal palisades of Vogt. Impression cytology using immunofluorescent antibodies was performed in 1 individual. Histologic and immunohistochemical analyses were performed on a corneal button and corneal pannus from 2 EEC patients. MAIN OUTCOME MEASURES The EEC syndrome phenotypic severity (EEC score), best-corrected Snellen visual acuity (decimal fraction), slit-lamp biomicroscopy, tear function index, tear breakup time, LSCD, p63 DNA sequence variants, impression cytology, and corneal histopathology. RESULTS Eleven heterozygous missense mutations in the DNA binding domain of p63 were identified in all patients with EEC syndrome. All patients had ocular involvement and the commonest was an anomaly of the meibomian glands and lacrimal drainage system defects. The major cause of visual morbidity was progressive LSCD, which was detected in 61% (14/23). Limbal stem cell deficiency was related to advancing age and caused a progressive keratopathy, resulting in a dense vascularized corneal pannus, and eventually leading to visual impairment. Histologic analysis and impression cytology confirmed LSCD. CONCLUSIONS Heterozygous p63 mutations cause the EEC syndrome and result in visual impairment owing to progressive LSCD. There was no relationship of limbal stem cell failure with the severity of EEC syndrome, as classified by the EEC score, or the underlying molecular defect in p63. FINANCIAL DISCLOSURE(S) The authors have no proprietary or commercial interest in any of the materials discussed in this article.