Incidence of keratitis of varying severity among contact lens wearers

Contact-lens-related microbial keratitis: case report and review

Bacterial keratitis is a serious, potentially blinding, complication most often involving overnight contact lens wear. This case report reviews the management of a patient with bacterial keratitis and discusses the etiology, differential diagnosis, classification and risk factors associated with the condition.

Clinical outcomes and prognostic factors associated with acanthamoeba keratitis

PURPOSE

To describe the clinical characteristics, time of presentation, risk factors, treatment, outcomes, and prognostic factors on a recent series of Acanthamoeba keratitis (AK) treated at our institution.

METHODS

Retrospective case series of 59 patients diagnosed with AK from January 1, 2004 to December 31, 2008. Of these 59 patients, 51 had complete follow-up data and were analyzed using univariate and multivariate logistic regression analyses performed with "failure" defined as requiring a penetrating keratoplasty (PKP) and/or having (1) best-corrected visual acuity (BCVA) < 20/100 or (2) BCVA < 20/25 at the last follow-up. A single multivariate model incorporating age, sex, steroid use before diagnosis, time to diagnosis, initial visual acuity (VA), stromal involvement, and diagnostic method was performed.

RESULTS

Symptom onset was greatest in the summer and lowest in the winter. With failure defined as requiring PKP and/or final BCVA < 20/100, univariate analysis suggests that age > 50 years, female sex, initial VA < 20/50, stromal involvement, and patients with a confirmed tissue diagnosis had a significant risk for failure; however, none of these variables were significant using multivariate analysis. Univariate analysis, with failure defined as requiring PKP and/or final BCVA < 20/25, showed stromal involvement and initial VA < 20/50 were significant for failure-only initial VA < 20/50 was significant using multivariate analysis.

CONCLUSIONS

Symptom onset for AK is greatest in the summer. Patients with confirmed tissue diagnosis and female patients may have a higher risk for failure, but a larger prospective population-based study is required to confirm this. Failure is likely associated with patients who present with stromal involvement and patients presenting with an initial BCVA worse than 20/50.

Microbial keratitis at a referral center in Brazil

To describe the epidemiological and laboratory characteristics of microbial keratitis at a referral center in Brazil. Charts of all patients referred to the Ocular Microbiology Laboratory at Federal University of São Paulo (UNIFESP) from July 1975 to September 2007 were retrospectively reviewed. The following data were recorded: age, gender, involved eye, use of ocular medication, previous trauma or surgery, contact lens wear and the results of laboratory cultures. The study included 6,804 corneal cultures. The mean age was 42.1 ± 21.4 years. The male-to-female ratio was 1.5:1. Positive cultures were obtained in 3,309 (48.6%) cases. Of these, bacteria were isolated in 2,699 (39.7%), fungi in 364 (5.3%) and Acanthamoeba in 246 (3.6%) samples. Positive bacterial cultures were 2.7-fold more frequent in patients with previous use of steroids (P < 0.01), and a 30% reduction in positive bacterial cultures was observed in patients with previous use of antibiotics (P < 0.01). A total of 1,524 patients (22.4%) had a past history of ocular surgery. Contact lens wearers showed a 1.7 times greater chance of having an Acanthamoeba-positive culture (P < 0.01). Previous ocular trauma was present in 1,118 (16.4%) cases and injury caused by plants showed a 3.8 times greater chance of a positive fungal culture (P < 0.01). Bacterial organisms were identified as the most frequent agent followed by fungi and Acanthamoeba. Prescription of steroids and antibiotics prior to corneal scrapings may modify the laboratory test results. Previous corneal surgery, contact lens wear and ocular trauma have been shown to be risk factors for bacterial, Acanthamoeba and fungal keratitis, respectively.

Lens material and formulation of multipurpose solutions affects contact lens disinfection

PURPOSE

To assess the disinfection efficacy of multipurpose solutions (MPS) against different bacterial species adhered either to silicon hydrogel or to conventional hydrogel contact lenses (CLs). The influences of the MPS formulation and the chemical composition of the lens material were investigated.

METHODS

This investigation followed the standard 14729, which establishes the guidelines for assessing CL disinfecting solutions. Two commercially available (Opti-Free(®) Express(®) and Renu(®) Multiplus) solutions and one recalled solution (Complete(®) MoisturePlus™) were used in this study. After disinfection, the number of survivors was estimated by the colony forming units' method.

RESULTS

The lens material appears to influence disinfection. The conventional hydrogel polymacon exhibited the highest disinfection scores, a fact that should be related with the lack of electrostatic attraction towards the biocides and its hydrophilicity. The MPS formulation appears to have influence in disinfection efficacy as well. For most adhered bacteria, Opti-Free(®) was capable of reducing cell concentration in 4-log.

CONCLUSION

Disinfection results from multivariate factors and this study confirmed that the lens material and the MPS play a very important role in the disinfection efficacy of CL.

Pathogenesis of contact lens-associated microbial keratitis

Sight-threatening microbial keratitis associated with contact lens wear remains a serious concern for patients, eye-care practitioners, and the contact lens industry. Several decades of research and some major advances in lens and solution technology have not resulted in a decline in disease incidence. Here, we offer a perspective on the complex pathogenesis of microbial keratitis, the factors that have prevented a better understanding of this disease, and new approaches being used to tackle this important clinical problem.

Global trends in prescribing contact lenses for extended wear

Extended wear has long been the 'holy grail' of contact lenses by virtue of the increased convenience and freedom of lifestyle which they accord; however, this modality enjoyed only limited market success during the last quarter of the 20th century. The introduction of silicone hydrogel materials into the market at the beginning of this century heralded the promise of successful extended wear due to the superior oxygen performance of this lens type. To assess patterns of contact lens fitting, including extended wear, over the past decade, up to 1000 survey forms were sent to contact lens fitters in Australia, Canada, Japan, the Netherlands, Norway, the UK and the USA each year between 2000 and 2009. Practitioners were asked to record data relating to the first 10 contact lens fits or refits performed after receiving the survey form. Analysis of returned forms revealed that, averaged over this period, 9% of all soft lenses prescribed were for extended wear, with national figures ranging from 2% in Japan to 17% in Norway. The trend over the past decade has been for an increase from about 5% of all soft lens fits in 2000 to a peak of between 9 and 12% between 2002 and 2007, followed by a decline to around 7% in 2009. A person receiving extended wear lenses is likely to be an older female who is being refitted with silicone hydrogel lenses for full-time wear. Although extended wear has yet again failed to fulfil the promise of being the dominant contact lens wearing modality, it is still a viable option for many people.

Risk factors for corneal infiltrative events during continuous wear of silicone hydrogel contact lenses

PURPOSE

This study determined which microbiologic, clinical, demographic, and behavioral factors are associated with corneal infiltrative events (CIEs) during continuous wear of silicone hydrogel (SH) contact lenses.

METHODS

Subjects (n = 205) were fitted with lotrafilcon A lenses for continuous wear and observed for 1 year. The main exposures of interest were corneal staining and bacterial lens contamination. Kaplan-Meier (KM) plots were used to estimate the cumulative unadjusted probability of remaining CIE free, and Cox proportional hazards regression was used to model the hazard of having a CIE, as a function of key predictor variables.

RESULTS

The KM-unadjusted cumulative probability of remaining CIE free was 73.3%. Approximately 53% of subjects had repeated episodes of corneal staining (mild or greater), and 11.3% had repeated episodes of moderate or greater corneal staining. Corneal staining was not associated with the development of a CIE. The frequency of substantial bacterial bioburden on worn lenses at the time of a CIE was 64.7%, compared with only 12.2% during uncomplicated wear. The presence of substantial lens bacterial bioburden was associated with the development of a CIE (adjusted hazards ratio [HR], 8.66; 95% confidence interval [CI], 2.88-26.01). Smoking was also associated with a CIE (adjusted HR, 4.13; 95% CI, 1.27-13.45).

CONCLUSIONS

Corneal staining is common during continuous wear of SH lenses, but it is not associated with the development of a CIE. Smoking and substantial lens bacterial bioburden pose prominent risks of a CIE. In this study, more than 70% of the total risk of CIE in those with substantial lens bioburden is attributable to this exposure. (ClinicalTrials.gov number, NCT00727402).

The impact of inoculation parameters on the pathogenesis of contact lens-related infectious keratitis

PURPOSE

Contact lens wear predisposes to Pseudomonas aeruginosa keratitis, but the mechanisms involved remain unclear. An in vivo model was used to study lens inoculation conditions enabling disease.

METHODS

Custom-made hydrogel contact lenses were fitted to rats after incubation in P. aeruginosa approximately 10(11) cfu/mL (3 hours) or approximately 10(3) cfu/mL (24 hours). Another group was inadvertently inoculated with a suction pen previously used with high inocula, but rinsed in ethanol and stored dry (6 months). Some corneas were tissue paper-blotted to cause fluorescein staining before lens fitting. Contralateral eyes were untreated. Twenty-four hours after disease detection, lenses were transferred to naive rats or examined by confocal microscopy before homogenization to quantify viable bacteria. After lens removal, corneas were washed to collect nonadherent bacteria and were analyzed by immunohistochemistry.

RESULTS

All eyes challenged with unworn contaminated lenses developed keratitis after approximately 7 to 10 days. Disease delay and severity were unaffected by inoculum parameters or tissue blotting but occurred sooner with lenses transferred from infected eyes ( approximately 2 days). Worn lenses and corneal washes contained infecting bacteria. Posterior, not anterior, lens surfaces harbored P. aeruginosa biofilms that penetrated the lens matrix. Diseased corneas showed an infiltration of phagocytes and T-lymphocytes.

CONCLUSIONS

P. aeruginosa induces keratitis in this lens-wearing model after a single inoculation. Delayed disease onset was interesting considering the greater keratitis risk during extended wear. Infection did not require the disruption of corneal barrier function before lens wear and occurred without exposure to lens care solutions. The data suggest that keratitis involves biofilm formation or other bacterial adaptations in vivo.

Grading contact lens-related microbial keratitis: relevance to disease burden

PURPOSE

To describe a clinical grading system for epidemiological investigation of presumed contact lens related microbial keratitis (MK) and investigate the relationship to associated costs and disease duration.

METHODS

Eligible cases identified via surveillance required positive culture or presence of at least one clinical criterion: part of the lesion within the central 4 mm of the cornea, any anterior chamber reaction, or significant pain. Two reviewers graded cases as severe MK with vision loss (two lines), severe MK without vision loss (positive culture or central location, peripheral but >2 mm or with a hypopyon) or mild MK (remainder). The medical care, pathology, and medications comprised direct costs and loss of income, assistance of carers, and purchase of spectacles comprised indirect costs; these were calculated in Australian dollars (AU$). Duration of disease was estimated from duration of symptoms (days). Outcome measures were compared between categories using a one way analysis of variance (ANOVA).

RESULTS

There were 47 of 278 (16.3%) severe with vision loss, 137 of 278 (49.3%) severe without vision loss, and 94 of 278 (33.8%) mild MK. The disease duration was 18 (6 to 95) [median (inter-quartile range)] for severe cases with vision loss, 7 (4 to 14) for severe cases without vision loss, and 4 (3 to 7) days for mild MK (ANOVA, p < 0.001). Associated costs were AU$5515 (2784 to 9437) for severe cases with vision loss, AU$1596 (774 to 4888) for severe cases without vision loss, and AU$795 (527 to 1234) for the mild MK (ANOVA, p < 0.001). Costs and symptom duration were greatest for severe disease with vision loss, less for the severe disease without vision loss, and lowest for the mild disease (p < 0.003).

CONCLUSIONS

The comparison of disease burden lends support to this clinical grading system and the concept that the severity of MK can be stratified to identify those that might be of non-infectious etiology or have a microbial cause of low virulence with minimal morbidity.

Corneal thickness change induced by dozing while wearing hydrogel and silicone hydrogel lenses

PURPOSE

The physiologic effects on the cornea of dozing while wearing contact lenses were assessed by using central corneal swelling as an index in relation with lens oxygen transmissibility (Dk/t).

METHODS

Two hydrogel lens materials (nelfilcon A and etafilcon A) with a power of -0.50 diopters (D) and three silicone hydrogel lens materials (galyfilcon A, senofilcon A, and lotrafilcon A) with a power of -0.50 D were studied on 16 eyes of eight subjects with no previous experience of contact lens wear and no ocular disease. The subjects wore the lenses for seven continuous hours with their eyelids closed for 1 hour after the first 3 hours of lens wear to simulate a dozing condition. Corneal thickness was measured with a specular microscope with a built-in pachometer (Topcon SP-2000P). The same measurement was performed for the non-lens-wearing eyes as the control.

RESULTS

Swelling rates immediately after dozing were 4.8%+/-1.4% for nelfilcon A, 5.2%+/-1.7% for etafilcon A, 2.8%+/-1.2% for galyfilcon A, 1.9%+/-0.8% for senofilcon A, and 1.5%+/-1.6% for lotrafilcon A. The swelling rates for the two hydrogel lenses were significantly higher (P<0.001) than that for the control (1.8%+/-1.5%), and the differences remained significant after 3 hours. Conversely, none of the three silicone hydrogel lenses showed a significant difference (P>0.05) compared to the control at any measurement.

CONCLUSIONS

The results indicate that dozing with silicone hydrogel lens wear causes clearly fewer intense physiologic effects in oxygen performance than dozing with hydrogel lens wear.

Microbiologic study of soft contact lenses after laser subepithelial keratectomy for myopia

PURPOSE

To evaluate the extent and agents of bacterial contamination of bandage disposable soft contact lenses after laser subepithelial keratectomy (LASEK) and to correlate the findings with clinical data.

METHODS

Disposable soft contact lenses were collected from 52 eyes of 26 consecutive patients treated with LASEK for myopia. The patients were treated with a fixed combination of tobramycin and diclofenac until epithelial closure. The lenses were removed on the fourth or fifth postoperative day with sterile forceps and immediately placed in sterile tubes containing culture media brain-heart infusion broth. The lenses were evaluated for microbial colonization.

RESULTS

Of the 52 contact lenses analyzed, six (11.5%) had positive cultures. However, no clinical finding of infection was noted. Isolated microorganisms were coagulase-negative staphylococci (two lenses), Stenotrophomonas maltophilia (two lenses), Acinetobacter species (one lens), and Aeromonas hydrophila (one lens). Except for one case, the microorganisms were sensitive to the administered antibiotic.

CONCLUSIONS

The risk of infectious keratitis after LASEK seems to be low. Except for staphylococci, the isolated microorganisms have not been previously reported to colonize the ocular surface or cause keratitis after refractive surgery. These findings may suggest a changing trend of potentially infectious agents after surface ablation.

Are inflammatory events a marker for an increased risk of microbial keratitis?

PURPOSE

To consider whether inflammatory events, such as contact lens-induced peripheral ulcers, contact lens-induced acute red eye, and infiltrative keratitis are a marker for an increased risk for the occurrence of microbial keratitis.

METHODS

A review of relevant studies was undertaken with the view to answering two questions: 1) Do inflammatory events associated with contact lens wear progress to infection or microbial keratitis; and 2) Do episodes of inflammatory events predispose a patient to having an event of microbial keratitis?

RESULTS

The large body of laboratory work, along with the epidemiologic data on incidence rates and clinical data with regard to differences between the nature of inflammatory events and infection, supports the supposition that inflammatory events are not a marker for increased risk of microbial keratitis.

CONCLUSIONS

Inflammatory events are not a marker for increased risk of microbial keratitis, nor will they progress to infection because they are separate disease entities.

Prescription and management of contact lenses in patients with monocular visual impairment

PURPOSE

Contact lens correction for refractive error in patients with monocular visual impairment may be desirable. However, the potential for damage to the sound eye must always be considered in such patients. This report outlines the prescription and management of contact lens wear in a monocular patient. The case report is followed by a discussion of the risks of vision loss associated with contact lens wear.

CASE REPORT

The author conducted a clinical interview, refraction, ocular examination, and contact lens evaluation of a 38-year-old female patient who had undergone a lensectomy in her right eye and the enucleation of her left eye. The patient presented wearing a conventional aphakic hydrogel contact lens in her right eye. She routinely wore her contact lens for up to 16 hours daily and occasionally slept while wearing it. Best-corrected spectacle acuity was 20/40-2 with +13.75 diopter sphere in her right eye. Clinical examination showed 3 to 4 mm of well-perfused neovascularization with associated pannus in the superior quadrant of her cornea and 1 to 2 mm of peripheral neovascularization in the remainder of the cornea. She was refit with a 2-week replacement hydrogel contact lens that partially corrected her refractive error, and she was encouraged to wear polycarbonate spectacles full time for the remainder of her refractive correction and for protection of the right eye.

CONCLUSIONS

Monocularly impaired patients who choose to wear contact lenses for the correction of refractive error should be aware of the risk of potentially sight-threatening contact lens complications. The importance of meticulous hygiene and appropriate contact lens wearing schedules should be emphasized with monocular patients. They should also be encouraged to wear the appropriate spectacle correction to reduce the risk of injury to their sound eyes.

Chronic morbidity of corneal infiltrative events associated with contact lens wear

PURPOSE

To determine the chronic morbidity of corneal infiltrative events (CIEs) associated with contact lens wear.

METHODS

The central corneas of both eyes of 13 subjects who had suffered a CIE 27 +/- 4 months previously were examined by using slit-lamp biomicroscopy, confocal microscopy, and ultrasound pachometry. Snellen visual acuity was recorded in both eyes. A questionnaire was administered to ascertain the type and extent of changes in contact lens wear and care since suffering from the CIE.

RESULTS

Slit-lamp biomicroscopy revealed the presence of a circular scar, approximately 1.5 mm in diameter, in the central cornea of the right eye of the patient who had suffered the most clinically severe CIE; no residual scar, or any other abnormality, was detected in any of the other 12 patients. No significant difference between the 2 eyes was found with respect to basal epithelial cell density; anterior or posterior keratocyte density; endothelial cell density, polymegethism, or pleomorphism; corneal thickness; or visual acuity. Anecdotally, however, markedly reduced pan-corneal cell counts, increased endothelial polymegethism, and reduced corneal thickness were observed in the affected eye of the patient who had suffered the most clinically severe CIE. After having suffered from a CIE, many patients changed lens type or brand, ceased to routinely sleep in lenses, or wore lenses less often.

CONCLUSIONS

In general, contact lens-associated CIEs do not compromise the long-term integrity of the cornea. Changes in lens-related behaviors of patients who have suffered from a CIE seem to be aimed at reducing the risk of a further occurrence. Anecdotally, more severe CIEs may be associated with chronic tissue morbidity.

Characteristics of and risk factors for contact lens-related microbial keratitis in a tertiary referral hospital

AIM

A retrospective case-control study was conducted at a tertiary referral hospital to determine the characteristics of and risk factors for contact lens (CL) related presumed microbial keratitis.

METHODS

Two hundred and ninety-one cases of presumed microbial keratitis were retrospectively identified over a 2-year period. Records were reviewed for a history of CL wear and, where identified, CL, demographic, and clinical data were collected. Lens wearing controls (n=186) were identified by a community telephone survey. Multiple logistic regression estimated risk factors for infection and vision loss.

RESULTS

Ninety-nine (34%) new cases of presumed microbial keratitis were associated with CL wear. Overnight soft CL use was associated with an increased risk of infection compared to daily disposable CL wear (odds ratio (OR): 8.03, 95% confidence interval (CI): 1.82-35.46). Compared with older CL wearers, 15-24 year olds had a 3.5 times greater risk of infection (OR, 95% CI: 1.7-7.4). Of the 84 cases with available data, 24 (29%) lost two or more lines of best-corrected visual acuity. Delaying treatment by 49-72 h had a 4.5 times (OR, 95% CI: 1.4-14.9) greater risk of visual loss compared to seeking treatment early. Of the 99 cases of infection, 88 were scraped and 78% (69/88) of these returned a positive culture. Gram-positive bacteria were the predominant causative organisms.

CONCLUSION

Overnight use of CL and youth carry a greater risk of infection. Practitioners should reinforce the importance of proper CL care at all times, and early presentation following the onset of symptoms.