Contact lens-related microbial keratitis: how have epidemiology and genetics helped us with pathogenesis and prophylaxis

Contact lens wear is a common predisposing factor in microbial keratitis and is one of the two preventable risk factors for corneal infection in a working age population. Our understanding of the prevention and prophylaxis of contact lens-related corneal infection is informed by recent epidemiological studies describing the incidence of and risk factors for the disease, the effect of causative organism on disease severity, and an appreciation of individual immune profiles in susceptibility to and severity of the disease. Although contemporary contact lenses have not reduced the overall incidence of keratitis, a reduction in morbidity may be achievable through recognition of appropriate risk factors in severe disease, including avoiding delays in presenting for appropriate treatment, and attention to storage case hygiene practise. Severe keratitis is most commonly associated with an environmental causative organism, and daily disposable lenses are associated with less severe disease. Pseudomonas aeruginosa remains the commonest cause of contact lens-related corneal infection probably because of its unique virulence characteristics and ability to survive in the contact lens/storage case/ocular environment. In two recent outbreaks of contact lens-related infections, there has been a strong association demonstrated with particular contact lens solutions. Since the recall of these specific contact lens solutions, the rate of Acanthamoeba keratitis has remained above the expected baseline, indicating unidentified risk factors that may include environmental exposures. Individual differences in susceptibility to microbial keratitis may be partly explained by differences in single-nucleotide polymorphisms in certain cytokine genes, particularly those with a proven protective role in corneal infection.     

Adherence of Acanthamoeba castellanii cysts and trophozoites to unworn soft contact lenses

Contact lens-related Acanthamoeba keratitis has been associated with the use of soft contact lenses and homemade saline solutions. We studied the adherence of Acanthamoeba to unworn extended-wear soft contact lenses on a human corneal isolate of Acanthamoeba castellanii suspended in normal saline (cysts, 6.3 x 10(5)/ml; trophozoites, 3.6 x 10(5)/ml). Unworn hydrogel contact lenses (polymacon, water content 38.6%; 50 lenses, 400 lens segments) were exposed to A. castellanii cysts or trophozoites with or without stirring. After exposure for zero to seven hours, soft contact lenses were or were not washed, and the A. castellanii adherence was determined with a standardized light-microscopy technique (40 fields, ten lens segments for each count) and with scanning electron microscopy. Both cysts and trophozoites adhered to the unworn soft contact lenses. Trophozoites showed acanthopodia, lobopodia, and filopodia. This study indicates that both A. castellanii cysts and trophozoites can firmly adhere to unworn soft contact lens. Such adherence may play a role in the pathogenesis of soft contact lens-related Acanthamoeba keratitis.     

Infectious keratitis: correlation between corneal and contact lens cultures.

PURPOSE: This article reports a study of the effectiveness of performing contact lens cultures to identify causative organisms of infectious keratitis in patients using extended-wear soft contact lenses (cosmetic or therapeutic). METHODS: Patients' records from the Ocular Microbiology Laboratory of the Department of Ophthalmology, Paulista School of Medicine, from 1976 to 2000, and data of patients with contact lens-related keratitis in which the contact lens had been cultured were collected and reviewed. RESULTS: One hundred thirteen patients were included. Only soft contact lenses had been cultured and 29.2% of them were therapeutic contact lenses. An overall concordance of 84.0% was found between cultures obtained from corneal scrapings and contact lenses, with a higher rate in fungal keratitis (100%) compared to amebic (80.0%) and bacterial (74.5%) keratitis. In cases of concomitant bacterial growth in cultures of scrapings and contact lenses, the same organism was detected in 97.04%. Most cases of bacterial infection were caused by Pseudomonas spp. Among the discordant cases (16%), a microorganism was more likely to be isolated by contact lens culture (94.4%). CONCLUSION: Contact lens cultures may identify the causative organisms in most cases of contact lens-related keratitis. The clinical relevance of positive contact lens cultures in keratitis with negative corneal cultures needs further investigation.     

Invasion of the therapeutic contact lens by a rare fungal species presenting as the acute red eye: A case report

Therapeutic contact lens used in the treatment of non-infective corneal pathologies are prone to infection by microorganisms like bacteria, protozoa and fungi. Bacteria cause the majority of contact lens-related infections. Although rare, fungal invasion of soft contact lenses is a potentially severe complication which may cause keratitis and more fulminating infections. Contact lens invasion can present as acute red eye warranting its replacement to prevent the development of keratitis. Different genera and species of fungi are documented to cause contact lens invasion. We report a rare case of fungal invasion of the contact lens by Aspergillus nidulans.     

Contact lens complications

Complications associated with contact lenses range from mild to severe and occur with all lens modalities. Contact lens wear can cause a change in corneal physiology, which can lead to epithelial, stromal, and endothelial compromise. Other complications include lens deposition, allergic conjunctivitis, giant papillary conjunctivitis, peripheral infiltrates, microbial keratitis, and neovascularization. Pre-existing conditions can contribute to these complications, or they can occur in association with contact lens wear and care regimens. Patient-related factors, such as alteration of the recommended wearing or replacement schedules and noncompliance with recommended contact lens care regimens for economic reasons, convenience, or in error, contribute to contact lens-related complications and have led to difficulty in accurate determination of complication rates among the various lens wear modalities. Complications may require discontinuation of contact lenses, topical therapy, and changes in contact lens wearing schedules, materials, and care solutions. On initial lens fitting and follow-up evaluations, practitioners should review contact lens replacement and cleaning regimens with patients and discuss complications. To avoid serious complications, patients should be reminded to remove their contact lenses as soon as ocular irritation occurs, and to call their eye care practitioner immediately if symptoms persist.     

Treatment, material, care, and patient-related factors in contact lens-related dry eye

PURPOSE: To examine the effect of general contact lens and material characteristics, care solutions, treatment, and patient-related factors on contact lens-related dry eye. METHODS: The data were derived from the Contact Lens and Dry Eye Study, designed as a cross-sectional and nested case-control study including 360 subjects. In separate statistical models, logistic regression was used to examine general contact lens characteristics, specific hydrogel lens materials, care solutions, and patient-related factors associated with dry eye status (controlled for age, gender, and current treatments). RESULTS: Several factors were significantly associated with dry eye, including treatment factors such as a recent contact lens refitting (odds ratios [OR] = 5.75, 95% confidence intervals [CI] = 2.14 to 15.46) and use of artificial tears/rewetting drops (OR = 1.09, 95% CI = 1.02 to 1.16), in addition, currently worn materials including Food and Drug Administration (FDA) group II (OR = 2.98, 95% CI = 1.14 to 6.19) and IV (OR = 1.87, 95% CI = 1.08 to 3.24). Significant patient-related factors included decreased overall satisfaction (OR = 3.57, 95% CI = 2.08 to 5.88,), dry eye in the absence of contact lens wear (OR = 6.54, 95% CI = 2.57 to 16.62), reduced daily lens wear duration (OR = 1.16, 95% CI = 1.06 to 1.26), and reduced ability to wear lenses as long as desired (OR = 2.44, 95% CI = 1.30 to 4.54). Care solutions were not associated with contact lens-related dry eye. CONCLUSIONS: The strong association of common treatment factors with dry eye status in contact lens wearers suggests that these treatments are not entirely effective. The use of high water content materials was strongly related to dry eye in lens wearers, whereas care solutions were not. Contact lens-related dry eye was also associated with several patient-related factors such as greater ocular discomfort (without lenses), dissatisfaction, and inability to wear lenses for desired durations.     

Contact lens-related corneal infection in Australia

Microbial keratitis is a rare but potentially severe sight-threatening condition, associated with societal burden, cost and morbidity. Compared with microbial keratitis without lens wear, the disease in contact lens wear is more common, occurs at an earlier age, has lower morbidity and is more often caused by Pseudomonas aeruginosa and Acanthamoeba spp. Resistance to common antibiotics is infrequent in contact lens-related isolates and there is little evidence to suggest increasing bacterial resistance over time. There is some evidence for increased reporting of cases of Acanthamoeba keratitis internationally. The incidence of contact lens-related microbial keratitis has remained stable over time. Rates vary with wear modality, with the lowest risk of severe disease in daily disposable and rigid gas permeable contact lens wear; however, there are limited studies in daily wear silicone hydrogel and in contemporary daily disposable contact lenses. Risk factors for contact lens-related microbial keratitis can be either modifiable or non-modifiable and interventions to reduce the risk of, or severity of disease may be prioritised based on the attributable risk. Key risk factors based on high attributable risk include any overnight wear, failing to wash and dry hands prior to handling lenses and poor storage case hygiene practice. The strong link between microbial keratitis and storage case hygiene and replacement suggests the relevance of microbial contamination of the storage case. Both risk factors and evidence-based strategies for limiting storage case contamination are presented, including storage case cleaning protocols and antimicrobial storage cases; however, it is unclear if such interventions can ultimately limit the rate or severity of microbial keratitis in daily wear. Emerging challenges include understanding and limiting the risk of infection associated with decorative or cosmetic contact lens wear, particularly in Asia, and in understanding the safety of contact lens modalities for myopia control in a paediatric population     

Acanthamoeba keratitis. A growing problem in soft and hard contact lens wearers

Eleven contact lens-wearing patients presented with Acanthamoeba keratitis. Eight cases were culture- and/or stain-positive for Acanthamoeba and three were presumed to have Acanthamoeba keratitis based on history and clinical findings. Six wore daily wear soft contact lenses, two wore extended-wear soft contact lenses, one wore a polymethylmethacrylate hard contact lens, one wore a gas-permeable hard contact lens, and one wore a Saturn lens (combined hard and soft lens). Four patients used distilled water and salt tablet saline, three used tap water and salt tablet saline, two used tap water rinse, two used well water rinse or storage, and one used intravenous (IV) saline. It is apparent that all contact lens wearers are at some risk for Acanthamoeba keratitis developing if proper contact lens care is not maintained. Of great concern is the inability of most current chemical sterilization methods to kill the organism if the lens becomes contaminated. Heat disinfection will kill Acanthamoeba trophozoites and cysts but the lens must not be placed into contaminated solutions afterward. Prevention is very important because medical and surgical treatment failures are frequent. Eye care practitioners who fit contact lenses are advised to use heat disinfection for low-water content stock soft contact lenses, and to use hydrogen peroxide without a catalyst for a minimum of 6 hours for all other stock lens fitting sets, to specifically inquire about contact lens care habits used by their patients, and to discourage the use of homemade saline solutions.     

First contact diagnosis and management of contact lens-related complications

To describe the spectrum of contact lens-related problems in cases presenting to a tertiary referral eye hospital. A retrospective case record analysis of 111 eyes of 97 consecutive patients was undertaken over a period of five months at the Royal Victorian Eye and Ear Hospital, Melbourne, Australia. Contact lens-related complications (CLRC) were classified into microbial keratitis, sterile corneal infiltrates, corneal epitheliopathy and contact lens-related red eye (CLARE). Main parameters examined were nature of the first contact, clinical diagnosis, and management pattern. Forty-two percent of the initial presentations were to health care practitioners (HCPs) other than ophthalmologists. Mean duration from the onset of symptoms to presentation was 6.3 ± 10.9 days. Forty-nine percent (n = 54) of patients had an associated risk factor, most commonly overnight use of contact lenses (n = 14, 13 %). Most common diagnosis at presentation was corneal epitheliopathy (68 %) followed by sterile infiltrates (10 %), CLARE (8 %) and microbial keratitis (6 %). No significant differences were found in the pattern of treatment modalities administered by ophthalmologists and other HCPs. HCPs other than ophthalmologists are the first contact for contact lens-related problems in a significant proportion of patients. These HCPs manage the majority of CLRC by direct treatment or immediate referral.     

Severe corneal infections associated with contact lens wear

An analysis of acute contact lens-related complications, with particular emphasis on severe microbial keratitis, was undertaken at the Department of Ophthalmology, Sahlgren's Hospital in Gothenburg. A total of 224 contact lens wearers presented with acute complications over a 2-year period (1981-1982). The lowest incidence of acute complications was found with hard contact lens wear. Similar numbers of daily wear and extended wear soft contact lens wearers presented with acute complications. The highest incidence of severe microbial keratitis was found in patients wearing soft contact lenses on an extended-wear basis. Inappropriate topical steroid therapy was implicated as a major factor contributing to the severity of these cases. Less severe sequelae of contact lens-related complications were also over-represented in the extended lens wear group. These findings emphasize the need for a conservative approach to the use of an extended wear regimen with soft contact lenses.     

角膜接触镜与视觉质量的研究进展与评价

角膜接触镜配戴的目的不仅是为了美观、方便和增视，同时还能提高视觉质量。人们对视觉质量的要求促进了角膜接触镜在材料、设计和功能上的发展。对角膜接触镜相关视觉质量问题的理解和研究，可以促使角膜接触镜在临床应用上发挥更大作用。     

Contact lens-related corneal ulcers in compliant patients

PURPOSE: To report a case series of contact lens-related corneal ulcers in compliant patients with no apparent predisposing factors. DESIGN: Retrospective case series. METHODS: Charts of 70 patients with contact lens-related corneal ulcers from July 1999 to June 2002 were reviewed. Lens care hygiene and method of disinfection, as well as frequency of lens replacement, were recorded. Only patients who followed recommended guidelines for contact lens wear were included in the study. RESULTS: Of the 70 patients, 21 (30%) developed corneal ulcers despite being compliant with the guidelines for contact lens wear. All patients used multipurpose solutions for cleaning, disinfecting, and storing daily wear soft contact lenses. CONCLUSION: Standard lens care hygiene does not seem to be sufficient in preventing the development of corneal ulcers in patients using conventional and frequent replacement daily wear soft contact lenses.     

Relationship between climate, disease severity, and causative organism for contact lens-associated microbial keratitis in Australia

PURPOSE: To evaluate associations between disease severity, causative organism, and climatic variation in contact lens-related microbial keratitis in Australia. DESIGN: Prospective, observational case series. METHODS: Contact lens wearing patients (n = 236) with presumed microbial keratitis presenting to private and hospital ophthalmologists in Australia between October 1, 2003 and September 30, 2004 were identified prospectively. Clinical details, management information, and microbiology data were collected and cases were graded for severity based on lesion size and location criteria. Causative organisms were assigned to "environmental" or "endogenous" groups. Climate zone and daytime temperature and humidity were determined for the geographic location of each event. The main outcome measures were disease severity, causative organism, and climate zone. RESULTS: Severe contact lens-related microbial keratitis was more likely to occur in warmer, humid regions of the country (P < .001), compared with smaller, increasingly peripheral corneal lesions that were more common in cooler conditions (P < .001). Culture-proven keratitis was predominantly caused by environmental organisms with Pseudomonas aeruginosa being recovered most frequently. Environmental organisms were isolated more commonly from tropical regions of the country and also accounted for nearly all cases of vision loss that occurred during the study period. Humidity did not have a significant effect on causative organism. CONCLUSIONS: Climatic conditions play a role in disease severity and causative organism in contact lens-related microbial keratitis and therefore have implications for practitioners involved in contact lens care and contact lens wearers who live in or travel to the tropics.     

Health belief and health practice in contact lens wear--a dichotomy?

PURPOSE: To establish if the hygiene practice of contact lens wearers (CLWs) can be influenced by "health belief." METHODS: A nested case-control study based on questionnaires was conducted in Hong Kong over a 17-month period between 45 CLW patients with microbial keratitis and 135 matched asymptomatic CLW volunteer controls. RESULTS: There was no significant difference between keratitis patients and controls (volunteers) in the perceived benefits of optometrists' instructions generally. When asked specifically, however, keratitis patients scored significantly higher than controls in the perceived benefit of checking initially with the optometrist for the correct method of lens cleaning. Contact lens wearing patients with keratitis were confident that their care of lenses would prevent complications, but this probably represented over confidence in themselves. Patients also scored significantly more neutrally in self-efficacy. Surprisingly, patients were significantly less likely to perceive the cost of lens care as a barrier but did not use their disinfecting regimes properly. CONCLUSION: We have found that CLWs still regard their eye care professional as being the most important for giving them advice on hygiene. There is considerable opportunity to educate and influence CLWs in ways to prevent infection, but the advice given must be correct. Continuing education of optometrists is also required.     

Ulcerative keratitis associated with contact lens wear

From October 1982 through June 1986, 658 patients developed ulcerative keratitis. In 196 of these patients it was contact lens-related. Fifty-nine patients wore extended-wear contact lenses for cosmetic purposes. On culture, Pseudomonas species was the organism most frequently isolated from the ulcers associated with contact lens wear. No cases of fungal keratitis were found in the contact lens group as compared to 40 cases (17%) in the noncontact lens group. Compared to results of a similar study covering January 1977 through September 1982, current results showed a larger number of patients using extended-wear lenses for cosmetic reasons (59 vs one) and overall younger age.     

Keratitis with Elizabethkingia meningoseptica Occurring after Contact Lens Wear: A Case Report

To report keratitis with Elizabethkingia meningoseptica, which occurred in a healthy patient after wearing contact lenses for 6 months. A 24-year-old male patient visited our hospital with ocular pain. This patient had a history of wearing soft contact lenses for 6 months, about 10 hours per day. At initial presentation, slit lamp examination showed corneal stromal infiltrations and small epithelial defect. Microbiological examinations were performed from corneal scrapings, contact lenses, and the contact lens case and solution. The culture results from contact lenses, contact lens case and solution were all positive for Elizabethkingia meningoseptica. Thus, we could confirm that the direct cause of keratitis was contamination of the contact lenses. The patient was treated with 0.3% gatifloxacin. After treatment, the corneal epithelial defect was completely healed, and a slight residual subepithelial corneal opacity was observed. We diagnosed keratitis with Elizabethkingia meningoseptica in a healthy young male wearing soft contact lenses. We conclude that Elizabethkingia meningoseptica should be considered as a rare but potential pathogen for lens-related keratitis in a healthy host.     

Microbiology of contact lens-related keratitis

We reviewed 397 cases of microbial keratitis examined at the Massachusetts Eye and Ear Infirmary, Boston, MA, U.S.A., from January 1982 through December 1985. Of these, 136 cases (34%) were related to contact lens use. Extended-wear contact lenses were used by 107 (79%) of these patients. Cosmetic contact lenses accounted for 59 (44%) of lens-related cases, aphakic contact lenses 44 (32%), and therapeutic (bandage) contact lenses 33 (24%). Fifty-three microbial keratitis cases associated with contact lens wear were culture-positive: 28 (52%) were gram-positive, and 19 (36%) were gram-negative. Mixed cultures, fungi, and Acanthamoeba accounted for two cases (4%) each. Pseudomonas aeruginosa was specifically associated with cosmetic soft contact lens use.     

Acanthamoeba keratitis and contact lens wear

Acanthamoeba keratitis is a rare but serious complication of contact lens wear that may cause severe visual loss. The clinical picture is usually characterised by severe pain, sometimes disproportionate to the signs, with an early superficial keratitis that is often misdiagnosed as herpes simplex virus (HSV) keratitis. Advanced stages of the infection are usually characterised by central corneal epithelial loss and marked stromal opacification with subsequent loss of vision. In this paper, six cases of contact lens‐related Acanthamoeba keratitis that occurred in Australia and New Zealand over a three‐year period are described. Three of the patients were disposable soft lens wearers, two were hybrid lens wearers and one was a rigid gas permeable lens wearer. For all six cases, the risk factors for Acanthamoeba keratitis were contact lens wear with inappropriate or ineffective lens maintenance and exposure of the contact lenses to tap or other sources of water. All six patients responded well to medical therapy that involved topical use of appropriate therapeutic agents, most commonly polyhexamethylene biguanide and propamidine isethionate, although two of the patients also subsequently underwent deep lamellar keratoplasty due to residual corneal surface irregularity and stromal scarring. Despite the significant advances that have been made in the medical therapy of Acanthamoeba keratitis over the past 10 years, prevention remains the best treatment and patients who wear contact lenses must be thoroughly educated about the proper use and care of the lenses. In particular, exposure of the contact lenses to tap water or other sources of water should be avoided.     

Contact lens-related deep stromal intracorneal hemorrhage.

Deep corneal neovascularization is a recently described complication of contact lens wear. Visual loss associated with deep corneal neovascularization has been associated with stromal lipid leakage. Deep intracorneal hemorrhage is rare and has been documented infrequently with the use of contact lenses. The authors present five cases of deep stromal hemorrhage associated with contact lens-related deep corneal neovascularization. These patients had no other discernible cause for their vascularization and subsequent hemorrhage. One patient required a penetrating keratoplasty for visual rehabilitation. Contact lenses of all types may cause neovascularization. The deep stromal neovascularization develops insidiously and may progress in the absence of acute symptoms. The presence of deep stromal neovascularization must be watched carefully and managed as a potentially vision-threatening complication of contact lens use.     

Trends in contact lens-related corneal ulcers

PURPOSE: To analyze the frequency of contact lens-related corneal ulcers and its relationship to the type of contact lens and care. METHODS: Charts of 376 patients with corneal ulcers seen at the Cornea Service of Wills Eye Hospital from July 1, 1999 to December 31, 2002 were retrospectively reviewed. All patients with contact lens-related corneal ulcers were identified, and information regarding cultures, lens type, usage, and cleaning was obtained. RESULTS: Of the 376 cases, 113 (30%) were related to contact lens use. The contact lens history was recorded in 83 of 113 cases (73%). The soft daily wear frequent replacement lens was the most common lens type associated with corneal ulcers (n = 36/83, 43%). Corneal cultures were performed in 71 of 113 cases (63%) and were positive in 51 of 71 cases (72%). The most common microorganism involved was Pseudomonas aeruginosa (n = 17/51, 33%). The frequency of contact lens-related corneal ulcers from 1999-2002 (n = 113/376, 30%) was significantly greater than that from years 1996-1999 (n = 37/299, 12%) at our institution (P < 0.05). CONCLUSION: There was a significant increase in the number of contact lens-related corneal ulcers between 1999 and 2002 compared with previous years (P < 0.05). The contact lens type most frequently associated with corneal ulcers was the soft daily-wear frequent-replacement contact lens (43%). Contact lens-related corneal ulcers continue to be a serious problem despite a shift in the market to the use of frequent-replacement daily-wear contact lenses and advances in contact lens technology.