Trends in contact lens-associated microbial keratitis in Southern India

OBJECTIVE: To review the microbiologic profile, clinical course, treatment, and outcome in patients with contact lens-associated microbial keratitis in the setting of a tertiary eye care center in a developing country in the Tropics. DESIGN: Retrospective noncomparative case series selected from an ongoing prospective series. PARTICIPANTS: Twenty-eight subjects examined in the contact lens clinic of L. V. Prasad Eye Institute, Hyderabad, south India, between February 1991 and September 2000, who presented with corneal stromal infiltrate on slit-lamp examination, were included in the study. INTERVENTION: All patients underwent standard diagnostic microbiologic evaluation and smear and culture-guided topical antimicrobial therapy. Penetrating keratoplasty was performed in some patients. MAIN OUTCOME MEASURES: Culture results and clinical response to antimicrobial therapy. RESULTS: Twenty eight (0.11%) of 23,889 contact lens-wearing patients presented with laboratory-proven infectious keratitis; this constituted 0.56% of 4967 corneal ulcer patients seen during the same period. Most (15/28) of the patients wore soft contact lenses on a daily basis. Rigid gas-permeable lenses were worn by six patients, therapeutic bandage contact lenses by four, and Silsoft lenses by four. Laboratory results showed bacterial infections in 25 patients (89.2%); Pseudomonas was the most common organism (13/25; 52%). Acanthamoeba, herpes simplex virus, and Aspergillus niger were isolated in one case each. Laboratory-based medical therapy led to the healing of ulcers in 24 (85.7%) of 28 patients, whereas 4 patients required penetrating keratoplasty. Most of the organisms were sensitive to antibiotics. CONCLUSIONS: Contact lens-associated microbial keratitis is rare in southern India. Soft contact lens wear is the most common risk factor; Pseudomonas keratitis is the predominant causative agent. Fungal, viral, and Acanthamoeba keratitis are rare. The offending bacteria are usually sensitive to antibiotics, and the treatment outcome with medical therapy is good.     

Risk factors and causative organisms in microbial keratitis

PURPOSE: To establish the risk factors, causative organisms, levels of antibiotic resistance, patient demographics, clinical presentations, and clinical outcomes of microbial keratitis at a tertiary hospital in Australia. METHODS: Patients who had a corneal scraping for culture over a 5-year period were identified through the local microbiology database, and a retrospective audit of their medical records was carried out. Clinical information was gathered from medical records, and smear, culture, and antibiotic resistance results were from the microbiology database. An index of disease severity was calculated for each patient from scores for the magnitude of the epithelial defect and anterior-chamber reaction and the location of the lesion. Associations between risk factors for keratitis and variables such as patient demographics, causative organism and antibiotic resistance, disease severity, and outcome were analyzed by using analysis of variance and chi tests with appropriate correction for multiple comparisons. RESULTS: Two hundred fifty-three cases of microbial keratitis in 231 patients were included. Sixty percent of patients were men, and there was a bimodal distribution in the age of presentation. Common risk factors for keratitis were contact lens wear (53; 22%), ocular surface disease (45; 18%), ocular trauma (41; 16%), and prior ocular surgery (28; 11%). Gram stains were positive in 33%, with a sensitivity of 53% and specificity of 89%. Cultures of corneal scrapings were positive in 65% of cases, and Pseudomonas aeruginosa (44; 17%), coagulase-negative staphylococci (22; 9%), Staphylococcus aureus (19; 8%), and fungi (7; 3%) were commonly recovered. P. aeruginosa was more common than other culture results in contact lens-related cases (55% vs. 0%-23%; P < 0.001), and S. aureus was more common than other culture results in ocular surgery-related cases (29% vs. 0%-21%; P < 0.001). Patients with keratitis related to prior ocular surface disease had more severe keratitis at the time of scraping (P = 0.037). Cultures positive for Fusarium, P. aeruginosa, and other Gram-negative organisms had statistically significantly more severe keratitis at the time of scraping, whereas patients with negative cultures had milder keratitis (P = 0.030). Only 2% of all bacterial isolates were resistant to ciprofloxacin, 20% of Gram-positive isolates were resistant to cephalothin, and no Gram-negative isolates were resistant to gentamicin. CONCLUSIONS: In this series, the most common risk factor for keratitis was contact lens wear and the most commonly isolated organism was P. aeruginosa.     

A case series of contact lens-associated Fusarium keratitis in Hong Kong

PURPOSE: To report the clinical features and management outcomes of a cluster of Fusarium keratitis in patients that used the Bausch & Lomb ReNu MostureLoc contact lens solution. METHODS: Retrospective case series. RESULTS: In a 1-year period starting from June 2005, we treated 12 patients with unilateral Fusarium keratitis in our tertiary care center. All patients were contact lens users that used ReNu MostureLoc contact lens solution and had no other specific predisposing conditions. Microbiological examination yielded growth of Fusarium spp. in 7 patients from corneal scrapings at presentation and from 3 patients in subsequent corneal specimens. For 2 other patients, fungi were not detected from corneal scrapings, but Fusarium spp. were isolated from their contact lenses. The infections were treated with topical natamycin and amphotericin B eye drops and with systemic itraconazole in 8 patients. The infection resolved with medical treatment in 8 eyes, a conjunctival flap in 1 eye, and a therapeutic corneal graft in 1 eye. Two eyes required tectonic corneal grafts for perforation. Two of the 3 corneal grafts failed because of graft rejection. Final visual acuities ranged from count fingers to 1.0. CONCLUSIONS: This cluster of Fusarium keratitis seems to be related to the use of the ReNu MoistureLoc contact lens solution. The cure rate with medical therapy was 66%. However, corneal scarring limited visual recovery. This episode highlights the need for clinical vigilance when dealing with corneal infiltrates in contact lens users.     

Referral pathways and management of contact lens-related microbial keratitis in Australia and New Zealand

Background: We examine the referral pathways and treatment for contact lens‐related microbial keratitis in Australia and New Zealand. Methods: Cases were reported in May 2003–September 2004; data on presentation, referral and treatment collected from practitioners and via patient interview. Severity was graded, 1‐week cure rate estimated, delays in treatment and medications documented. Hospital and private clinic managements were compared. Results: A total of 297 eligible cases were reported; detailed information on treatment and referral pathways was available on a subset of these cases. Presentation was to optometrists (81/200, 41%), general practitioners (GPs) (69/200, 34%) or emergency departments (46/200, 23%). Optometrists referred to private ophthalmologists (47/79, 60%) more often than hospitals (27/79, 34%). GPs initiated treatment (39/68, 57%) but also referred to hospitals (22/68, 32%) and to private ophthalmologists (7/68, 10%). Of all cases, 67% (195/297) were managed in hospitals (29% admitted, 87/297). Hospitalized cases were predominantly managed with fortified aminoglycoside/cephalosporin (66/81, 82%) and others fluoroquinolones (168/195, 86%). Steroids were used in 36% (98/276) commencing on day 5 (median, interquartile range = 3–7). One‐week cure rate was 60% (49/82) in private clinics, 72% (62/86) for hospital outpatient cases and 37% (25/67, P < 0.001) for inpatient cases, which were more severe diseases (47%, 52% and 0% mild, respectively). Delays (≥12 h) receiving therapy were experienced by 33% (55/168) because of initial inappropriate treatment (48/55), time delays (7/55) but not remoteness (P = 0.6). Conclusions: The majority of treatment is via hospital clinics, but milder disease is managed in private clinics. The referral process via optometrists, GPs and emergency departments is generally efficient; however, one‐third of cases experienced some delays before receiving appropriate therapy highlighting the need for timely diagnosis.     

Risk factors for contact lens-related microbial keratitis in Singapore

Purpose:

To investigate independent risk factors for contact lens-related microbial keratitis in Singapore and estimate their impact on disease load.

Methods:

Cases were contact lens wearers presenting to Singapore National Eye Centre with microbial keratitis between 2008 and 2010. Community contact lens wearers were recruited as controls. All wearers completed a previously validated questionnaire describing contact lens wear history, hygiene and compliance habits, and demographics. Risk factors significant in univariate analysis (P<0.2) were evaluated in a multivariate model.

Results:

In all, 58 cases of microbial keratitis and 152 contemporaneous controls were identified. When controlling for other variables, Chinese had a 7 × lower risk compared with other races (95% CI: 2.3–21.3, P=0.001). Those aged between 25 and 44 years were at 3 × increased risk compared with younger wearers (95% CI: 1.1–9.6, P=0.04). Occasional overnight contact lens wear (less often than one night per week) was associated with a 4 × higher risk (95% CI: 1.2–15.4, P=0.03) compared with daily use. Not washing hands before handling was associated with a 13 × increased risk (95% CI: 1.9–84.8, P=0.008). Use of multipurpose solution A carried a 16 × higher risk compared with hydrogen peroxide (95% CI: 1.5–174.0, P=0.02). The combined PAR% for modifiable risk factors (occasional overnight wear, not washing of hands, and MPS A) was 82%.

Conclusions:

Consistent with previous findings, independent risk factors for contact lens-related microbial keratitis include poor hand hygiene, occasional overnight wear, and type of lens care solution. Prolonged overnight or extended contact lens use was infrequent in this population.     

Impact of differences in diagnostic criteria when determining the incidence of contact lens-associated keratitis.

PURPOSE: The purpose of this study is to examine the effect of differences in within-study and between-study diagnostic criteria in determining the incidence of contact lens-associated keratitis. METHODS: We applied the sets of criteria for "microbial keratitis" as described in five previous studies to the dataset of Morgan et al., which documents 118 cases of contact lens-associated keratitis across a wide range of clinical severities. For each set of criteria, the incidence of contact lens-associated keratitis was calculated for the following five lens type/modality combinations: daily-wear rigid, daily-wear daily disposable hydrogel, daily-wear hydrogel, extended-wear hydrogel, and extended-wear silicone hydrogel. The effect of varying the clinical severity score for the differentiation of nonsevere versus severe keratitis was also examined with respect to the dataset of Morgan et al. RESULTS: The size and location of the corneal infiltrative events identified as representing "microbial keratitis" for each of the different sets of criteria are illustrated in a series of cartograms. A key between-study difference in the incidence values calculated for the various sets of criteria relates to the categories of extended-wear hydrogel and extended-wear silicone hydrogel lenses. Specifically, the incidence of "microbial keratitis" was found to be statistically significantly greater for extended-wear hydrogel compared with extended-wear silicone hydrogel lenses when the set of criteria of Morgan et al. was applied, but not when the other sets of criteria were applied, to the dataset of Morgan et al. Increasing the threshold clinical severity criterion for differentiating between nonsevere and severe keratitis within this dataset resulted in lower incidence values; however, such changes in threshold had a minimal impact on relative risk values. CONCLUSIONS: The choice of criteria for diagnosing contact lens-associated "microbial keratitis" has a significant impact on calculations of the incidence of this condition.     

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.     

Surveillance of contact lens related microbial keratitis in Australia and New Zealand: multi-source case-capture and cost-effectiveness

PURPOSE: To evaluate a multi-source surveillance system used in a 12-month study of contact lens related microbial keratitis in Australia and New Zealand. METHODS: All practicing ophthalmologists and optometrists were surveyed on 6 occasions over 12 months via post or the Internet. Participation was defined as reporting at least once during the study period and the response rates represented those who responded on all six occasions. Cases were also detected through hospital audit. All ophthalmologists and a sub-group of optometrists were contacted by phone to elicit a response (active surveillance). The utilization and cost-effectiveness of active surveillance were compared to reports received via the post or the Internet. Case ascertainment and cost-effectiveness were compared for different sources of case capture. RESULTS: The rate of participation for ophthalmologists was 95.8% (711/742) and 88.5% (657/742) responded for all reporting periods. Active surveillance was required for 63% (416/661) of responses in Australia (AU) and 73% (59/81) in New Zealand (NZ) at AUD23.14 per practitioner. Internet reporting was more widely used in New Zealand (NZ: 31% vs. AU:17%, p=0.006) and was the most cost effective mode of reporting (AUD1.43 per practitioner). Postal reporting (AUD; AU:3.54,NZ:9.84 per practitioner) was under-utilized (3% of responses). Average start-up costs comprised 50% of study costs followed by active follow-up (42%), postal (6%) and Internet reporting (2%). Ophthalmologists (50.4%, 144/286 of cases) were the most cost-effective source of cases, followed by hospital audit (24.5%, 70/286) and optometry (25.1%, 72/286). Duplicate reporting occurred in 13% (37/286) of cases. CONCLUSIONS: High response rates were obtained by substantial resource commitment to active follow-up. Internet reporting was widely used and was cost-effective. Hospital audit and supplementary reporting by optometry were used for the first time in a study of contact lens related microbial keratitis, and contributed significantly to case capture.     

Continuous wear silicone hydrogel contact lenses and microbial keratitis

Like other lens types, the new generation of silicone hydrogel contact lenses can be associated with a spectrum of ocular complications. Most tend to be very minor, but serious and sight-threatening complications can occur. We present four such cases with microbial keratitis following extended wear of these lenses. Cultures were positive for Pseudomonas aeruginosa in three cases and all three of these suffered lasting visual impairment. We describe our findings and discuss possible risk factors.     

Disposable contact lens use as a risk factor for microbial keratitis

AIMS—A case-control study was performed to evaluate soft contact lens (SCL) wear modality as a risk factor for microbial keratitis.
METHODS—Contact lens wearers presenting as new patients to Moorfields Eye Hospital accident and emergency department during a 12 month period completed a self administered questionnaire detailing demographic data and contact lens use habits. Cases were patients with a clinical diagnosis of SCL related microbial keratitis. Controls were SCL users attending with disorders unrelated to contact lens wear. Odds ratios (estimates of relative risks) and 95% confidence limits (CL) were calculated through multivariable logistic regression analysis.
RESULTS—There were 89 cases and 566 controls. A substantially increased risk with 1-4 weekly disposable SCL compared with non-disposable SCL was identified among both daily wear (DW) (odds ratio =3.51, 95% CL 1.60-7.66, p=0.002) and extended wear (odds ratio 4.76, 95% CL 1.52-14.87, p=0.007) users after adjustment for demographic, lens use and hygiene variables. Other significant factors among DW users were "occasional" overnight use, use of chlorine based (as opposed to other chemical) systems in combination with poor storage case hygiene, and irregular disinfection.
CONCLUSION—Properties of some disposable SCL may be partly responsible for these excess risks. It is also possible, however, that this finding is largely a reflection of widespread complacency among patients and practitioners with respect to disposable SCL fitting and use.

Keywords: microbial keratitis; disposable contact lenses     

Evaluation of surveillance methods for an epidemiological study of contact lens related microbial keratitis

PURPOSE: To evaluate surveillance methods in a pilot epidemiological study of contact lens related microbial keratitis (MK) cases identified by ophthalmic practitioners in Australia and New Zealand between May and August 2003 inclusive. METHODS: Twelve ophthalmologists and 55 optometrists from rural and metropolitan locations were sent a study information pack with postal reporting forms. After 2 months, practitioners were emailed a link to a website for Internet reporting. After 4 months, practitioners were prompted by email and then by telephone if a response was not received. Passive response rates were the rate of returns after posting information and emailing the website link. Active response rates included personalized email and telephone follow-up. RESULTS: Ten cases of MK were identified by optometrists and five by ophthalmologists. The passive response rates were 79% and 58% for the first and second reporting periods, respectively. There was a lower response rate in the second reporting period compared to the first (P = 0.02). With active surveillance the response rate increased to 97% and 96%. A large proportion of optometrists (62%) and ophthalmologists (55%) used the website for at least one reporting period. Internet reporting was used by all New Zealand practitioners (5/5). CONCLUSIONS: A surveillance study to estimate the incidence of contact lens related MK in Australia and New Zealand is feasible and acceptable. Internet-based reporting offers a reliable, rapid and cost-effective means of running a large scale, international surveillance study. Active surveillance methods are necessary to enhance reporting rates.     

Predisposing factors in microbial keratitis: the significance of contact lens wear.

Fifty-three patients consecutively admitted to Moorfields Eye Hospital for treatment of suspected microbial keratitis were examined to identify predisposing factors. The principal associations were pre-existing corneal disease (22 patients (41.5%] and contact lens wear (22 patients (41.5%]. In 13 cases (25%) contact lens wear was the only factor in patients with otherwise healthy eyes using contact lenses as an alternative to spectacles. Gram-negative keratitis was more frequent in the lens wearers, with the exception of therapeutic lens users, than in other patients (p = 0.0006) and Pseudomonas aeruginosa caused keratitis in cosmetic soft lens users more frequently (p = 0.001). There was no correlation between lens handling or solution contamination in three extended wear soft-lens users. This implies that some soft-lens wearers may be infected by Gram-negative organisms from environmental sources other than contaminated lens care materials. Gram-negative keratitis is strongly associated with contact lens wear, and the diagnosis must be considered in any contact lens user with an acutely painful red eye.