Since the first contact lenses (CLs) were made in the 19th century, CLs have been continuously developed.1 Due to the benefits of larger diameter, higher oxygen transmissibility, greater thickness, and more sustainable overnight wearing, bandage CLs (BCLs) have widely replaced conventional lenses and act as bandage for the treatment of many ocular surface conditions, such as corneal epithelial defects, corneal perforations, ocular chemical burns, and dry eye syndrome, because they can tamponade corneal wounds, relieve surface generated pain, and promote corneal epithelial regeneration.2–5 Currently, BCLs are being applied after several types of eye surgeries, such as keratoplasties, corneal collagen cross-linking (CXL), pterygium surgery, and laser in situ keratomileusis. Recent studies have reported that 20.8% of cases experienced corneal infection after wearing CL. Also, BCLs cannot eliminate the risk of infectious keratitis.6–8 In 1984, a study by Galentine et al.9 found 10% to 12% of patients developed microbial keratitis after wearing traditional BCLs. With the development of materials and the manufacturing method, the risk of infectious keratitis with BCLs has greatly decreased. In 2013, Saini et al.10 reported BCLs had a 2.9% incidence of microbial keratitis.
Previous studies also reported some contributing factors for the incidence of infectious keratitis with BCLs. Bandage CLs are prescribed for daily wear or up to 30-day extended wear. Although most patients successfully wear BCLs, the prolonged use of BCL and wear overnight had a greater risk than daily wear. Furthermore, prophylactic antibiotic use cannot eliminate the risk of infectious keratitis.10,11 Although early studies have reported a great effect on silicone hydrogel BCLs, they are prone to bacterial adhesion11 (Bandage Lenses in the Postoperative Care for Cataract Surgery Patients: A Substitute for Eye Patch?). However, a large-scale study of BCL-associated complications has not yet been conducted, and it is not clear which potentially contributing factors may be associated with BCLs. Therefore, the aim of this study was to investigate the clinical characteristics of infectious keratitis related to BCL use.
MATERIALS AND METHODS
This was a retrospective study conducted in compliance with the principles expressed in the Declaration of Helsinki. In addition, this study was approved by the ethics committee of the Second Affiliated Hospital at the Zhejiang University School of Medicine in China. The clinical features of the patients diagnosed with BCL-related infectious keratitis were reviewed at the eye center of the Second Affiliated Hospital at the Zhejiang University School of Medicine from January 2015 until August 2018. Detailed information about the patients who developed infectious keratitis was collected, including the age, gender, clinical characteristics, culture results, and other measures. All the patients were fitted with silicone hydrogel BCLs (PureVision; Bausch+Lomb, Bridgewater, NJ or SureSight; Alcon, Fort Worth, TX) for continuous wear. The parameters of PureVision included water content 36%, oxygen transmissibility 112 Dk/t, base curve 8.3 mm, diameter 14.0 mm, and thickness 0.05 mm. The parameters of Sure Sight included water content 24%, oxygen transmissibility 131Dk/t, base curve 8.4 mm, diameter 13.8 mm, and thickness 0.05 mm. The choice between the two BCL brands was a shared decision made by both the ophthalmologists and patients.
The infectious keratitis diagnosis was made using the patient's history, clinical findings, confocal biomicroscopy results, and ulcer cultures. In this study, the definition of persistent corneal epithelial defects included persistent epithelial defects, recurrent corneal epithelial erosion, and ocular surface chemical injuries. The suggested BCL wearing time after the CXL and pterygium surgeries was 1 week, whereas the recommended postkeratoplasty time was not more than 28 days. The suggested wearing time for persistent corneal epithelial defects varied from 1 to 4 weeks. All the patients received 0.5% levofloxacin eye drops as a preventive medication to be applied 4 times per day. The other management protocols varied according to the primary disease. The patients were followed up each week while they were wearing the BCLs.
The general data were expressed as the mean±SD using IBM SPSS Statistics for Windows version 24.0 (IBM Corp., Armonk, NY). The significance of the BCL potential risk factors was determined using the χ2 test of independence for proportions. The differences were considered to be statistically significant at a P value <0.05.
During the time period of this study, 6,685 eyes of 6,188 patients, including 3,410 (54.9%) males and 2,788 (45.1%) females, received BCLs. The patients' mean age was 49.5±19.8 years (range=15–78 years). The mean BCL wearing time was 19.8±23.7 days (range=1–58 days). Overall, 3 patients complained of serious discomfort on the first day after the BCL fitting, and those BCLs were removed immediately. In addition, 8 patients lost their BCLs from 1 to 3 days after they began wearing them. With regard to the brand names, 3,300 of the lenses were PureVision lenses and 3,385 of them were SureSight lenses.
The clinical features of the patients with infectious keratitis are shown in Table 1. Infectious keratitis was diagnosed in 8 eyes of 8 cases (0.13%), and the mean age of those patients was 50.80±21.92 years (range=16–75 years). Seven of the patients were older than 50 years, and 1 patient was 16 years old. The infectious keratitis incidence rate in the older patients (≥50 years) was significantly higher than that in the young patients (<50 years) (χ2=9.647, P=0.002). The mean infectious keratitis diagnosis time was 19.40±23.35 days (range=3–58 days) after wearing the BCLs. Among these 8 infectious keratitis patients, 3 were noncompliant with their eye drop use and 2 extended the wearing period over 30 days, including 1 patient who continuously used one of the BCLs for 58 days without any eye drops.
The most common BCL indication was a persistent corneal epithelial defect (n=4,066, 60.8%), followed by pterygium surgery (n=1813, 27.1%), keratoplasty (n=454, 6.8%), and CXL (n=352, 5.3%). There was a higher postkeratoplasty risk of BCL-related infectious keratitis than in the corneal epithelial defect (χ2=21.371, P=0.000) and pterygium surgery (χ2=16.037, P=0.000) cases, but not after a CXL (χ2=1.792, P=0.181) (Table 1).
When infectious keratitis was suspected, the BCLs were removed immediately. Based on the cultures of the scrapings of these 8 infected corneas, 2 were positive for Fusarium oxysporum, 2 were positive for Streptococcus pneumoniae, and 1 was positive for Staphylococcus aureus. However, all the cultures from the BCLs that were removed were positive (Table 2). The patients with the F. oxysporum infection were treated with antifungal medication (topical natamycin eye drops and oral itraconazole), whereas the bacterial keratitis cases were treated with topical antibiotics (intensive 0.5% levofloxacin topical eye drops). Of these eight cases, seven subsequently underwent additional surgical interventions, such as a lamellar keratoplasty or penetrating keratoplasty.
Bandage CLs, when worn and cared for properly, are a safe and effective form of corneal wound protection that relieves surface-generated pain and promotes corneal epithelial regeneration. However, BCL wearers are at risk of CL-related eye infections, especially when the wearers do not practice proper CL wear and care habits. Microbial keratitis associated with bandage CL use can lead to serious adverse visual and health outcomes. In this study, we found that noncompliance with the doctor's advice, such as not using eye drops while wearing the BCLs and overusing the BCLs, might be the most important reason for BCL-related infectious keratitis. These results were consistent with those from a previous report.7 Although the compliance behavior data are incomplete, education is important for increasing patient compliance.
This case series of BCL-related corneal infections highlights the risks patients wearing BCLs face. A review by Alipour et al.12 reported that the incidence of CL-related microbial keratitis was 2 per 10,000 lens wearers each year. In addition, previous epidemiological studies have reported that the approximate yearly incidence of CL-related microbial keratitis was 3 to 5 per 10,000 individuals.9 In our study, the BCL-related infectious keratitis incidence (0.13%) was higher than that of CL-related microbial keratitis. This difference in infection incidences could be attributed to the differences in the indications and wearing times of the BCLs. Bandage CLs are used mainly for treating ocular surface diseases, whereas CLs are commonly used for treating refractive errors.
Our findings showed a higher rate of infection in those patients who wore BCLs after undergoing keratoplasties. This was probably associated with the nature of the corneal surgery. According to different studies, the incidences of postkeratoplasty corneal infections range from 1.76% to 12.6%.10 In addition, ultraviolet light exposure is associated with an increased risk of infectious keratitis after undergoing a CXL.13,14 Moreover, biofilm formation and the lipids and large protein amounts from tears that are deposited on CLs increase the risk of postoperative infections. There is also a positive correlation between the wearing time and the risk of CL-related infectious keratitis.15,16 One interesting finding reported by some previously published studies was that granular corneal dystrophy (GCD) patients are prone to postkeratoplasty corneal infections,17,18 which might explain why the GCD patient in this study developed infectious keratitis with BCL use. In our study, infectious keratitis was not observed after the pterygium surgeries, which was consistent with other studies.19 The potential reasons for the lack of BCL-related infectious keratitis after a pterygium surgery may be due to the minor corneal wounds and normal corneal epithelial basement membrane. Our results suggested that the greatest risk factor for BCL-related infectious keratitis was postkeratoplasty use. Therefore, ophthalmologists should take more care and pay close follow-up attention to BCL wearers after they perform keratoplasties.
Many studies have reported that a young age was related to CL-related microbial keratitis. However, Lim et al.20 reported a higher risk in CL wearers between the ages of 25 and 44 years when compared with younger wearers. In this study, BCL-related infectious keratitis was identified in 8 patients, including 7 who were older than 50 years. Only one of those patients was young (16 years old). The infectious keratitis incidence rate in the older patients (≥50 years) was significantly higher than that in the younger patients (<50 years). These results suggest that an older age could be linked to an increased risk of BCL-related infectious keratitis. Many other studies have shown that aging is associated with a decline in tissue and organ functions.21–23
Gender was not identified as a significant risk factor in our study. However, a previous study showed that males were prone to CL-associated complications.21 The results of the study by Mohammadpour et al.7 were consistent with our results. Due to the retrospective nature of our study, it was hard to analyze the BCL-wearing modalities and other factors.
The positive culture incidences reported in the literature varied from 10.63% to 14% in the previous CL studies.24 One study by Lin et al.25 reported that Pseudomonas aeruginosa was the dominant organism found in their CL-related keratitis cases.26,27 However, fungi have been reported as the dominant organisms in CL-related keratitis in other countries. In addition, Staphylococcus epidermidis was the most commonly isolated microorganism from the contaminated BCLs in another study.28 In this study, all the cultures from the BCLs removed from the eight patients suspected of having infectious keratitis were positive, along with five of the scraping cultures. The culture results showed that both fungi and bacteria can be found in infectious keratitis patients wearing BCLs. The different microbial infections found in different studies may be related to the living circumstances of the patients, the BCL indications, and the BCL management.
Despite relatively low incidence of infectious keratitis, it is a serious complication related to BCL use. It is more likely to occur in older patients, and the greatest risk factor for BCL-related infectious keratitis is postkeratoplasty use. Moreover, refusing to obey the doctor's orders with regard to BCL use, such as not using eye drops and overusing the BCL, may be an important cause of BCL-related infectious keratitis. Wearing CLs while sleeping has been shown to be a risk factor, regardless of the lens material and frequency, with even occasional overnight use conferring a risk.28,29 Although BCLs have been approved by the US Food and Drug Administration for overnight wear, the increased risk of infection has been acknowledged by their classification as a class 3 medical device. Therefore, appropriate indications, good compliance, and close follow-up attention are required for BCL use, and ophthalmologists should pay close attention to the early signs of infection.
This study was funded by National Natural Science Foundation of China (Grant No. 81270974;81870624;81700802), Major science and technology projects of zhejiang province (grant No.2017C03046).
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