Contact lenses. 2: Contact lens associated infections

Contact lens wearers, especially those who wear soft or extended wear contact lenses, are at increased risk of suffering from keratitis. Among the causes of corneal infections, an inadequate hygiene or overextended wear play an important role. An insufficient cleaning and disinfection leads to contamination with pathological germs. Sites of entry for these germs are corneal microlesions, caused by the setting and removal of contact lenses, and epithelial defects, as a result of the wearing of old or defective contact lenses. Primary eye diseases of patients who wear contact lenses can be altered by their wearing, and vice-versa. Even more, miscellaneous infections may lead to infectious corneal ulcerations. Having an adequate hygiene, a proper patient orientation during the medical visit, and a regular control are therefore of great importance for the reduction in the frequency of such infections by patients who wear contact lenses.     

Early clinical diagnosis of acanthamoeba keratitis. A study of 70 eyes

BACKGROUND: Acanthamoeba keratitis is an uncommon condition which is usually associated with contact lens wear. The use of home made saline and poor hygiene are important risk factors. Early diagnosis is crucial since these cases respond well to medical therapy. The purpose of this paper is to describe and demonstrate early clinical signs. METHOD: Between September 1992 and October 1994, 70 cases of acanthamoeba keratitis, one of them bilateral, were prospectively monitored at Moorfields Eye Hospital in London. A database of all patients was set up and the clinical findings, diagnostic methods, therapeutic interventions and the outcome were recorded. RESULTS: 66 patients (96%) were contact lens wearers, 64 of them (97%) wore soft lenses. The mean interval between first symptoms and correct diagnosis was 42%. The most frequent initial diagnoses were "unclear keratoconjunctivitis" and "herpetic keratitis". Early corneal findings included punctate keratopathy (n = 14; 20%), pseudodendrites (n = 4; 6%), epithelial infiltrates (n = 17; 24%), diffuse or focal sub-epithelial infiltrates (n = 36; 51%) and radial keratoneuritis (n = 5; 7%). Ring infiltrates (n = 13; 18%) and corneal ulceration (n = 13) were late signs. CONCLUSION: When the above corneal findings are observed, particularly in contact lens wearers, the diagnosis of acanthamoeba keratitis should be considered. The diagnosis of "herpetic keratitis" in association with contact lens wear should be encountered with scepticism.     

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.     

Infiltrative keratitis with contact lens wear--a review

BACKGROUND: "Infiltrates" of white blood cells aggregating in the superficial cornea are common with corneal inflammation. The etiologies of such inflammation vary widely and include an association with contact lens wear. METHODS: This paper reviews the literature regarding corneal infiltrative keratitis with contact lens wear. Basic mechanisms in the development of corneal infiltrates as well as etiologies are presented. Associations and causes, clinical presentation, differential diagnosis, course, and treatment for corneal infiltrates in contact lens wearers are reviewed. CONCLUSIONS: Corneal infiltrates associated with contact lens wear may stem from a variety of causes including factors related to the lens material, design, condition; the lens wearing schedule; environmental factors such as external environment; and lens care patterns, procedures, and products. Individuals who wear contact lenses are also subject to the many non-contact lens-related stimuli to corneal infiltration. Accurate diagnosis and appropriate management of corneal infiltrates with contact lens wear is important, especially due to the possibility of infectious etiology.     

Preventing complications in people who wear contact lenses

The number of contact lens wearers has steadily increased over the past 10 years. Convenience, efficiency and availability of different types of lenses have made them popular. The rise in the use of contact lenses has increased the number of people at risk of contact lens-related complications. Studies have highlighted the consequences of poor contact lens care. Acanthamoeba keratitis is one of the most devastating complications of contact lens wear and can be avoided by adhering to the recommended contact lens regimen. This article reviews the literature on the complications of contact lens wear and stresses the need to educate the wearer. It examines the nurse's role in relation to health promotion and the basic principles for successful long-term contact lens wear. This information is relevant to all nurses caring for people with contact lenses and will be of particular interest to the nurse who wears contact lenses.     

Gonorrhoea in Coventry 1991-1994: epidemiology, coinfection and evaluation of partner notification in the STD clinic

BACKGROUND: Contact lens wearers are subject to increased risk of infection, and an attempt was made to determine which factors cause the overproportional risk of infection? PATIENTS: The aim of this paper is to explain with appropriate bibliographic support why people who wear contact lenses are at risk of infection. RESULTS: The relative risk of keratitis is a function of the lens material and the wearing time of the contact lenses. Extended wear of hydrogel lenses is associated with an overproportional risk of infection. According to the literature, the frequency of complications in contact lens wearers generally is the result of poor hygiene in 66% of the cases. The general lack of hygiene among contact lens wearers must, therefore, be regarded as one cause among pathophysiological mechanisms of the eye. The microbial spectrum favors gram-negative bacteria living in a wet environment such as Pseudomonas, Serratia and parasites like Acanthamoeba. CONCLUSION: The specific spectrum of pathogens and new problem organisms not only challenge the fitter but also the manufacturers to adapt hygiene (sanitary) measures and products to the new development. Disposable contact lens systems are the first step, but they do not solve all the problems of contact lens wearers. Therefore, the importance of contact lens hygiene must be especially emphasized when the ophthalmologist is giving instructions to the patient. On the other hand, hygiene should also not be neglected by the contact lens fitters since it is part of the whole problem.     

Enhanced hepatotoxicity of acetaminophen in the alcoholic patient. Two case reports and a review of the literature

PURPOSE: Bacterial adherence or binding to the target cell is a prerequisite for the initial stage of most infections and seems to be mediated by lectin-like ligands on the bacterial surface and specific receptors on the target cell membrane. The purpose of this study was to establish whether contact lens wear under closed eye conditions changes the glycocalyx layer, whether it exposes more lectin receptors than eye closure without a contact lens, and whether wear of low oxygen transmissibility (Dk/L) contact lenses exposes more receptors than high Dk/L contact lenses. METHODS: The eyes of six rabbits under general anesthesia were fit with either a high Dk/L soft contact lens (40 x 10(-9), boundary corrected) or a low Dk/L soft contact lens (2 x 10[-9]) or were left without a lens as controls. All eyes were kept closed by suturing for 24 hours. After removal of the contact lenses, all corneas were excised, put in glutaraldehydeforfixation, rinsed, incubated with plant-derived lectins (wheat-germ agglutinin [WGA]) conjugated with gold particles, and prepared for electron microscopy. Membrane associated gold particles were counted and the results were processed statistically. RESULTS: After 24 hours of lens wear under closed eye conditions, the glycocalyx layer showed physical changes in the form of thinning or compression and signs of biochemical changes reflected as an increase in number of WGA receptors. The average number of membrane associated gold particles per 750 micro length of corneal epithelium in control corneas was 1,287.5 +/- 92.5. Particles were significantly (P<0.001) more numerous after wear of high Dk/L contact lenses (3,230.0 +/- 294.5) and after wear of low Dk/L contact lenses (4,611.3 +/- 223.3). The figure after wear of low Dk/L contact lenses was significantly (P<0.01) higher than the figure after wear of high Dk/L contact lenses. CONCLUSION: Our results indicate that lens wear under closed eye conditions seems to change the corneal glycocalyx layer physically as well as biochemically. Significantly larger numbers of WGA receptors were exposed after contact lens wear than without a contact lens. Significantly more receptors were exposed after wear of low Dk/L contact lenses than after wear of high Dk/L contact lenses. These changes may be of importance in relation to the risk of bacterial keratitis.     

Prepare to negotiate your next employment agreement

PURPOSE: The purpose of this study was to evaluate the outcome of patients with healed moderate to severe contact lens-associated corneal infectious ulcers who were re-fit with contact lenses. METHODS: We retrospectively studied patients who were fit with contact lenses on our service and who had had moderate to severe corneal infectious ulcers associated with previous contact lens use. Six patients were included in the study. RESULTS: Gas permeable contact lenses were fit in five patients, and a soft contact lens was fit in one patient. Successful fit was achieved in all cases and visual acuities were equal to or better than 20/30 in all patients. No significant complications were observed after a mean follow-up of 23 months (range, 6-45 months). CONCLUSION: In this small series of patients with a history of moderate to severe contact-lens related infectious keratitis, no complications were observed after contact lenses were refit. Contact lens wear in patients with a history of infectious keratitis may be safe and useful in order to achieve visual rehabilitation.     

Amebic keratitis in a wearer of disposable contact lenses due to a mixed Vahlkampfia and Hartmannella infection

PURPOSE: To support the hypothesis that Acanthamoeba is not a unique cause of amebic keratitis, we report a case of amebic keratitis in which viable Acanthamoeba could not be isolated from corneal tissue. Vahlkampfia and Hartmannella, two other genera of free-living ameba, were isolated, however, using prolonged culture. METHODS: A 24-year-old wearer of soft contact lenses had keratitis. Extensive histologic and microbiologic investigations were performed on corneal scrape, biopsy, and keratoplasty tissue. Contact lenses, storage case, and the home water supply, where contact lens hygiene was practiced, were examined for the presence of micro-organisms. RESULTS: No viruses, pathogenic bacteria, or fungi were detected from corneal tissue samples. Amebae were observed using light and electron microscopy, but these could not be unequivocally classified using immunocytochemical staining. Viable Vahlkampfia and Hartmannella, but no Acanthamoeba, were isolated from the corneal biopsy sample. Indirect immunofluorescence with a range of polyclonal rabbit antisera raised against axenically cultivated stains of the three amebal genera was unhelpful because of cross-reactivity. A diverse range of micro-organisms was present within the storage case, including the three amebal species. Amebic cysts also were associated with the contact lens. CONCLUSION: A mixed non-Acanthamoeba amebic keratitis has been identified in a wearer of soft contact lenses where lack of storage case hygiene provided the opportunity for the free-living protozoa Vahlkampfia and Hartmannella to be introduced to the ocular surface. When Acanthamoeba-like keratitis occurs, but where Acanthamoeba cannot be isolated using conventional laboratory culture methods, alternate means should be used to identify other amebae that may be present. Polyclonal immunofluorescent antibody staining was unreliable for generic identification of pathogenic free-living amebae in corneal tissue.     

Decreased corneal sensation as an initial feature of Acanthamoeba keratitis

BACKGROUND: Herpes simplex keratitis is the most common misdiagnosis in patients with Acanthamoeba keratitis, which is increasing in frequency and is associated with daily wear soft contact lenses. Both entities usually present as unilateral keratitis. The manifestations of superficial Acanthamoeba keratitis (i.e., unilaterality, dendriform appearance, positive response to antivirals, and decreased corneal sensation) increase the opportunity for misdiagnosis as herpes simplex keratitis. The authors have encountered six patients with Acanthamoeba keratitis in whom the correct diagnosis was delayed from 2 weeks to 3 months. METHODS: All six patients underwent testing with the Cochet-Bonnet esthesiometer and extensive pharmacologic treatment for herpes simplex keratitis. Corneal scrapings were taken between 2 and 6 weeks after the initial examination. RESULTS: In all six patients, corneal sensation was decreased significantly. Drug therapy was ineffective. Cultures were positive for Acanthamoeba. Five of six patients underwent penetrating keratoplasty. CONCLUSIONS: Decreased corneal sensation has contributed to the misdiagnosis of Acanthamoeba as herpes simplex keratitis. Misdiagnosis results in delayed treatment and worse outcome. The authors found that significantly decreased corneal sensation is a frequent finding in early Acanthamoeba keratitis. Therefore, physicians should consider Acanthamoeba keratitis as an alternative diagnosis in patients with presumed herpes simplex keratitis with decreased corneal sensation.     

Evolution of C4 photosynthesis in response to changes in carbon and oxygen concentrations in the atmosphere through time

This work is a survey of 82 cases of keratoconus which have been followed up for 1 to 12 years. Among them only 66 were fitted with contact lenses. The contra-indications for them are: 1. a better visual acuity with spectacles than with contact lenses, 2. advanced cases (4th degree of Amsler) whose fitting is impossible, 3. unilateral keratoconus, 4. associated diseases such as trachomatous pannus, allergic kerato-conjunctivitis. Hard corneal lenses are now in use in most of the cases. Scleral lenses are much less used than they were 10 years ago, owing probably to the great improvement of the corneal lenses during this time. These hard corneal lenses have a short Ro (4 to 7 mm), an overall diameter between 8 and 11 mm, and an optic diameter of 5 mm. They are fitted under fluorescein control. The mobility must be good too. One case was fitted with soft lenses. The visual acuity is good and so is the tolerance: 80% of the patients wear their lenses 10 hours a day or more. Contact lenses do not affect the progression of keratoconus thus finally a keratoplasty must be performed in many cases. After the operation a contact lens is very often necessary, but its daily wearing time must be divided by two, to avoid corneal neo-vascularisation. Soft corneal lenses may be used in some cases of keratoconus. They are indicated when the hard lenses are no longer tolerated and before a keratoplasty. The base curves of these soft lenses are not related to the radii of the conic cornea. In most of the cases they are between 7.50 and 8.60 mm. The diameter is large: 14 or 15 mm. The lenses must not move too much: 1 mm up or down when the patient blinks. The edge of the lens must not depress the bulbar conjunctiva and there must be no air bubble under the lens. In many cases a cylindrical spectacle lens is necessary to obtain a good visual acuity. Some authors prefer to fit a hard corneal lens over the soft one: this is the "piggy back" method. Sometimes keratoconus has appeared in patients already fitted during several years to correct a myopic astigmatism. It is not clear whether these keratoconus have been produced or not be the contact lenses.     

Effect of the length of wear of contact lenses on corneal sensitivity

Corneal touch thresholds (CTT) were determined once in the morning before inserting contact lenses then after 4, 8 and 12 h of continuous wear. Two groups of subjects participated in this study; 12 persons wearing hard contact lenses and 15 wearing soft contact lenses. All subjects were perfectly adapted to their contact lenses and had worn them for not less than three months. It was found that hard contact lenses caused a progressive diminution of corneal sensitivity. After 12 h corneal sensitivity was, on average, 110% lower (that is an increase of the threshold) than in the morning. Soft lenses also caused a progressive reduction of corneal sensitivity which after 12 h wear was, on average, 45% lower than in the morning, although there were marked differences. Moreover, 9 of the hard contact lens subjects had been tested a year earlier and it was found that their CTT after 8 h wear had slightly but not significantly diminished which indicated that these subjects had not adapted significantly to their lenses in one year.     

Effect of topical anesthetic use on initial patient satisfaction and overall success with rigid gas permeable contact lenses

BACKGROUND: Rigid gas permeable (RGP) contact lenses have numerous benefits; however, RGP lens use is not increasing in the United States. An important factor for this trend has been initial comfort. Studies have demonstrated that how RGPs are presented to patients, in addition to lens design, can play an important role in the initial comfort process. Another important factor could be the use of a topical anesthetic during the fitting and dispensing visits. The purpose of this study was to use a multicenter format to determine if topical anesthetic use increased the likelihood of patient satisfaction and success. METHODS: A total of 80 subjects, with no previous rigid lens wear experience, was entered into this 1-month study, including 20 subjects from each of 4 institutions. Subjects were randomly divided into the following two groups: (A) anesthetic or (B) placebo, with the former group receiving one drop of a topical anesthetic before lens insertion at both the diagnostic fitting and dispensing visits, whereas the latter group received a placebo. Subjects completed a questionnaire on their perception of rigid lens wear both immediately before fitting and at the 1-month visit. After diagnostic fitting with rigid lenses, subjects completed an adaptation questionnaire after 15 min, 1 week, 2 weeks, and 1 month of lens wear. RESULTS: Seventy of the 80 subjects completed the study and, of the 10 subjects who discontinued, 8 were in the placebo group. In all categories evaluated, the anesthetic group experienced a more optimum adaptation experience at each visit vs. the placebo group. Specifically, overall comfort was rated significantly higher at both dispensing and 2 weeks. In addition, the anesthetic group exhibited significantly greater overall satisfaction with rigid lens wear at 2 and 4 weeks. Also, the anesthetic group perceived their adaptation, sensitivity, and adaptation time to be significantly better at the 1-month visit. There was no significant difference in corneal staining between these two groups at each visit, with the exception of a greater amount of staining in the central quadrant for the placebo group at the 1-month visit. CONCLUSIONS: The use of a topical anesthetic at the fitting and dispensing visits for first-time wearers of RGP lenses resulted in significantly fewer dropouts, improved initial comfort, an enhanced perception of the adaptation process, and greater overall satisfaction after 1 month of lens wear as compared to the use of a nonanesthetizing placebo at those visits. This result, in combination with both presenting RGP lenses in a nonthreatening manner and optimizing the lens design and fitting relationship, should result in a positive adaptation process and successful wear of RGP contact lenses.     

Effect of proteolysis on the state of lipid phase in rat brain synaptosomal membranes

Polymethylmethacrylate (PMMA) contact lenses can alter corneal shape and induce corneal warpage or distortion. The purpose of our study was to determine the effects on the corneal topography after immediate refitting of long-term PMMA contact lens wearers into rigid gas permeable (RGP) materials. Six eyes with contact lens induced corneal warpage from PMMA contact lenses were assessed using the Topographical Mapping System-1. Statistical analysis was performed for the following variables prior to and approximately 6 months after contact lens refitting: best spectacle visual acuity, manifest refraction, surface regularity index, surface asymmetry index, keratometry, and simulated keratometry. Best spectacle visual acuity improved an average of 1.8 +/- 1.0 (mean +/- SD, P < 0.05) lines of Snellen visual acuity, while refraction did not change appreciably. The surface regularity index diminished by 0.51 +/- 0.32 (P = 0.01). The surface asymmetry index improved by 0.32 +/- 0.26 (P < 0.05). There was a good correlation between keratometry and simulated keratometry, and neither changed significantly after refitting with RGP contact lenses. All general topographic patterns remained unchanged throughout the study. Immediate refitting of long-term PMMA contact lens wearers into RGP materials of similar fit allows a slightly more regular and symmetric central corneal shape, which can result in improved spectacle visual acuity. The general corneal topographic patterns of contact lens induced corneal warpage did not change or improve after refitting to RGP material.     

Congenital perilymphatic fistula and associated middle ear abnormalities

An analysis of central microbial keratitis with respect to etiology, recovery, complications and visual outcome was carried out in Gothenburg, Sweden, during a 3-year period. Gram positive bacteria were found in 22 out of 48 cases; Staphylococcus aureus and Staphylococcus epidermidis accounted for more than 50% of these Gram positive cases. Pseudomonas was the most common Gram negative bacterium. No case with etiology of fungus was found. The contact lens wearers showed mainly the same bacterial spectrum as non-wearers. The initial 'shotgun' therapy with cefuroxime and gentamycin seemed adequate for this bacterial spectrum. Seventy percent of the eyes healed within 3 weeks. Contact lens wear and trauma were found to be the two major predisposing factors in the cases with microbial keratitis. The lens wearers had shorter recovery times than the non wearers. The visual results after one month were good in 50% of the eyes, and another 12% attained useful vision.     

Etiology of corneal striae accompanying hydrogel lens wear

Vertical striae in the posterior cornea were produced experimentally in ten human subjects by depriving the anterior corneal surface of its normal oxygen supply and inducing corneal edema. These striae were similar in appearance and time of occurrence to those observed in gel lens wearers. Three subjects also wore gel lenses and developed vertical striae while wearing their lenses. These striae were eliminated by increasing the oxygen concentration at the anterior lens surface. The data confirm many clinical observations which have suggested that verical striae are caused by corneal edema accompanying gel lens wear.     

MR detection of hyperacute parenchymal hemorrhage of the brain

OBJECTIVE: This study aimed to assess the effect of contact lens wear on the mucosal defenses of the outer eye against infection. DESIGN: A case-controlled study of daily contact lens wearers in their initial 6 months of contact lens wear. PARTICIPANTS: Contact lens wearers (mean age, 23.1 years; 47 subjects) were compared with age-matched control subjects (mean age, 24.7 years; 44 subjects). INTERVENTION: Outer eye defenses were studied by assay of tear constituents and quantitative conjunctival microbiology. MAIN OUTCOME MEASURES: Antimicrobial activity of tears was studied by assay of total immunoglobulin A (IgA), IgA isotype-specific antibodies reactive with Escherichia coli, Haemophilus influenzae, Staphylococcus epidermidis, albumin and lysozyme, and the ocular surface microbial load determined using quantitative microbiology of the conjunctival sac. RESULTS: The IgA isotype-specific antibodies reactive with E. coli (P = 0.03) and S. epidermidis (P = 0.068) were lower in contact lens wearers, but antibody:albumin ratios were not significantly different in the two groups. Contact lens wear also had no significant effect on tear IgA, albumin, or lysozyme or its ratios with albumin. Bacterial numbers and colonization rates for coagulase-negative staphylococci were greater in contact lens wearers than in age-matched control subjects. Corynebacterium sp. and non-Enterobacteriaceae (P = 0.007) were isolated more frequently and in greater numbers from contact lens wearers. Colonization rates were increased for Corynebacterium sp., but non-Enterobacteriaceae were transient. In both daily contact lens wearers and age-matched control subjects, most conjunctival flora were transient rather than colonizing, and no subject developed an outer eye infection during the study. CONCLUSION: These results suggest that daily contact lens wear does not significantly alter the mucosal defenses of the outer eye that function to eliminate organisms from the conjunctival sac and prevent outer eye infection.     

Ophthalmology

It is estimated that 49% to 74% of cases of contact lens-associated ulcerative keratitis could be prevented by eliminating overnight wear. Heavy alcohol consumption appears to be associated with all types of cataracts. Cigarette smokers have a nearly threefold greater risk of developing age-related macular degeneration than nonsmokers.     

Extended wear silicone contact lenses in children with cataracts

Thirty-twop patients, ranging in age from three weeks to 22 years, were fitted with an extended wear 100% silicone lens. The longest period of time a lens remained in the eye without being removed was 120 days. Most lenses were worn an average of six weeks before cleaning was required. No cases of infection or corneal edema were observed that required discontinuing use of the lens.