Microbial keratitis and vision loss with contact lenses

Silicone hydrogel versus hydrogel soft contact lenses for differences in patient-reported eye comfort and safety

BACKGROUND

Ocular discomfort is the leading cause of permanent discontinuation of soft contact lens (SCL) wear. Silicone hydrogel and hydrogel materials are the two major categories of SCLs, with silicone hydrogel materials being newer and more breathable than hydrogel materials. Whether comfort is associated with SCL material is controversial despite numerous studies. Similarly, the difference between these materials in terms of safety outcomes (e.g. frequency of microbial keratitis) is unclear.

OBJECTIVES

To evaluate the comparative effectiveness and safety of silicone hydrogel compared with hydrogel SCLs on self-reported comfort, dry eye test results, and adverse events in SCL-wearing adults 18 years of age or older.

SEARCH METHODS

The Cochrane Eyes and Vision Information Specialist searched the electronic databases for randomized controlled trials (RCTs). There were no restrictions on language or date of publication. We searched the Cochrane Central Register of Controlled Trials (CENTRAL, including the Cochrane Eyes and Vision Trials Register; 2022, Issue 6), MEDLINE Ovid, Embase.com, PubMed, LILACS (Latin American and Caribbean Health Science Information database), ClinicalTrials.gov, and World Health Organization (WHO) International Clinical Trials Registry Platform (ICTRP). We also searched the reference lists of identified studies, review articles, and guidelines for information about relevant studies that may not have been identified by our search strategy. Furthermore, we contacted investigators regarding ongoing trials. The most recent database search was conducted on 24 June 2022.

SELECTION CRITERIA

Our search selection criteria included RCTs, quasi-RCTs, and cross-over RCTs.

DATA COLLECTION AND ANALYSIS

We applied standard Cochrane methodology.

MAIN RESULTS

We included seven parallel-group RCTs conducted in the USA, the UK, Australia, Germany, India, and Turkey. A total of 1371 participants were randomized. The duration of SCL wear ranged from one to 52 weeks. Study characteristics and risk of bias The median number of participants per trial was 120 (interquartile range: 51 to 314), and the average age ranged from 20.7 to 33.0 years. Women represented the majority of participants (range 55% to 74.9%; 5 RCTs). Collectively, the included trials compared eight different silicone hydrogel SCLs with three different hydrogel SCLs. Five trials compared daily disposable SCLs, and two compared extended wear SCLs (worn for seven days and six nights). New SCL wearers were enrolled in three trials. Two trials included both new and established SCL wearers, and two trials did not report participants' history of SCL use. Five trials were sponsored by industry. We judged the overall risk of bias to be 'high' or 'some concerns' for the safety and efficacy outcomes. Findings One trial reported Ocular Surface Disease Index (OSDI) results, with the evidence being very uncertain about the effects of SCL material on OSDI scores (mean difference -1.20, 95% confidence interval [CI] -10.49 to 8.09; 1 RCT, 47 participants; very low certainty evidence). Three trials reported visual analog scale comfort score results, with no clear difference in comfort between materials, but the evidence was of very low certainty; trial results could not be combined because the three trials reported results at different time points. The evidence is very uncertain about the effect of SCL material on discontinuation of contact lens wear (risk ratio [RR] 0.64, 95% CI 0.11 to 3.74; 1 RCT, 248 participants). None of the included trials reported Contact Lens Dry Eye Questionnaire (CLDEQ-8) or Standard Patient Evaluation of Eye Dryness (SPEED) scores. There was no evidence of a clinically meaningful difference (> 0.5 unit) between daily disposable silicone hydrogel and hydrogel SCLs in corneal staining, conjunctival staining, or conjunctival redness (very low certainty evidence). Adverse events Very low certainty evidence from two trials comparing daily disposable SCLs suggested no evidence of a difference between lens materials in the risk of vision-threatening adverse events at one to four weeks (RR 0.68, 95% CI 0.08 to 5.51; 2 RCTs, 368 participants). Two trials comparing extended wear SCLs indicated that hydrogel SCLs may have a 2.03 times lower risk of adverse events at 52 weeks compared with silicone hydrogel SCLs (RR 2.03, 95% CI 1.38 to 2.99; 815 participants), but the certainty of evidence was very low.

AUTHORS' CONCLUSIONS

The overall evidence for a difference between all included silicone hydrogel and hydrogel SCLs was of very low certainty, with most trials at high overall risk of bias. The majority of studies did not assess comfort using a validated instrument. There was insufficient evidence to support recommending one SCL material over the other. For extended wear, hydrogel SCL may have a lower risk of adverse events at 52 weeks compared to silicon hydrogel. Future well-designed trials are needed to generate high certainty evidence to further clarify differences in SCL material comfort and safety.

CLEAR - Medical use of contact lenses

The medical use of contact lenses is a solution for many complex ocular conditions, including high refractive error, irregular astigmatism, primary and secondary corneal ectasia, disfiguring disease, and ocular surface disease. The development of highly oxygen permeable soft and rigid materials has extended the suitability of contact lenses for such applications. There is consistent evidence that bandage soft contact lenses, particularly silicone hydrogel lenses, improve epithelial healing and reduce pain in persistent epithelial defects, after trauma or surgery, and in corneal dystrophies. Drug delivery applications of contact lens hold promise for improving topical therapy. Modern scleral lens practice has achieved great success for both visual rehabilitation and therapeutic applications, including those requiring retention of a tear reservoir or protection from an adverse environment. This report offers a practical and relevant summary of the current evidence for the medical use of contact lenses for all eye care professionals including optometrists, ophthalmologists, opticians, and orthoptists. Topics covered include indications for use in both acute and chronic conditions, lens selection, patient selection, wear and care regimens, and recommended aftercare schedules. Prevention, presentation, and management of complications of medical use are reviewed.

Risk Factors for Contact Lens-Related Microbial Keratitis and Associated Vision Loss in a South Indian Population

OBJECTIVES

To identify risk factors associated with contact lens-related microbial keratitis (CL-MK) and subsequent vision loss in a south Indian population.

METHODS

A retrospective study of medical records at the LV Prasad Eye Institute in Hyderabad, India, of patients diagnosed with CL-MK and of controls who had no history of corneal inflammation during contact lens wear was undertaken. Variables such as demographic data, contact lens wear details, duration of the event, visual acuity, epithelial defect and infiltrate size, and microbiology of the cornea during the event were collected. Differences between cases and controls were analyzed using parametric and nonparametric tests. Logistic regression was used to calculate the odds ratio (OR) and associated 95% confidence intervals in univariate and multivariate analyses for cases vs. controls and for factors associated with vision loss.

RESULTS

One hundred sixty-seven cases of CL-MK and 153 controls were included in the analyses. Risk factors associated with the greatest increased OR for CL-related MK were: being in professional employment vs. a student (OR=3.9), disposing lenses yearly versus monthly or biweekly (OR=2.2), and any overnight wear (OR=2.8). Risk factors associated with vision loss were: high myopia (OR=3.6), severe vs. mild severity (OR=16.0), and hypopyon (OR=4.3).

CONCLUSIONS

Identification of these risk factors may help inform safe contact lens wear habits and management strategies.

Antimicrobial efficacy of a novel povidone iodine contact lens disinfection system

PURPOSE

Contact lens (CL) wear is a risk factor for the acquisition of microbial keratitis. Accordingly, compliance to manufacturers' recommended hygiene and disinfection procedures are vital to safe (CL) use. In this study we evaluated a novel povidone-iodine (PI) (CL) disinfection system (cleadew, Ophtecs Corporation, Japan) against a range of bacterial, fungal and Acanthamoeba.

METHODS

Antimicrobial assays were conducted according to ISO 14729 using the recommended strains of bacteria and fungi, with and without the presence of organic soil. Regrowth of bacteria and fungi in the disinfection system was also examined. The activity on biofilms formed from Stenotrophomonas maltophilia and Achromobacter sp. was evaluated. Efficacy against A. castellanii trophozoites and cysts was also investigated.

RESULTS

The PI system gave >4 log₁₀ kill of all bacteria and fungi following the manufacturer's recommended disinfection and cleaning time of 4h, with or without the presence of organic soil. No regrowth of organisms was found after 14days in the neutralized solution. In the biofilm studies the system resulted in at least a 7 log₁₀ reduction in viability of bacteria. For Acanthamoeba, >3 log₁₀ kill of trophozoites and 1.1-2.8 log₁₀ kill for the cyst stage was obtained.

CONCLUSIONS

The PI system effective against a variety of pathogenic microorganisms under a range of test conditions. Strict compliance to recommended CL hygiene procedures is essential for safe CL wear. The use of care systems such as PI, with broad spectrum antimicrobial activity, may aid in the prevention of potentially sight threatening microbial keratitis.

The comparison of antimicrobial effectiveness of contact lens solutions

PURPOSE

The aim of this study was to compare the effects of widely used multipurpose contact lens solutions against Staphylococcus aureus and Pseudomonas aeruginosa, in addition to cystic and trophozoite forms of Acanthamoeba castellanii and A. polyphaga, that cause microbial keratitis.

METHODS

Three multipurpose solutions were tested: SOLO-care, ReNu, and Opti-Free Express. The test solutions were challenged with P. aeruginosa (ATCC 27853) and S. aureus (ATCC 2913) based on the ISO stand-alone and regiment test procedure for disinfecting products, A. polyphaga (ATCC 30871) and A. castellanii (1501/1A) cystic and trophozoite forms. Multipurpose solutions were sampled for surviving microorganisms at manufacturer's minimum recommended disinfection time. The number of viable organisms was determined, and log reductions were calculated.

RESULTS

ReNu and SOLO-care resulted in a reduction greater than the required mean 3.0 logarithmic reduction against S. aureus, and SOLO-care and Opti-Free Express resulted in a reduction more than the required mean 3.0 logarithmic reduction against P. aeruginosa. Against the cystic and trophozoite forms of A. castellanii, the log reduction provided by SOLO-care was 1.01 and 1.31 log, respectively. ReNu provided a 0.83 log reduction of the cystic form and a 1.21 log reduction of the trophozoite form. Using Opti-Free Express, the log reduction for both forms was 1.31. SOLO-care led to a 0.61 log reduction of the cystic form of A. polyphaga and a 1.01 log reduction of the trophozoite form. ReNu provided a 0.41 log reduction of the cystic form and a 4.99 log reduction of the trophozoite form. Opti-free Express resulted in a 0.89 log reduction of the cystic form and a 3.11 log reduction of the trophozoite form.

CONCLUSIONS

Multipurpose contact lens solutions using similar regimens can show different disinfection abilities.

Modulation of immune signaling, bacterial clearance, and corneal integrity by toll-like receptors during streptococcus pneumoniae keratitis

PURPOSE

Bacterial keratitis, without effective antimicrobial treatment, leads to poor patient prognosis. Even after bacterial clearance, the host inflammatory response can contribute to corneal damage. Though Streptococcus pneumoniae (pneumococcus) is a common cause of bacterial keratitis, the role of host innate immunity during pneumococcal keratitis is not well characterized. This study investigated the role of Toll-like receptors (TLRs) during pneumococcal keratitis.

MATERIALS AND METHODS

C57BL/6, as well as TLR2(-/-) and TLR4(-/-) mice, were infected with S. pneumoniae, and infected corneas were examined for 21 days. Quantitative real-time reverse-transcriptase polymerase chain reaction was performed using primers for genes involved in the inflammatory response and TLR signaling. Bacterial survival and leukocyte invasion were examined over a 72-h period.

RESULTS

The corneal expression of TLR2, TLR4, and other inflammatory genes was increased at 72 h post-infection (p.i.) compared to uninfected C57BL/6 scratch controls. TLR2(-/-) mice showed a significant increase in bacterial survival at 24 h p.i. likely due to decreased neutrophil infiltration; however, after Day 5 p.i. observed clinical scores of TLR2(-/-) and C57BL/6 mice were not significantly different. In contrast, permanent corneal damage was observed for TLR4(-/-) mice over 21 days. Initially, both TLR(-/-) mouse strains exhibited lower expression levels in many immune genes, but returned to similar or elevated levels compared to C57BL/6 mice by 72 h p.i.

CONCLUSIONS

TLR2 and TLR4 are involved in the response to pneumococcal keratitis and TLR2 may aid in bacterial clearance by recruitment of neutrophils to the cornea, whereas TLR4 may be necessary to modulate the immune response to limit cellular damage.

Active Immunization with Pneumolysin versus 23-Valent Polysaccharide Vaccine for Streptococcus pneumoniae Keratitis

PURPOSE

The purpose of this study was to determine whether active immunization against pneumolysin (PLY), or polysaccharide capsule, protects against the corneal damage associated with Streptococcus pneumoniae keratitis.

METHODS

New Zealand White rabbits were actively immunized with Freund's adjuvant mixed with pneumolysin toxoid (ψPLY), Pneumovax 23 (PPSV23; Merck, Whitehouse Station, NJ), or phosphate-buffered saline (PBS), before corneal infection with 10⁵ colony-forming units (CFU) of S. pneumoniae. Serotype-specific rabbit polyclonal antisera or mock antisera were passively administered to rabbits before either intravenous infection with 10¹¹ CFU S. pneumoniae or corneal infection with 10⁵ CFU of S. pneumoniae.

RESULTS

After active immunization, clinical scores of corneas of the rabbits immunized with ψPLY and Freund's adjuvant were significantly lower than scores of the rabbits that were mock immunized with PBS and Freund's adjuvant or with PPSV23 and Freund's adjuvant at 48 hours after infection (P ≤ 0.0010), whereas rabbits immunized with PPSV23 and Freund's adjuvant failed to show differences in clinical scores compared with those in mock-immunized rabbits (P = 1.00) at 24 and 48 hours after infection. Antisera from rabbits actively immunized with PPSV23 and Freund's adjuvant were nonopsonizing. Bacterial loads recovered from infected corneas were higher for the ψPLY- and PPSV23-immunized rabbits after infection with WU2, when compared with the mock-immunized rabbits (P ≤ 0.007). Conversely, after infection with K1443, the ψPLY-immunized rabbits had lower bacterial loads than the control rabbits (P = 0.0008). Quantitation of IgG, IgA, and IgM in the sera of ψPLY-immunized rabbits showed high concentrations of PLY-specific IgG. Furthermore, anti-PLY IgG purified from ψPLY-immunized rabbits neutralized the cytolytic effects of PLY on human corneal epithelial cells. Passive administration of serotype-specific antisera capable of opsonizing and killing S. pneumoniae protected against pneumococcal bacteremia (P ≤ 0.05), but not against keratitis (P ≥ 0.476).

CONCLUSIONS

Active immunization with pneumococcal capsular polysaccharide and Freund's adjuvant fails to produce opsonizing antibodies, and passive administration of serotype specific opsonizing antibodies offers no protection against pneumococcal keratitis in the rabbit, whereas active immunization with the conserved protein virulence factor PLY and Freund's adjuvant is able to reduce corneal inflammation associated with pneumococcal keratitis, but has variable effects on bacterial loads in the cornea.

Contact lens disinfecting solutions antibacterial efficacy: comparison between clinical isolates and the standard ISO ATCC strains of Pseudomonas aeruginosa and Staphylococcus aureus

PURPOSE

To evaluate the disinfectant properties of the three multipurpose contact lens disinfecting solutions available in Iran, against clinical isolates and the standard ISO ATCC strains of Pseudomonas aeruginosa and Staphylococcus aureus, based on the international organization for standardization (ISO) 14729 guidelines.

METHODS

Three multipurpose solutions that were tested were ReNu Multiplus, Solo Care Aqua and All-Clean Soft. The test solutions were challenged with clinical isolates and the standard strains of P. aeruginosa(ATCC 9027) and S. aureus(ATCC 6538), based on the ISO Stand-alone procedure for disinfecting products. Solutions were sampled for surviving microorganisms at manufacturer's minimum recommended disinfection time. The number of viable organisms was determined and log reductions calculated.

RESULTS

All of the three test solutions in this study provided a reduction greater than the required mean 3.0 logarithmic reduction against the recommended standard ATCC strains of P. aeruginosa and S. aureus. Antibacterial effectiveness of Solo Care Aqua and All-Clean Soft against clinical isolates of P. aeruginosa and S. aureus were acceptable based on ISO 14729 Stand-alone test. ReNu MultiPlus showed a minimum acceptable efficacy against the clinical isolate of S. aureus, but did not reduce the clinical isolate by the same amount.

CONCLUSIONS

Although the contact lens disinfecting solutions meet/exceed the ISO 14729 Stand-alone primary acceptance criteria for standard strains of P. aeruginosa and S. aureus, their efficacy may be insufficient against clinical isolates of these organisms.

Pathogenesis of A Clinical Ocular Strain of Streptococcus pneumoniae and the Interaction of Pneumolysin with Corneal Cells

Streptococcus pneumoniae is an important cause of bacterial keratitis, an infectious disease of the cornea. This study aimed to determine the importance of pneumolysin (PLY), a pneumococcal virulence factor, in keratitis using a clinical keratitis isolate (K1263) and its isogenic mutant deficient in PLY (K1263ΔPLY) and determine the effect of these strains on primary rabbit corneal epithelial (RCE) cells. Each strain was injected into the corneal stromas of rabbits, clinical examinations were performed, and the recovered bacterial loads were determined. Bacterial extracts were exposed to RCE cells, and morphology and viability were assessed. The mutant strain deficient in PLY, K1263ΔPLY, caused significantly lower ocular disease scores than the parent strain (K1263), although a higher bacterial load was recovered from corneas infected with the mutant strain. Histological examination showed increased inflammatory cells in the anterior chamber and increased edema in eyes infected with the parent strain. RCE cells exposed to the parent strain had significantly decreased cell viability and showed increased evidence of cellular damage. This study confirms that in a strain that can cause clinical keratitis, PLY is a significant cause of the damage associated with pneumococcal keratitis. It also shows for the first time that the results from an in vitro model using RCE cells correlates with in vivo results thereby establishing a less invasive way to study the mechanisms of pneumococcal keratitis.

Assessment of Streptococcus pneumoniae capsule in conjunctivitis and keratitis in vivo neuraminidase activity increases in nonencapsulated pneumococci following conjunctival infection

PURPOSE

The pneumococcal capsule is required for pathogenesis in systemic infections, yet reports show most conjunctivitis outbreaks are caused by nonencapsulated pneumococci, while keratitis infections are caused by encapsulated strains. This study aims to determine the effect of capsule in pneumococcal keratitis and conjunctivitis in rabbit models of infection.

METHODS

A capsule-deficient isogenic mutant was created using homologous transformation. Parent and mutant strains were injected within the upper bulbar conjunctiva (conjunctivitis) or into the corneal stroma (keratitis) of New Zealand white rabbits. Clinical examinations were performed 24 and 48 hr post-infection at which time corneas or conjunctivae were removed, homogenized, and plated to determine the recovered bacterial load. Whole eyes were removed for histological examination. The neuraminidase activity was determined following in vitro and in vivo growth.

RESULTS

There were no significant differences in clinical scores between the eyes infected with the parent or mutant for either infection, nor was there a difference in the amount of bacteria recovered from the cornea. In the conjunctivae, however, the mutant strain was cleared by the host faster than the parent strain. Histological examination showed slightly more infiltrating polymorphonuclear leukocytes (PMN) and macrophages in the conjunctivae infected with the parent strain. The neuraminidase activity of both strains was not significantly different when the strains were grown in vitro. However, the neuraminidase activity of the parent was significantly less than that of the mutant at 3 and 12 hr post conjunctival infection.

CONCLUSIONS

Although more outbreaks of pneumococcal conjunctivitis are tied to nonencapsulated S. pneumoniae strains, this study showed that an encapsulated strain was capable of establishing conjunctivitis in a rabbit injection model and survive attack by the host immune system longer than its nonencapsulated isogenic mutant. Nonetheless, the nonencapsulated pneumococci had an increased neuraminidase activity level in vivo when compared to the parent strain.

Corneal thinning associated with recurrent microbial keratitis resulting from 7-day extended wear of low Dk hydrogel contact lenses: a case report

CASE DESCRIPTION

Corneal thinning and an increased risk of corneal perforation, resulting from recurrent episodes of microbial keratitis, required a 38-year-old Caucasian female to undergo bilateral corneal grafting. Although strongly advised otherwise, the patient had been a long time user of low oxygen permeability hydrogel contact lenses in a flexible wear regime, with frequent overnight use.

DISCUSSION

Microbial keratitis is a potentially severe contact lens related complication which, if not properly treated, may lead to permanent visual loss. The introduction of silicone-hydrogel materials and daily replacement modalities has not resulted in a significant decrease in the incidence of microbial keratitis, thus suggesting that the condition is mainly dependent on patient hygiene and wearing habits. Non-compliance, which is endemic in contact lens wear, may be combated by increasing patient awareness of the potential risk factors of contact lens misuse. This is accomplished through constant, rigorous information provided by contact lens practitioners.

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.

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.

Use of silicone hydrogel material for daily wear

Silicone hydrogel contact lenses were initially developed to optimise oxygen transmissibility for extended wear use. The concerns with such contact lenses have been their higher elastomeric and hydrophobic characteristics associated with the incorporation of silicone type monomers. The use of silicone hydrogel has most recently been suggested for daily wear to eliminate all hypoxic related problems. The primary aim of the investigation was to test in vivo wetting performance and subjective acceptance of the first silicone hydrogel contact lens developed for daily wear, ACUVUE ADVANCE with HYDRACLEAR (galyfilcon A), compared to a conventional hydrogel contact lens for the same application SofLens 66 (alphafilcon A). The investigation was a randomised, subject masked bilateral cross over investigation testing of the two contact lens materials over their approved replacement periods (galyfilcon A 2 weeks and alphafilcon A 2 weeks (USA) and 4 weeks (Europe)). In all cases ReNu Multiplus lens care system was used. The investigation carried out on 24 contact lens wearers showed that: (i) in vivo wettability was superior for galyfilcon A which had a thicker lipid layer (thin layer incidence: galyfilcon A 54%; alphafilcon A 70-86%, p<0.05), a thicker aqueous layer (thick layer incidence: galyfilcon A 88%; alphafilcon A 35-64%, p<0.05) and a more stable tear film (galyfilcon A 7.8s; alphafilcon A 2 weeks 5.6s, p=0.022; 4 weeks 7.4s, p=0.276); (ii) for the intended replacement period, comfort was better with galyfilcon A (2 weeks) compared to alphafilcon A (4 weeks) at insertion (p=0.001) and, throughout the day (daytime and evening p=0.008). Contact lenses made from galyfilcon A and replaced two weekly achieved better in vivo wettability than contact lenses made from alphafilcon A and replaced either two and four weekly; the better wettability was associated with an overall better comfort for galyfilcon A.

Rethinking contact lens associated keratitis

This review presents a critical analysis of the literature relating to the use of binomial and polynomial classification schemes for categorising corneal infiltrative events (CIEs) associated with contact lens wear and the epidemiology of such events. The results of the Manchester Keratitis Study-a 12-month, prospective, hospital-based epidemiological study of contact lens wearer suffering from CIEs-are used as a tool to challenge and test traditional thinking in relation to contact lens associated keratitis. An innovative aspect of this study is the use of a novel clinical severity matrix to systematically score the severity of CIEs based on 10 key signs and symptoms. The ambiguities inherent in using binomial classification schemes (such as, microbial versus sterile, ulcerative versus non-ulcerative etcetera) are highlighted. The failure of a polynomial scheme-due to extensive classification overlap between proposed sub-types of CIEs-is demonstrated using a Venn diagram. A cartographic analysis reveals that infiltrates tend to occur in the superior cornea of patients wearing extended wear silicone hydrogel lenses, in the central cornea of patients wearing daily wear hydrogel daily disposable lenses and in the peripheral cornea of patients wearing daily wear hydrogel (excluding daily disposable) lenses. Infiltrates that occur more towards the limbus are less severe. The incidence of CIEs is higher when contact lenses are worn overnight. Logistic analysis reveals that the risk of developing a severe CIE is five times greater with conventional hydrogel extended wear versus silicone hydrogel extended wear. The male gender, smoking, a healthy eye and body, and the late Winter months are associated with an increased risk of developing CIEs. The rate of significant visual loss as a result of developing a CIE is low. Two key conclusions are drawn from this work, which represent a radical rethinking of this potentially sight-threatening condition. CIEs should be considered as a continuous spectrum of ocular disease. If a contact lens wearer presents with a sore eye that is becoming progressively worse and a CIE is observed in that eye, lens wear should be suspended and anti-microbial therapy initiated immediately.

Staphylococcus aureus Ulcer Associated With Continuous Wear of Silicone Hydrogel Contact Lenses

PURPOSE

To report a case of culture-positive Staphylococcus aureus keratitis associated with continuous wear of lotrafilcon A lenses.

METHODS

The case report of a patient who developed microbial keratitis while wearing lotrafilcon A contact lenses is presented.

RESULTS

A 41-year-old white man had worn polymacon contact lenses successfully for at least 10 years. He habitually replaced the lenses every 1 to 2 years and frequently wore them continuously for up to 3 months. He was refitted with silicone hydrogel lenses and was advised to remove and replace the lenses monthly. Approximately 18 months later, he developed a midperipheral, culture-positive S. aureus ulcer in his right eye. He was treated with fortified cefazolin and gentamicin for 2 weeks, followed by ciprofloxacin for 2 weeks. The ulcer resolved completely. The patient's final visual acuity was 20/20 in the affected eye.

CONCLUSIONS

The increased oxygen permeability of silicone hydrogel contact lens materials may reduce the risk of hypoxic complications of continuous contact lens wear. As this case shows, however, even patients who have continuously worn lenses with very low oxygen permeability without incident can develop microbial keratitis when wearing silicone hydrogel lenses. Contact lens practitioners should inform patients of the potential risks of continuous wear and of factors that may increase those risks.

Prolonging contact lens wear and making contact lens wear safer

PURPOSE

To summarize the present status of safety and efficacy of contact lens wear.

DESIGN

Literature review.

METHODS

Ovid Medline searches were performed on records from 1966 through 2005 using keywords: keratitis, contact lens complications, extended-wear contact lenses, and silicone-hydrogel contact lenses.

RESULTS

Patients desire comfort, clarity of vision, and prolonged contact lens wear when contact lenses are used to correct refractive error. Practitioners desire patient satisfaction but also require maintenance of the integrity of the eye and no complications that jeopardize vision or health of the eye. Improvements in the oxygen permeability of the contact lens materials, design of the contact lens and its surface, and solutions for the maintenance of the lens have reduced but not eliminated the risks of infection, inflammation, and conjunctival papillary reaction associated with contact lens wear. The lessons of past and recent history suggest that patient education and practitioner participation in the management of contact lens wear continue to be critical factors for patient satisfaction and safety in the extended wear of contact lenses.

CONCLUSIONS

The availability of highly oxygen permeable contact lenses has increased the tolerance and safety of extended contact lens wear, but patient instruction and education in proper use and care of lenses is required and caution is advised.

Incidence and morbidity of hospital-presenting corneal infiltrative events associated with contact lens wear

AIM

To determine the incidence and morbidity (visual loss) of hospital-presenting corneal infiltrative events (CIEs) associated with the wearing of current generation contact lenses.

METHODS

All contact lens wearers presenting with any form of corneal infiltrate/ulcer to a hospital centre in Manchester, UK, were surveyed in this 12-month, prospective, hospital-based epidemiological study. A clinical severity matrix was used to quantify the overall severity of presenting signs and symptoms. The size of the hospital catchment population and the wearing modalities (daily wear [DW] or extended wear [EW]) and lens types used in that population were estimated from relevant demographic and market data to facilitate the calculation of incidence. We also attempted to ascertain, from their eye care practitioners, the visual acuity (VA) of patients suffering from CIEs prior to and at about six months following attendance at the hospital.

RESULTS

During the survey period, 118 patients presented with CIEs of varying severity. The annual incidence (cases per 10,000 wearers) for all wearing modalities and lens types is 21.3 (95 per cent confidence interval 17.8 to 25.5). The incidence of CIEs for each wearing modality and lens type is: DW rigid, 8.6 (3.9 to 18.7); DW hydrogel daily disposable, 14.0 (9.3 to 21.0); DW hydrogel (excluding daily disposable), 20.4 (15.9 to 26.2); DW silicone hydrogel, 55.9 (9.9 to 309.6); EW rigid, zero (0.0 to 1758.8); EW hydrogel, 144.6 (66.4 to 311.8) and EW silicone hydrogel, 118.6 (75.2 to 186.7). The risk of developing a CIE with EW lenses was 8.1 (5.3 to 12.5) times greater than that with DW lenses (p < 0.0001). Although there was no difference between EW hydrogel and EW silicone hydrogel lenses with respect to the risk of developing CIEs, the clinical severity of CIEs was greater with EW hydrogel lenses (p = 0.04). Results of VA for pre- and post-hospital attendance were obtained from 38 patients, none of whom lost more than one line of VA. For the study population, zero patients (95 per cent CI: 0 to 9.2 per cent) suffered a significant loss of VA as a result of developing a CIE.

CONCLUSIONS

Overall, there is an eight times higher incidence of CIEs in wearers who sleep in contact lenses compared with wearers who use lenses only during the waking hours. For those who choose to routinely or intermittently sleep in soft contact lenses, silicone hydrogels are the lens of first choice because CIEs are less clinically severe with this lens type compared with hydrogel lenses. The rate of significant visual loss as a result of developing a CIE is low.

Pseudomonas aeruginosa Keratitis in an Atopic Silicone Hydrogel Lens Wearer With Rosacea

PURPOSE

This case report documents Pseudomonas aeruginosa corneal infection associated with daily wear of a silicone contact lens in a patient who also had bilateral, preexisting biomicroscopic findings of ocular rosacea, seborrheic blepharitis, keratoconjunctivitis sicca, and chronic punctate corneal epitheliopathy.

CONCLUSIONS

Collectively, these problems produce increased risk of infection for wear of any contact lens; and underscore the importance of proper patient selection, education and post-fit monitoring even when hyper-oxygen transmitting silicone hydrogels are utilized.

Microbial Keratitis in Prospective Studies of Extended Wear With Disposable Hydrogel Contact Lenses

PURPOSE

To report the annualized incidence of microbial keratitis with extended wear of low oxygen transmissible (Dk/t) disposable soft contact lenses from prospective postmarket clinical trials.

METHODS

Seven hundred ninety subjects were enrolled at the L.V. Prasad Eye Institute (LVPEI), Hyderabad, India from March 1993 to March 2000, resulting in 1231 patient eye years, and 167 subjects were enrolled at the Cornea and the Contact Lens Research Unit (CCLRU), Sydney, Australia from July 1987 to December 1999, resulting in 842 patient eye years.

RESULTS

The annualized incidence of microbial keratitis per 10,000 eyes per year of lens wear was 32.5 (95% CI 8.9 to 83.2) for LVPEI, 23.8 (95% CI=2.9 to 85.8) for CCLRU; when data are combined across both centers, the incidence was 28.9 (95% CI=10.6 to 63) per 10,000 eyes per year of lens wear. This equates to 57.0 per 10,000 wearers or 1 in 173 wearers per year of lens wear. All events were rated as slight to moderate in severity and did not result in visual loss. Two events were described to highlight the challenges in diagnosis and treatment of microbial keratitis.

CONCLUSIONS

The incidence of microbial keratitis with extended wear of low-Dk/t disposable lenses was higher in these prospective studies (1 in 210 wearers per year at CCLRU and 1 in 154 wearers per year at LVPEI) than that seen in retrospective population-based surveillance studies (1 in 500 wearers per year). Practitioners and patients should always be alert to signs and symptoms, and practitioners should adopt conservative strategies for diagnosis and management of contact lens-related adverse events.

Bacterial Populations on Silicone Hydrogel and Hydrogel Contact Lenses after Swimming in a Chlorinated Pool

PURPOSE

A number of reports have indicated an association between swimming with contact lenses and subsequent eye infection. This study tests whether a hydrophilic contact lens worn while swimming accumulates bacteria present in the water. It was of interest to determine whether lens type (silicone hydrogel vs. hydrogel) affected the result.

METHODS

Fifteen healthy noncontact lens wearers swam for 30 minutes with a silicone hydrogel lens (PureVision, Bausch & Lomb, Rochester, NY) on one eye and a hydrogel lens (Acuvue 2, Vistakon Inc., Jacksonville, FL) on the other. Lenses were removed aseptically and placed in sterile vials 10 minutes after the subjects left the water. Microbial growth was enumerated for total numbers of colonies and categorized by species present. Numbers of colonies were compared between the two lens groups and with a water sample taken from the pool at the time of the experiment. Eight of the subjects returned on a different day and wore new lenses for 50 minutes in normal room conditions.

RESULTS

Two lenses were lost while swimming. Twenty-seven of the remaining 28 lenses worn while swimming showed colonization, principally with Staphylococcus epidermidis, which was also by far the most common species identified from the water itself. Small numbers of Staphylococcus aureus and Streptococcus salivarius were also present in the water and on the lenses. Numbers of colonies varied among subjects (range, 0 to 230), but no differences were observed between the two lens groups. Lenses removed after 30 minutes of wear without swimming were mostly sterile, with 3 of 16 lenses showing just two colonies each.

CONCLUSION

It appears that wearing a hydrophilic lens while swimming allows accumulation of microbial organisms on or in the lens, regardless of lens material. Swimmers should be advised to wear tight-fitting goggles if lenses are worn while swimming, and thorough disinfection of the lenses before overnight wear seems prudent.

Hypoxia increases corneal cell expression of CFTR leading to increased Pseudomonas aeruginosa binding, internalization, and initiation of inflammation

PURPOSE

To investigate the effect of hypoxia-induced molecular responses of corneal epithelial cells on the surface of rabbit and human corneas and corneal cells in culture on interactions with Pseudomonas aeruginosa that may underlie increased susceptibility to keratitis.

METHODS

Organ cultures of rabbit and human corneal tissue, primary rabbit and human corneal cells, and transformed human corneal cells from a patient with cystic fibrosis and the same cell line corrected for expression of wild-type cystic fibrosis transmembrane conductance regulator (CFTR), the cellular receptor for P. aeruginosa, were exposed to hypoxic conditions for 24 to 72 hours. Changes in binding and internalization of P. aeruginosa were measured using cellular association and gentamicin-exclusion assays, and expression of CFTR and activation of NF-kappaB in response to hypoxia were determined by confocal laser microscopy and quantitative measurements of NF-kappaB activation.

RESULTS

Hypoxia induced in a time- and oxygen-concentration-dependent manner increased association and internalization of clinical isolates of P. aeruginosa in all cells tested. Hypoxia increased CFTR expression and NF-kappaB nuclear translocation in rabbit and human cells with wild-type CFTR. Corneal cells lacking CFTR had reduced NF-kappaB activation in response to hypoxia. Hypoxia did not affect the increase in corneal cell CFTR levels or NF-kappaB activation after P. aeruginosa infection.

CONCLUSIONS

Hypoxic conditions on the cornea exacerbate the binding and internalization of P. aeruginosa due to increased levels of CFTR expression and also induce basal NF-kappaB activation. Both of these responses probably exacerbate the effects of P. aeruginosa infection by allowing lower infectious doses of bacteria to induce disease and promote destructive inflammatory responses.

Forms of vision correction: demographic factors in patient attitudes and perceptions

PURPOSE

To evaluate attitudes toward current treatments for vision correction in a clinical population of adults wearing spectacles and contact lenses (CLs).

METHODS

Patients seen in the Indiana University Contact Lens and Primary Care Clinics in the spring of 2002 completed multiple-choice questionnaires evaluating their current device for vision, comfort, convenience, health and safety, cost, and overall satisfaction. They also rated their interest in and the convenience and health and safety of 30-day continuous wear (CW), 7-day extended wear (EW), modern orthokeratology, and LASIK and were given a forced choice on their preferred method of vision correction.

RESULTS

Three hundred forty-nine CL and 177 primary care patients completed questionnaires. Subjects reported high satisfaction with their current treatment. Seventy percent of glasses wearers were neutral or not interested in CLs or LASIK. CL patients were interested or very interested in orthokeratology (70%) followed by LASIK (65%), 7-day EW (51%), and 30-day CW (44%). Age and sex were the most significant factors that influenced wearing practices and attitudes, with males (especially young) indicating significantly higher use of EW than females (P = 0.0005, chi(2)). Males were also more interested in 7-day EW (P = 0.011) and 30-day CW (P = 0.001) and rated their health and safety higher (P = 0.045 and P = 0.003, respectively).

CONCLUSIONS

In the spring of 2002, many of these patients remained cautious about the health and safety of 7-day EW and 30-day CW CLs.

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.

Relative primary adhesion of Pseudomonas aeruginosa, Serratia marcescens and Staphylococcus aureus to HEMA-type contact lenses and an extended wear silicone hydrogel contact lens of high oxygen permeability

PURPOSE

To compare multiple strains of Pseudomonas aeruginosa and representative isolates of Staphylococcus aureus and Serratia marcescens for their relative primary adhesion to a high Dk silicone hydrogel lens (36% H2O) with that of a HEMA-type lens (58% H2O).

METHODS

A radiolabeled cell procedure with a 2-h cell exposure was employed for enumerating bacteria on unworn and worn silicone hydrogel (balafilcon A) and HEMA-type (etafilcon A) hydrogel lenses.

RESULTS

The degree of primary adhesion of P. aeruginosa to 7-day worn balafilcon A lens was similar to the degree of adhesion to unworn balafilcon A lenses. The degree of primary adhesion by clinical strains to unworn balafilcon A lenses and etafilcon lenses was strain variable, but did not differ markedly for the two lenses with a given strain of P. aeruginosa. Relative to most of the pseudomonad strains, adhesion to the hydrogel lenses by S. aureus and S. marcescens was non-significant.

CONCLUSION

Adhesion of strains of P. aeruginosa to a hydrogel contact lens does not appear to differ appreciably between the HEMA-type etafilcon A and the high Dk silicone hydrogel balafilcon A lens.

Pseudomonas Keratitis Associated With Continuous Wear Silicone-Hydrogel Soft Contact Lens

PURPOSE

To report a case of Pseudomonas aeruginosa culture-positive microbial keratitis in a patient wearing continuous-wear silicone hydrogel soft contact lenses.

METHODS

A 23-year-old white woman in good health had been wearing silicone hydrogel (lotrafilcon A) soft contact lenses continuously for 26 days when she was examined for a corneal ulcer in her left eye. She had given a history of water jet skiing and diving while wearing her contact lenses. Scrapings of the corneal ulcer were positive for P. aeruginosa, and the patient was treated with fortified topical cefazolin and gentamicin for 1 week and subsequently with topical ciprofloxacin for 2 weeks.

RESULTS

The microbial keratitis resolved with successful treatment. However, the patient had a residual visual deficit secondary to stromal scarring.

CONCLUSIONS

The recently introduced continuous-wear silicone hydrogel soft contact lenses, with their hyper oxygen permeability (Dk), have been shown to overcome hypoxia-associated complications and to have less P. aeruginosa binding to the corneal epithelium. Our case shows that sight-threatening microbial keratitis can still occur even with silicone hydrogel soft contact lenses. Contact lens practitioners should educate patients on the risk of sight-threatening microbial keratitis, the need for patient compliance, and prompt assessment of contact lens-related complaints.