Extended-wear Contact Research Articles

The Incidence of Microbial Keratitis among Wearers of a 30-Day Silicone Hydrogel Extended-Wear Contact Lens

To estimate the incidence of presumed microbial keratitis with and without loss of visual acuity among wearers of a silicone hydrogel contact lens (Lotrafilcon A, Night & Day, CIBA Vision, Inc., Duluth, GA), recently approved for up to 30 days of continuous wear. Prospective cohort postmarket surveillance study. Contact lens wearers (recruited from 131 practices) who had been prescribed the lens for intended continuous wear of as many as 30 nights. The occurrence of a corneal infiltrate was ascertained through a combination of center report and direct contact with participants at 3 and 12 months. Whenever a corneal infiltrate was suspected, study and treatment medical records were systematically reviewed by an Endpoints Committee using a predetermined classification scheme for corneal infiltration. Cases of presumed microbial keratitis were determined based on the constellation of presenting signs and symptoms and clinical course. The incidence of presumed microbial keratitis with and without loss of visual acuity. A total of 6245 participants were recruited between August 13, 2002 and July 2, 2003. Of these, 4999 subjects (80%) completed 12 months of follow-up, and these participants contributed a total of 5561 person years of lens wearing experience. Approximately 80% of participants routinely wore their lenses continuously for 3 or more weeks. The overall annual rate of presumed microbial keratitis was 18 per 10,000 (95% confidence interval (CI): 8.5-33.1). There were 2 cases of presumed microbial keratitis with loss of visual acuity, an annual rate of 3.6 per 10,000 (95% CI: 0.4-12.9), and an additional 8 cases without loss of visual acuity, an annual rate of 14.4 per 10000 (95% CI: 6.1-28.4). The rate of presumed microbial keratitis was lower for users reporting typical wear of 3 or more weeks than for those wearing the lens for less than a 3-week continuous period (P = 0.02). The incidence of loss of visual acuity due to microbial keratitis among users of the silicone hydrogel contact lens was low. The overall rate of presumed microbial keratitis with the wearing schedule of as many as 30 nights was similar to that previously reported for conventional extended-wear soft lenses worn for fewer consecutive nights.

A Review of the Holden–Mertz Criteria for Critical Oxygen Transmission

Holden and Mertz established the foundations for the new generation of silicone hydrogel contact lenses for daily and extended wear in 1984. Absence of lens-induced corneal swelling was their premise and although this was possible with daily wear, the goal with extended wear seemed almost impossible because of the limitation of hydrogel materials. Experience with extended and daily wear of disposable contact lenses during the last 2 decades and, more recently, with silicone hydrogels has led to the reconsideration of the validity of the findings of Holden and Mertz. A pivotal influence on the Holden and Mertz critical Dk/t value for closed-eye lens wear was exerted by two numbers: the no-lens wear corneal edema level (4%) and the silicone lens data point (Dk/t of 182x10, closed-eye edema level of 2.6%). Subsequent publications appear to give a more accurate assessment of the no-lens closed-eye corneal edema level, and there are also more recent measurements of silicone hydrogel lens Dk/t and corneal edema responses. It now appears that the Holden and Mertz criteria for extended-wear critical Dk/t should be revised upwards to at least 125x10.

High risk of keratitis with extended wear contact lenses

High risk of keratitis with extended wear contact lenses

Ionic conductivity in hydrogels for contact lens applications

Biphasic hydrogel polymers are in the forefront of new extended wear contact lens development. In the biphasic hydrogel the objective is to produce co-continuous domains of siloxane units for high oxygen permeability, coupled with hydrophilic units forming aqueous channels for hydraulic and ion mobility. These are distributed in phase separated nano-scale regions such that the material is optically clear while achieving the required properties to maintain corneal health and lens movement.

Contact Lens Assisted Pharmacologically Induced Keratoshaping

To retrospectively evaluate the effectiveness and describe the process of reducing hyperopia with a nonsteroidal antiinflammatory agent and a soft disposable contact lens in postoperative excimer laser patients with consecutive hyperopia. Private practice. This study includes a retrospective analysis of 14 eyes of 12 patients who underwent laser in situ keratomileusis or photorefractive keratectomy and experienced consecutive hyperopia. Patients were treated with a tightly fit, extended-wear contact lens in combination with the use of ketorolac tromethamine 0.5% (Acular) in an attempt to steepen the cornea. Uncorrected visual acuity, manifest refraction, and slitlamp examination were performed on a weekly basis until the desired outcome was achieved or until treatment was discontinued. A total of 78.57% of eyes experienced a decrease in consecutive hyperopia (>or=0.50 diopters [D]) (P = 0.002). The mean dioptric change was 1.05D. A total of 88.89% of eyes experienced an increase in uncorrected visual acuity (>or=1 line) (P < 0.001). The mean increase was three lines of Snellen or Jaeger acuity. The mean number of weeks to see an effect was 1.71 weeks, and the mean number of weeks to achieve endpoint was 8.29 weeks (median, 6 weeks). CONCLUSIONS.: Contact lens-assisted pharmacologically induced keratoshaping is an effective treatment option for patients who experience consecutive hyperopia after laser in situ keratomileusis or photorefractive keratectomy.

Forms of Vision Correction

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

Corneal response to Pseudomonas aeruginosa infection.

Pseudomonas aeruginosa (P. aeruginosa) is a common organism associated with bacterial keratitis, especially in those who use extended wear contact lenses. Recent advances in our understanding of host innate and adaptive immune responses to experimental infection have been made using a variety of animal models, including inbred murine models that are classed as resistant (cornea heals) vs. susceptible (cornea perforates). Evidence has been provided that sustained IL-12-driven IFN-gamma production in dominant Th1 responder strains such as C57BL/6 (B6) contributes to corneal destruction and perforation, while IL-18-driven production of IFN-gamma in the absence of IL-12 is associated with bacterial killing and less corneal destruction in dominant Th2 responder strains such as BALB/c. The critical role of IL-1 and chemotactic cytokines such as MIP-2 in PMN recruitment and the critical role of this cell in the innate immune response to bacterial infection is reviewed. Regulation of PMN persistence is also discussed and evidence provided that persistence of PMN in B6 cornea is regulated by CD4+ T cells, while macrophages regulate PMN number in the cornea of BALB/c mice. The studies provide a better understanding of the inflammatory mechanisms that are operative in the cornea after P. aeruginosa challenge and are consistent with long-term goals of providing targets for alternative or adjunctive treatment for this disease. Future studies will be aimed at better defining the role of Toll receptors, neuropeptides (as unconventional modulators of the immune response) and exploitation of disease control by new techniques, such as RNA silencing.

Thygeson's superficial punctate keratitis: Ten years' experience

Purpose To evaluate the presentation, treatment, and disease course of Thygeson's superficial punctate keratitis. Design Observational case series. Participants Forty patients, diagnosed and managed with Thygeson's superficial punctate keratitis between January 1, 1992, and December 31, 2001, on the Cornea Service at Wills Eye Hospital. Methods Retrospective chart review. Main outcome measures Patient demographics, symptoms, visual acuity, ophthalmic examination, management, duration of disease, and length of follow-up. Results At the time of presentation, the mean patient age was 28.7 years. The most common presenting symptoms included photophobia, blurred vision, and irritation. Thirty of 38 patients without a history of decreased vision (78.9%) initially were seen with visual acuities in both eyes of 20/30 or better. The 8 (21.1%) remaining patients all had visual acuities between 20/40 and 20/50; improvement in vision with treatment was noted in all 3 observed at our institution. Six patients (16%) had unilateral disease, whereas another 2 patients had bilateral involvement develop after unilateral presentation. Thirty-nine patients (97.5%) were treated with topical steroids at some point in their disease course. The patient not managed with steroids was only seen once and was managed with artificial tears for mild symptoms. In addition to steroids, a patient was treated for recurrent episodes with extended-wear contact lens, and another patient was started on topical cyclosporine because of an inability to be tapered off topical steroids. The average duration of disease in the 15 patients who were observed for more than a single year was 11.1 years. Conclusions Thygeson's superficial punctate keratitis is a potentially chronic condition, which might affect people of all ages for years to decades. Corticosteroids are the mainstay of treatment, with extended-wear contact lens and topical cyclosporine reserved as secondary agents.

Therapeutic use of Focus Night & Day contact lenses.

To evaluate the safety and efficacy of Focus Night & Day extended-wear contact lenses when used for therapeutic purposes. Fifty eyes of 50 consecutive patients presenting at the Ankara University Medical Center, Cornea and Contact Lens Service, and requiring bandage contact lens use for ocular surface disorders, were enrolled. All patients were fitted with Focus Night & Day contact lenses and were followed in regard to patient satisfaction, contact lens fit and performance, and success of treatment. Twenty-four patients (48%) were male, and 26 (52%) were female. Average age at the time of presentation was 46.9 +/- 21.6 years (range 1.5 to 88 years). Therapeutic contact lens indications included Fuchs' dystrophy (2 eyes), toxic epitheliopathy (1 eye), filamentous keratopathy (2 eyes), corneal perforation (2 eyes), corneal stromal melting (2 eyes), recurrent corneal erosion (4 eyes), chemical or traumatic epithelial defect (3 eyes), epithelial irregularity (1 eye), persistent epithelial defect (4 eyes), lamellar laceration (5 eyes), graft insufficiency (2 eyes), pseudophakic bullous keratopathy (7 eyes), aphakic bullous keratopathy (4 eyes), disciform keratitis (1 eye), postkeratectomy (4 eyes), and post-amniotic membrane transplantation or post-limbal autograft transplantation (6 eyes). Mean duration of continuous contact lens wear was 2.4 +/- 3.0 months (range 3 days to 12 months). At the end of the follow-up period, the mean change in visual acuity was a gain of 1.8 +/- 2.8 logMAR units (0-9 Snellen lines). No sight-threatening complications related to contact lens wear were encountered. A culture-negative sterile corneal infiltrate developed in one patient and was treated with cessation of lens wear and subsequent topical antibiotic and steroids. Focus Night & Day contact lenses are safe and effective when used for therapeutic purposes. Infrequent replacement of these lenses seems to be especially advantageous in patients for whom frequent lens insertion and removal may be associated with epithelial trauma, pain, and a potential increase in infection risk. Infrequent replacement of these lenses also decreased the office time and the cost of treatment without an increase in hypoxia-related complications.

Extended wear contact lenses

Extended wear and continuous wear are synonymous terms that describe a modality of overnight contact lens wear, usually for a period of 1 to 4 weeks. Extended wear of soft contact lenses was first advocated by de Carle in the late 1970s. The first contact lenses approved by the US Food and Drug Administration (FDA) for extended wear were for therapeutic indications [1]. Subsequently, the Permalens (CooperVision, San Jose, California) received approval for extended wear in patients with aphakia in 1978 and the Hydrocuve II-55 in 1980 for cosmetic extended wear [2].

Contact lenses and associated anterior segment disorders: dry eye, blepharitis, and allergy.

Contact lenses should be used with caution in patients who have an ocular allergy. Patients who have seasonal allergy should avoid contact lens use during seasonal flare-ups. The need for clean lenses with minimal deposit buildup must be stressed, and the use of daily wear lenses with rigid disinfecting and cleaning techniques is recommended. Alternatively, daily disposable lenses should be used. The patient should avoid the use of topical anti-allergy agents while the lenses are in place, particularly vasoconstrictor agents. Extended wear contact lenses are contraindicated in patients who have ocular allergy. In general, the use of contact lenses is contraindicated in patients with vernal conjunctivitis. With careful attention to recognizing the patient with ocular allergy, regular monitoring, and patient compliance to lens care, successful contact lens wear can be achieved in most patients with ocular allergy.

Extended wear contact lenses.

Practitioners and patients have been hesitant to use extended-wear contact lenses because of their history of complications; however, there is strong scientific evidence that the hypoxia problems associated with these lenses have been solved. Similarly, clinical evidence shows that the new generation of contact lenses is safe and can be worn without complications for up to 30 days. Patients are now able to wear contact lenses that meet their desire of continuous vision. Both practitioner and patient, however, must be instructed about the signs and symptoms of contact lens complications. Practitioners need to learn about the diagnosis and management of these problems, and patients must be educated about proper eye care, contact lens care, and appropriate follow-up.

Vertical movement of epithelial basal cells toward the corneal surface during use of extended-wear contact lenses.

To study the effects of extended contact lens wear (EW) on the movement of basal epithelial cells toward the corneal surface. Rabbits (n = 32) were injected with 5-bromo-2-deoxyuridine (BrdU) to label a group of proliferating basal epithelial cells, and, 24 hours later, one randomly chosen eye was fitted with a low- or medium-oxygen-transmissible (Dk/t) rigid gas permeable (RGP) contact lens, while the other eye served as the control (n = 28). Four rabbits were not fitted with any contact lens. Rabbits were euthanatized at different time points and the corneal epithelium was immunocytochemically stained for BrdU and/or Ki-67 and counterstained with propidium iodide or Syto 59. Corneal flatmount tissues were examined three dimensionally under a laser confocal microscope and the location of each BrdU-labeled cell in the corneal epithelium (basal or suprabasal) was determined. Four days after injection of BrdU, both low- (P < 0.001) and medium-Dk/t RGP (P < 0.001) lens groups showed significantly more BrdU-labeled cells in the basal cell layer than in the control eyes. Six days after injection of BrdU, a small percentage of BrdU-labeled cells (<0.5%) were Ki-67 positive. Within 6 days, the majority (80%) of BrdU-labeled basal cells became terminally differentiated and rarely divided secondarily in the central epithelium. Short-term use of low- and medium-Dk/t RGP EW contact lenses slows the normal movement of basal epithelial cells toward the surface in the central cornea. This is consistent with known EW-lens-induced decreases in corneal epithelial basal cell proliferation and surface cell exfoliation. Overall, the data suggest that EW lenses significantly inhibit the normal homeostatic turnover rate of the corneal epithelium.

Patterns of mucin adherence to contact lenses.

Contact lens wear alters the preocular fluid through factors that include tear deposits on the lens. In the current study, lens-adherent material was extracted to assess whether contact lenses sample mucins from the preocular fluid. Discarded extended-wear contact lenses were collected from patients with no ocular surface disease. Mucins were extracted in guanidine hydrochloride (GuHCl) with protease inhibitors. After the supernatant was removed, the extraction was repeated twice with the addition of 10 mM dithiothreitol, making a total of three extractions. Mucins were isolated by cesium chloride (CsCl) gradient centrifugation and size fractionated on Sepharose CL2B. Charge distribution was analyzed on ion-exchange chromatography with a lithium perchlorate (LiClO(4)) gradient. Contact lens-adherent mucins comprised soluble mucins and mucins that required solubilization by (repeated) dithiothreitol treatment. MUC1, MUC4, MUC2, and MUC5AC mucins eluted mainly at low buoyant densities in extractions from lenses worn long term without disinfection and at successively higher buoyant densities from monthly disposable contact lenses. Mucins with little negative charge, which were observed in all extractions, and very highly negatively charged species, present in the second and third extractions from contact lenses, had no equivalents in tissue-extracted mucins. Mucins adhering to contact lenses are altered forms of intracellular mucins. Different degrees of adherence of mucins to contact lenses may occur, either because of mucin characteristics or after mucin complexation with adherent materials. In the context of good contact lens hygiene, their presence may offer some protection from toxicants in the tear film, because mucins could function as acceptors for charged moieties such as free radicals.

Role of oxygen in corneal epithelial homeostasis during extended contact lens wear.

Infectious corneal ulcers are seldom observed in healthy, normal eyes. Even exposing normal animal corneas to highly concentrated bacterial suspensions will not result in corneal infection.' Thus, there is evidence that the ocular surface defense system efficiently protects the eye. However, having a contact lens on the ocular surface for prolonged time impairs and alters this defense system. As a consequence, the risk of corneal infection increases, depending partially on contact lens wearing schedule, type, and oxygen transmissibility. Although the development of corneal infection is a multifactorial process, one crucial step in the pathogenesis is the penetration of microorganisms through the tightly compacted multicellular layer structure of the corneal epithelium. Based on that knowledge, we have hypothesized that maintaining a healthy functioning corneal epithelium during contact lens wear is an important and integral part in preventing and reducing the risk for infection. This review summarizes our current understanding of the corneal epithelium and its homeostasis in normal eyes during extended contact lens wear and hypoxia.

Tear turnover and immune and inflammatory processes in the open-eye and closed-eye environments: relationship to extended wear contact lens use.

Tear turnover and immune and inflammatory processes in the open-eye and closed-eye environments: relationship to extended wear contact lens use.

Corneal Thickness Results in the Menicon Z 30-Day Continuous Wear and ACUVUE 7-Day Extended-Wear Contact Lens Clinical Trial

This study was conducted to measure the corneal thickness changes associated with wearing 30-day tisilfocon A (Dk = 163) and 6-day etafilcon A (Dk = 28) contact lenses. The probable cause of the outcomes is discussed. Thirty subjects were fitted with Menicon Z rigid gas-permeable (RGP) contact lenses and a control group (n = 30) was fitted with ACUVUE hydrogel lenses, at two study sites. After a 2-week period of daily wear, subjects began prolonged wear. Measurements were performed at the dispensing visit, and then at the 2-week daily wear, the 1-week, 6-month, and 12-month extended- and continuous-wear visits. Repeated measures analysis of covariance was performed on mean corneal thickness. There was a significant increase in corneal thickness in the hydrogel lens extended-wear group compared to the RGP group (P = 0.03). The mean corneal thickness in the ACUVUE group was 2.58% higher at the 2-week daily wear visit, 2.38% higher at the 1-week extended-wear visit, 2.96% higher at the 6-month, and 2.97% higher at the 1-year visit compared to the RGP continuous-wear patients. Patients wearing high-Dk RGP contact lenses for continuous wear may have thinner corneas (within the normal thickness range) probably because of minimal hypoxia-induced corneal stromal swelling; RGP-induced reversible corneal epithelial compression; deceased epithelial sloughing; or long-term contact lens-induced keratocyte apoptosis. Patients wearing hydrogel contact lenses for extended wear may have thicker corneas because of hypoxia-induced corneal stromal swelling. Additional evidence of corneal hypoxic stress is seen in the higher prevalence of striae and epithelial microcysts in the hydrogel group and greater variability of corneal thickness measurements in the soft contact lens group in our results.

Corneal variations produced by soft extended-wear contact lenses

Using keratometry, we evaluated corneal variations due to use of soft extended-wear contact lenses. Fifty subjects were fitted with either PureVision contact lenses (36% hydration) or Focus Night&Day contact lenses (24% hydration). Results showed decreased horizontal and vertical corneal curvature radii at 0° and 90° 1 day after lens fitting. Variations in corneal curvature radius were greater with these extended-wear lenses than with other types of soft contact lenses.

Spherical indentations of human and rabbit corneal epithelium following extended contact lens wear.

Mucin balls appear to cause spherical indentations in the corneal epithelium during silicone hydrogel extended contact lens wear. The purpose of this report is to describe and quantify these spherical indentations, as examined in the human cornea by in vivo confocal microscopy and by in vitro immunocytochemistry in the rabbit cornea. Confocal images of full-thickness corneal epithelium were taken from three human patients participating in a 1-year extended contact lens-wear trial. Diameter and depth of the indentations were determined and measured. Two rabbit corneas showing identical indentations were stained with propidium iodide (nuclear stain) and Ki-67 (proliferation marker) and were examined using a laser scanning confocal microscope. The diameter of the spherical indentations is largest on the epithelial surface, ranging from 33.9 to 78.8 microm. Indentations form spherical sections whose depth variably extends into the corneal epithelium, reaching as far as the basal lamina. The rabbit model showed no epithelial nuclei within the indentation. Furthermore, stromal cells localized immediately beneath the indentations were positive for Ki-67 (proliferation). Spherical indentations of the corneal epithelium induced by mucin balls appear to be gaps or holes that can extend deep into the corneal epithelium. Indentations may potentially open a pathway for infectious microorganisms to penetrate the cornea. Surprisingly, stromal cells immediately beneath the holes were stimulated to proliferate, and there seemed to be an increase in localized cell density.

Polyclonal human antibodies reduce bacterial attachment to soft contact lens and corneal cell surfaces

Bacterial keratitis due to Pseudomonas aeruginosa is a potentially serious complication of extended-wear contact lens use. Adhesion of P. aeruginosa to soft contact lens materials or corneal endothelial cells in the presence of pooled human immunoglobulins and/or neutrophils in artificial tear fluid was studied in vitro as a potential method to treat contact lens-associated infection. Soft hydrophilic contact lens materials equilibrated in sterile saline were soaked in artificial tear fluid for 18 h prior to use. P. aeruginosa IFO 3455 was added to groups of lenses or confluent cultured bovine corneal endothelial cells with varying amounts of human polyclonal immunoglobulin (IgG) and human blood neutrophils or serum albumin as a control. After 2 or 4 h incubation, adherent viable bacteria on lenses were quantified. Fluorescence microscopy was used to assess bacterial adherence to bovine corneal endothelial cells in the presence and absence of IgG and neutrophils. Various concentrations of albumin had no effect on adhesion. Human immunoglobulin solutions (25 mg/ml) reduced P. aeruginosa adhesion by nearly 1 log and 2 logs after 2 and 4 h incubations, respectively. Neutrophils in combination with 25 mg/ml IgG reduced bacterial adhesion approximately 1 log over reduction in adhesion by neutrophils alone. Diluted human IgG (10 mg/ml) did not significantly decrease bacterial adhesion after 2 or 4 h, but did reduce adhesion in combination with human neutrophils at both time points. Similar reductions in amounts of fluorescently labeled bacteria adhered to cultured monolayers of corneal endothelial cells under these conditions were qualitatively observed.