Concept: Contact lenses
Clinical performance and “ex vivo” dehydration of silicone hydrogel contact lenses with two new multipurpose solutions
- Contact lens & anterior eye : the journal of the British Contact Lens Association
- Published over 8 years ago
To compare the performance of two novel multipurpose disinfecting solutions (MPDS) in preventing silicone hydrogel contact lens dehydration, provide higher scores of subjective comfort and stable optical quality during a month of lens wear in neophyte volunteers.
Keratitis (inflammation of the cornea) can result from contact lens wear or other causes. Keratitis from all causes, including contact lens wear, results in approximately 1 million clinic and emergency department visits annually, with an estimated cost of $175 million in direct health care expenditures in 2010 (1). Approximately 41 million U.S. residents wear contact lenses, and in 2014, >99% of contact lens wearers surveyed reported at least one behavior that puts them at risk for a contact lens-related eye infection (2). The Center for Devices and Radiological Health at the Food and Drug Administration (FDA) regulates contact lenses as medical devices, and certain adverse events related to contact lenses are reported to FDA’s Medical Device Report (MDR) database. To describe contact lens-related corneal infections reported to the FDA, 1,075 contact lens-related MDRs containing the terms “ulcer” or “keratitis” reported to FDA during 2005-2015 were analyzed. Among these 1,075 reports, 925 (86.0%) were reported by a contact lens manufacturer and 150 (14.0%) by an eye care provider or patient. Overall, 213 (19.8%) reports described a patient who had a central corneal scar, had a decrease in visual acuity, or required a corneal transplant following the event. Among the reports, 270 (25.1%) described modifiable factors known to be associated with an increased risk for contact lens-related corneal infections, including sleeping in contact lenses or poor contact lens hygiene; the remainder did not provide details that permitted determination of associated factors. Continued efforts to educate contact lens wearers about prevention of contact lens-related eye infections are needed.
Wearing contact lenses has been identified as a risk factor for the development of eye conditions such as giant papillary conjunctivitis and keratitis. We hypothesized that wearing contact lenses is associated with changes in the ocular microbiota. We compared the bacterial communities of the conjunctiva and skin under the eye from 58 subjects and analyzed samples from 20 subjects (9 lens wearers and 11 non-lens wearers) taken at 3 time points using a 16S rRNA gene-based sequencing technique (V4 region; Illumina MiSeq). We found that using anesthetic eye drops before sampling decreases the detected ocular microbiota diversity. Compared to those from non-lens wearers, dry conjunctival swabs from lens wearers had more variable and skin-like bacterial community structures (UniFrac;P value = <0.001), with higher abundances ofMethylobacterium,Lactobacillus,Acinetobacter, andPseudomonasand lower abundances ofHaemophilus,Streptococcus,Staphylococcus, andCorynebacterium(linear discriminant analysis [LDA] score = >3.0). The results indicate that wearing contact lenses alters the microbial structure of the ocular conjunctiva, making it more similar to that of the skin microbiota. Further research is needed to determine whether the microbiome structure provides less protection from ocular infections.
Contact lens-related eye infections, which can lead to serious outcomes, including blindness, are associated with several risk factors, including sleeping in lenses, exposing lenses to water, not adhering to replacement schedules, and reusing disinfecting solution (1). In some studies, adolescent and young adult contact lens wearers have been reported to be more likely than older adult contact lens wearers to develop eye infections (2,3) and more likely to have poor contact lens hygiene practices (2). In 2015, CDC reported the number and demographics of adult contact lens wearers in the United States to define the population at risk for contact lens-related eye infections (4); however, this estimate did not include adolescents. To better understand this group of younger contact lens wearers and guide prevention efforts, a population-based survey was used to assess contact lens wear, care behaviors, risk factors, and demographics among persons aged 12-17 years (referred to as adolescents in this report), young adults aged 18-24 years, and older adults aged ≥25 years in the United States. In 2016, an estimated 3.6 million adolescents (14.5%) wore contact lenses. Of the adolescents who wore contact lenses, 85% reported at least one behavior that put them at risk for a contact lens-related eye infection, compared with 81% of young adults, and 88% of older adults. These findings can inform the creation of age-specific targeted prevention messages aimed at contact lens wearers and establish a baseline for evaluating trends in contact lens wear, care habits, and contact lens-related risk behaviors.
: The aim was to discuss the use of a conjunctival flap for treatment of keratolysis of a keratoprosthesis (Kpro) donor graft in a patient fitted with a cosmetic contact lens.
: To assess the relationship between the thinnest corneal location and the steepest and maximum elevation corneal locations in subjects with keratoconus and the effect of gas permeable contact lens wear on the location of these points.
PURPOSE:: Microbial adhesion to contact lenses is believed to be one of the initiating events in the formation of many corneal infiltrative events, including microbial keratitis, that occur during contact lens wear. The advent of silicone hydrogel lenses has not reduced the incidence of these events. This may partly be related to the ability of microbes to adhere to these lenses. The aim of this study was to review the published literature on microbial adhesion to contact lenses, focusing on adhesion to silicone hydrogel lenses. METHODS:: The literature on microbial adhesion to contact lenses was searched, along with associated literature on adverse events that occur during contact lens wear. Particular reference was paid to the years 1995 through 2012 because this encompasses the time when the first clinical trials of silicone hydrogel lenses were reported, and their commercial availability and the publication of epidemiology studies on adverse events were studied. RESULTS:: In vitro studies of bacterial adhesion to unworn silicone hydrogel lens have shown that generally, bacteria adhere to these lenses in greater numbers than to the hydroxyethyl methacrylate-based soft lenses. Lens wear has different effects on microbial adhesion, and this is dependent on the type of lens and microbial species/genera that is studied. Biofilms that can be formed on any lens type tend to protect the bacteria and fungi from the effects on disinfectants. Fungal hyphae can penetrate the surface of most types of lenses. Acanthamoeba adhere in greater numbers to first-generation silicone hydrogel lenses compared with the second-generation or hydroxyethyl methacrylate-based soft lenses. CONCLUSION:: Microbial adhesion to silicone hydrogel lenses occurs and is associated with the production of corneal infiltrative events during lens wear.
ABSTRACT:: Contact lens-associated corneal infiltrative events (CIEs) are presumed sterile events that have complicated contact lens wear for more than 30 years. There is consistent evidence that silicone hydrogel soft contact lenses increase CIE risk by twofold compared with low Dk hydrogel materials. The incidence of CIEs during silicone hydrogel extended wear ranges from 2% to 6% for symptomatic events and from 6% to 25% when asymptomatic events are included. For daily wear, with silicone hydrogels, the incidence of CIEs ranges from 2% to 3% for symptomatic events and from 7% to 20% when asymptomatic events are included. Despite the increased rate of CIEs with silicone hydrogels, the benefits of these lenses largely outweigh this risk for many patients. Most risk factors for CIEs observed with silicone hydrogels are consistent with CIE risk factors reported earlier with hydrogel lenses, such as bacterial bioburden on lens surfaces, and young age among others. Limiting the transfer of bacterial bioburden from the skin to lenses, lens cases and eventually to the eye is an obvious step forward for the prevention of CIEs across all lens types.
Purpose: To alter the composition and structure of silicone hydrogel contact lenses to achieve controlled release of dexamethasone and evaluate the lens optical and mechanical properties compared to commercial lenses. There is a tremendous need for controlled release of drugs from ocular biomaterials as the majority of ophthalmic drugs are delivered via topical eye drops, which have low bioavailability and patient compliance. Methods: Poly(PDMS-co-TRIS-co-DMA) contact lenses were synthesized with varying PDMS/TRIS:DMA ratios (0.25:1, 0.67:1, 1.5:1) as well as with additional crosslinking monomers. Lenses were characterized via in vitro release studies in a microfluidic device at ocular flowrates and in large well-mixed volumes, optical quality studies over visible wavelengths, mechanical analysis, and determination of polymer volume fraction in the swollen state. Results: Extended and controlled release of therapeutically relevant concentrations of dexamethasone was achieved for multiple day, continuous wear up to 60 days at in vitro ocular flowrates. Release was delayed due to a combination of increased hydrophobic to hydrophilic composition and the inclusion of additional structural constraints, both of which decreased the polymer volume fraction in the swollen state. However, decreased mass release rates were at the expense of increased modulus and decreased lens flexibility. All lenses had high optical clarity (∼90% transmittance) and contained highly oxygen permeable siloxane composition similar to those found in commercial silicone hydrogel lenses, but they had poor flexibility for use as soft contact lenses. Conclusions: Based on our results, the lenses described herein likely have too high of a modulus for use as extended-wear, soft contact lenses with drug release. Therefore, other controlled release methods would be better suited for maintaining adequate mechanical properties and achieving controlled and extended release for the duration of wear in soft, silicone hydrogel contact lens biomaterials. However, these biomaterials may find clinical use as more rigid gas permeable contact lenses or inserts.
- Optometry and vision science : official publication of the American Academy of Optometry
- Published about 8 years ago
PURPOSE: The primary purpose of this pilot study was to compare epithelial barrier function (EBF) and staining in a small group of participants using a silicone hydrogel (SH) lens worn on a daily basis with two different care regimens. Secondarily, the aim was to see if there was any correlation between corneal staining and EBF. METHODS: The corneal EBF of 10 non-lens wearers (control) and 15 age-matched asymptomatic SH contact lens wearers (test) were assessed using fluorophotometry. Biomicroscopy was performed to assess corneal staining after the EBF was measured. The lens wearers wore PureVision (FDA group V) SH lenses for two consecutive 1-month periods while using either Alcon Opti-Free Express or Renu Fresh using a randomized, investigator-masked, crossover design. Control subjects were assessed on one occasion, and lens wearers were examined before fitting with lenses and after 7, 14, and 28 days of lens wear, with each combination. RESULTS: Compared with the control group, both study groups had an increase in epithelial permeability at baseline (p ≤ 0.04). There were no changes in EBF during the treatment period for either solution (p = 0.87). A significant difference in EBF was found between the test groups during the treatment period (p = 0.02), with greater permeability in the Renu Fresh-disinfected lenses. There was poor correlation between corneal staining and EBF (r = 0.35, p > 0.05) because of large individual variations. CONCLUSIONS: Daily wear of highly oxygen-permeable SH lenses increases corneal epithelial permeability to fluorescein probably because of increased mechanical effects. In addition, certain lens-solution interactions can add to this effect, as seen in this study. Despite having a low amount of central corneal staining in the Renu Fresh group, staining and EBF did not prove to be well correlated. The presence of central corneal staining is a confounding factor when measuring EBF.