SciCombinator

Discover the most talked about and latest scientific content & concepts.

Journal: Eye & contact lens

28

: 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.

Concepts: Cornea, Contact lens, Contact lenses

28

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.

Concepts: Archaea, Bacteria, Fungus, Cornea, Microorganism, Contact lens, Contact lenses, Keratitis

28

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.

Concepts: Epidemiology, Eye, Cornea, Lens, Contact lens, Contact lenses, Keratitis, Corrective lens

27

ABSTRACT:: Since the initial launch of silicone hydrogel lenses, there has been a considerable broadening in the range of available commercial material properties. The very mobile silicon-oxygen bonds convey distinctive surface and mechanical properties on silicone hydrogels, in which advantages of enhanced oxygen permeability, reduced protein deposition, and modest frictional interaction are balanced by increased lipid and elastic response. There are now some 15 silicone hydrogel material variants available to practitioners; arguably, the changes that have taken place have been strongly influenced by feedback based on clinical experience. Water content is one of the most influential properties, and the decade has seen a progressive rise from lotrafilcon-A (24%) to efrofilcon-A (74%). Moduli have decreased over the same period from 1.4 to 0.3 MPa, but not solely as a result of changes in water content. Surface properties do not correlate directly with water content, and ingenious approaches have been used to achieve desirable improvements (e.g., greater lubricity and lower contact angle hysteresis). This is demonstrated by comparing the hysteresis value of the earliest (lotrafilcon-A, >40°) and most recent (delefilcon-A, <10°) coated silicone hydrogels. Although wettability is important, it is not of itself a good predictor of ocular response because this involves a much wider range of physicochemical and biochemical factors. The interference of the lens with ocular dynamics is complex leading separately to tissue-material interactions involving anterior and posterior lens surfaces. The biochemical consequences of these interactions may hold the key to a greater understanding of ocular incompatibility and end of day discomfort.

Concepts: Protein, Interaction, Surface tension, Materials science, Surface, Angle, Hysteresis, Contact angle

25

Subjective symptoms and other eye complications were assessed and retrospectively compared in patients belonging to a proprietary membership system who switched from 2-week frequent replacement (2WFR) wear to daily disposable (DD) lens use.

Concepts: Cornea, Contact lens

25

25

To investigate the incidence of fungal contamination of store disinfectant solutions contained in contact lens storage cases belonging to asymptomatic contact lens users.

Concepts: Cornea, Disinfectant, Myopia, Lens, Contact lens, Corrective lens, Intraocular lens

23

To develop a quality of life (QoL) instrument for patients fitted with Orthokeratology (OrthoK) and other modalities of contact lenses.

Concepts: Cornea, Myopia, Contact lens, Corrective lens

23

To compare, in terms of efficacy, the differences between the use of saline solution and a viscous artificial tear to fill the lens during the first month of orthokeratology wear.

Concepts: Cornea, Myopia, Contact lens

5

The aim of this review is to evaluate the ocular safety of orthokeratology (OrthoK) treatment of myopia correction and retardation.