- Contact lens & anterior eye : the journal of the British Contact Lens Association
- Published almost 5 years ago
PURPOSE: To investigate differences in ocular aberrations induced by centre-near multifocal soft contact lenses (SCL) relative to single vision SCLs and their effect on contrast sensitivity function (CSF). METHODS: Ocular aberrometry was measured in 18 cyclopleged subjects (19-24 years) while wearing Ciba Air Optix low (AOlow) and high (AOhigh) add, Bausch & Lomb PureVision low (PVlow) and high (PVhigh) add multifocals, and a Bausch & Lomb PureVision single vision (PVsv) control with the same -3.00D distance back vertex power. Zernike polynomials were scaled to 4, 5 and 6mm pupils. CSF was measured at equivalent distances of 6m, 1m and 40cm while fully corrected with spherical trial lenses at 6m. RESULTS: AOlow, AOhigh and PVhigh induced a negative shift in primary spherical aberration (Z12) from PVsv and all multifocal SCLs induced a positive shift in secondary spherical aberration (Z24) (all p<0.01), without significantly increasing coma. Area under the CSF (AUCSF) reduced at 40cm for all multifocals relative to PVsv (p<0.05), but was not significantly different at 6m or 1m. A moderate correlation (r=-0.80, p<0.005) was found between changes in Z12 and AUCSF at 40cm for AOhigh, with an increase in negative Z12 reducing multifocal-induced loss of CSF. CONCLUSIONS: Centre-near multifocal SCLs induced a negative shift in Z12 and a positive shift in Z24. Although CSF was unaffected at 6m and 1m it was reduced at 40cm, possibly because changes in Z12 and Z24 were not great enough to induce a significant shift in centre of focus and increase in depth of field.
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.
: 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.
In recent years, Aspergillus species are reported frequently as aetiological agents of fungal keratitis in tropical countries such as India. Our aim was to evaluate the epidemiological features of Aspergillus keratitis cases over a 3-year period in a tertiary eye care hospital and to determine the antifungal susceptibilities of the causative agents. This study included culture proven Aspergillus keratitis cases diagnosed between September 2005 and August 2008. Data including prevalence, predisposing factors and demography were recorded, the isolates were identified by morphological and molecular methods and the minimum inhibitory concentration values of antifungal agents towards the isolates were determined by the microdilution method. Two hundred Aspergillus isolates were identified among 1737 culture proven cases. Most of the aspergilli (75%) proved to be A. flavus, followed by A. fumigatus (11.5%). Sixteen (8%) isolates belonged to species that are recently identified causative agents of mycotic keratitis. Most of the infected patients (88%) were adults ranging from 21 to 70 years of age. Co-existing ocular disease was confirmed in 16.5% of the patients. Econazole, clotrimazole and ketoconazole were notably active against A. flavus. Aspergillus keratitis is a significant problem in patients with ocular lesions in South-Indian States, warranting early diagnosis and initiation of specific antifungal therapy to improve outcome.
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.
To compare the blood agar (BA), sabouraud dextrose agar (SDA) and chocolate agar (CA) for the isolation of fungi in patients with mycotic keratitis. Corneal Scrapings of 229 patients with clinically diagnosed microbial keratitis were inoculated on BA, SDA, CA. The culture media were evaluated for the rate and time taken for the fungal growth. Seventy six of 229 patients had fungal keratitis. Fungus grew on BA in 60/76(78.9 %), on SDA in 76/76 (100 %), on CA in 40/76(52.6 %) patients. The fungi which grew on BA (60/76) also grown on SDA at the same time. The colony morphologies of different fungi were better on SDA than BA/CA. Among the different culture media, SDA is essential for the isolation fungi in patients with mycotic keratitis.
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.