Presence Of Contact Lens Research Articles

Reduction of disinfection efficacy of contact lens care products on the global market in the presence of contact lenses and cases

ObjectiveSight-threatening infections can be caused by pathogenic micro-organisms colonising the cornea, leading to microbial keratitis (MK). These micro-organisms can be introduced to the eye via improper contact lens use and...

Evaluation of Antimicrobial Efficacy of Non-Preserved Multipurpose Solutions in the Presence of Contact Lenses

Purpose: Non-Preserved Multipurpose solutions (MPS) contact lens care products (CLC) offer intrinsic disinfection efficacy against microorganisms. Few studies have evaluated the efficacy of these products in the presence of contact lenses. ISO 18259 addresses biocide uptake into contact lenses for preserved MPS products, which reduces their efficacy. In this study, we evaluated the disinfection efficacy of products containing either hydrogen peroxide or povidone iodide in the presence of contact lenses against two strains of Acanthamoeba trophozoites and cysts.

In Vitro Antimicrobial Efficacy of Silver Lens Cases Used With a Multipurpose Disinfecting Solution.

PurposeWe evaluate the in vitro antibacterial activity of silver-copolymerized barrel cases compared to nonsilver barrel cases in combination with a multipurpose disinfecting solution (MPDS).MethodsThe ability of silver and nonsilver cases to reduce the number of adherent Gram-positive and Gram-negative bacteria was assessed. Additionally, the efficacy of silver cases along with MPDS was investigated in the presence of organic soil and contact lenses. Contact lens cases were challenged with 106 colony-forming units (CFU)/mL of five bacterial species. Adherent bacteria were dislodged from lens cases and surviving organisms enumerated.ResultsSignificantly lower numbers of microbes were recovered from silver cases compared to controls, for all bacterial strains (P < 0.005). The combination of silver case along with MPDS showed added efficacy against Gram-positive and -negative bacteria with a maximum reduction of 3.00 ± 0.5 Log10 CFU/mL, compared to the efficacy of silver cases alone (1.97 ± 0.4 Log10 CFU/mL). The addition of organic soil and a contact lens resulted in a significant (P < 0.005) decrease (a maximum of 1.68 ± 0.2 log10 CFU/mL) in disinfection efficacy when MPDS and either silver or control cases were used.ConclusionsSilver-copolymerized barrel cases work on conjunction with a hypochlorite producing MPDS in the presence of contact lenses and organic soil to reduce microbial contamination of lens cases.Transitional RelevanceSilver-copolymerized barrel contact lens cases show promising in vitro antibacterial activity against bacterial types commonly implicated in contact lens-related corneal infections. This intervention may limit storage case contamination during use and reduce the frequency of contact lens-related microbial disease.

Antimicrobial Efficacy of Multipurpose Disinfecting Solutions in the Presence of Contact Lenses and Lens Cases.

Objective:The aim of this study was to use antimicrobial efficacy endpoint methodology to determine compatibility of multipurpose disinfecting solutions (MPSs), lens cases, and hydrogel lenses for disinfection (AEEMC) against International Organization for Standardization (ISO)–specified microorganisms and clinical ocular isolates of Stenotrophomonas maltophilia.Methods:Six MPSs (PQ/Aldox 1, 2, and 3; PQ/Alexidine; PQ/PHMB; and PHMB) were challenged against ISO-specified microorganisms and S. maltophilia using the AEEMC test. AEEMC tests were performed with and without balafilcon A, etafilcon A, and senofilcon A lenses in lens cases with organic soil. Exposure times included disinfection time (DT) and 24 hr. Additionally, all six MPSs were challenged with two strains of S. maltophilia, based on the ISO Stand-alone test.Results:The efficacy against bacteria for PQ/Aldox and PQ/Alexidine MPSs was not diminished by the presence of lenses. The efficacy of PQ/PHMB and PHMB MPSs against Serratia marcescens was significantly reduced compared with the no-lens control at DT for at least one lens type. The PHMB MPS with lenses present also demonstrated reduced efficacy against Staphylococcus aureus at DT versus the control. PQ/Aldox MPSs retained activity against Fusarium solani with lenses present; however, all other test MPSs demonstrated reduced F. solani efficacy at DT with lenses present. With lenses, all MPSs showed reduced efficacy against Candida albicans.Conclusions:AEEMC antimicrobial efficacy test results vary based on challenge microorganism, contact lenses, and MPS biocide systems. This study highlights the importance of evaluating MPSs for compatibility with lenses and lens cases.

72 A plasma etching and gravimetric monitoring system (PEGMS) for lipid and protein location studies

Purpose: In the tear film lysozyme makes up approximately 35% of the total protein detected and is widely implicated in contact lens spoilation. It functions primarily as a bacteriolytic enzyme in the innate defense of the ocular surfaces. Recently interest in this protein has focused on its ability to function effectively in the presence of contact lens and care solution products. Method: The classic methods based on its interaction with, and the lysis of, the Grampositive bacterial strainMicrococcus lysodeicticus,measured by turbidity at 450nm, were used to investigate lysozyme antimicrobial activity. In addition a fluorescence-based assay which measures the digestion products from a DQTM lysozyme substrate, with excitation maxima at 494nm and fluorescence emission maxima at 518nm, was assessed. Results: Disadvantages of turbidity based assayswere apparent. Additionally many studies use egg white lysozymes as a cheaper assay alternative to human sourced protein, but in addition to compositional variation, human and chicken lysozymes differ in enzymatic activity with a 4:1 ratio respectively. Batch to batch variation in lysozyme preparations was also observed. The kinetic fluorescencebased assaywhich was able to detect activity down to 20U/ml was established and was used to assess the effects that extraction techniques and sample preparation have on the outcome of the activity data. Conclusions: An investigation into the true nature and extent of lysozyme denaturation, which is essential to determine the importance of this phenomenon and its impact on tear film anti-microbial function, was facilitated by more sensitive and varied analytical techniques.

Intraocular Pressure Measurements in Relation to Head Position and Through Soft Contact Lenses: Comparison of Three Portable Instruments

to compare the reproducibility of three portable instruments-the Tono-Pen tonometer (Reichert Ophthalmic Instruments, Depew, NY), the Phosphene tonometer (Bausch & Lomb, Rochester, NY), and the TERT (Through Eyelid Russian Tonometer; Rjazan State Instrument Making, Rjazan, Russia)-in the measurement of intraocular pressure (IOP) with and without soft contact lenses and in different head positions. twenty-six eyes of healthy volunteers were examined by the three instruments while the subjects were sitting, recumbent, and hyperextending their heads, and with and without contact lenses. IOP measurements were compared and the effects of head position and presence of contact lenses on the resultant values were analyzed. the average difference between the recumbent and sitting positions was 3.56, 2.68, and 2.62 mm Hg for the Tono-Pen tonometer, Phosphene tonometer, and TERT, respectively. There was an increase of 5.60, 2.78, and 2.63 mm Hg in hyperextension compared to sitting for the Tono-Pen tonometer, Phosphene tonometer, and TERT, respectively. The difference in the IOP values obtained in the presence and absence of therapeutic contact lens for the three instruments in the three positions was between -1.23 and +1.47 mm Hg. IOP measurements of bedridden patients are only slightly higher than those of sitting patients except for the Tono-Pen tonometer in the hyperextension position. The presence of contact lenses does not affect IOP values obtained by the three evaluated instruments.

Toward the next generation of iris biometrics science

Iris biometrics involves using the pattern of texture in the iris, the colored region of the eye surrounding the pupil, to verify a person’s identity. The field originated in the work of John Daugman,1, 2 and, in recent years, heightened global and domestic security concerns have lead to an increased interest in iris biometric technology in academia, industry, and government.3 The field promises highly accurate identity verification, but a more flexible user interface is required. However, this could lead to less well-controlled image acquisition, so there is also a need for new techniques to handle a broader range of image quality. To this end, we have been supporting the US Government’s Iris Challenge Evaluation programs4 and the current Multiple Biometric Grand Challenge program,5 as well as conducting our own basic research on iris biometrics.6–8 Many factors complicate the use of iris biometrics, such as differences in pupil dilation, the presence of contact lenses, and the eye’s natural aging. Figure 1 shows an example of the type of image used. Current systems largely ignore differences in pupil dilation. They also assume that the natural aging of the eye has no effect on accuracy. Commercial technology can handle some problems that arise with contact lenses, for example, but our research suggests that there are more common, subtle, and smaller effects that are currently ignored. Iris biometrics works best when the pupil is not strongly dilated, and when the degree of dilation is similar in the image used to enroll a person in the system and the image used for verification. The conventional approach ignores differences in pupil dilation and simply converts a region from the iris image into a standard size, and then creates a corresponding binary ‘iris code‘ based on the texture pattern. In current systems of this type, pupil dilation information is discarded. Figure 1. Example iris biometrics image. The eyelids occlude the upper and lower parts of the iris. A shadow is cast on the lowest visible portion, and a specular reflection is seen at the top center of the visible portion. All of these factors complicate iris image analysis.

The Long and Winding Road: Contact Lens-induced Ptosis

Intrapalpebral migration is a rare complication of hard contact lens use. We report a case of a 52-year-old man who presented with right upper eyelid ptosis and requested cosmetic correction. He had no ocular history apart from myopia, which was corrected with the use of hard contact lenses. Prior to the ptosis he recalled losing his right contact lens during a bout of sneezing. He replaced the missing lens and continued to wear contact lenses as usual. After careful clinical examination, an ipsilateral small, mobile eyelid mass was detected, and orbital MRI verified the suspected presence of a hard contact lens. Following surgical removal and ptosis correction, the patient made a full recovery. The phenomenon of hard contact lens migration in the periocular tissues has been reported in the literature before, but most patients experienced symptoms of variable severity. In this patient, however, there were no symptoms to indicate the presence of a contact lens. This case highlights the importance of including intrapalpebral contact lens migration in the differential diagnosis of an eyelid mass or ptosis in patients.