pH of multipurpose contact lens solutions over time.

The pH of nine different brands of multipurpose contact lens solutions available in Spain was determined over a period of 32 days after opening the bottles. Five bottles of nine solutions were used, each of which was buffered and obtained from different manufacturers. The pH measurements were taken using a micropH 2002 Crison pH-meter (accuracy +/- 0.001 pH units). Each solution was measured three times daily over the test period using 10-ml samples taken from the same container. Fluctuations in pH over time were observed but these were within the range of ocular comfort. The average pH of all the solutions tested proved to be between 6.99 and 7.56.     

Osmolality and buffering agents in soft contact lens packaging solutions.

AIM: The study determined the effects of packaging solution osmolality and buffering agent on soft contact lens parameters. METHODS: One lens type from each FDA contact lens material category was equilibrated to phosphate buffered saline (PBS) or borate buffered saline (BBS), at three osmolality concentrations: 270, 310 and 414 mOsmol/kg. Lens diameter (LD), base curve (BOZR) and back vertex power (BVP) were measured and compared to nominal packaging label values. RESULTS: Statistically significant differences were found in all three parameters across all osmolality levels for both buffering agents. Etafilcon A showed the largest amount of parameter change, followed by alphafilcon A and balafilcon A. Lotrafilcon A was the least affected. LD of alphafilcon A lenses (greater than +/- 0.2 mm) and BVP of lotrafilcon A and etafilcon A lenses (greater than +/- 0.25 D) measured outside the International Standards Organization (ISO) tolerance from their packaging labels when measured in solutions that mimicked their packaging solutions. CONCLUSION: Osmolality and buffering agents influence lens parameters. Packaging solutions can vary the parameters of some lens types from their nominal value to outside the tolerance range set by ISO.     

Antibacterial and antifungal effects of soft contact lens disinfection solutions.

AIMS: To study the antibacterial and antifungal effects of soft contact lens disinfection solutions. METHODS: Eight contact lens disinfection solutions containing hydrogen peroxide or biguanides or polyquad compounds were evaluated with respect to their ability to disinfect a saline solution experimentally contaminated with different bacteria and with a fungus. We used cultures in blood Agar, MuellerHinton agar and Saboureaud's agar to identify the bacterial and fungal growth following 14 h of exposure to the disinfection solutions. RESULTS: Hydrogen peroxide, DYMED and polyhexamide solutions prevented the growth of the four bacteria studied. The solution containing biguanide prevented the growth of Escherichia coli and Staphylococcus epidermidis. The solution with polyquad solution only prevented the growth of Staphylococcus epidermidis and none of the disinfection solutions prevented the growth of Candida albicans. The control solution, which was saline, did not prevent the growth of either bacteria or fungi. CONCLUSIONS: Disinfection solutions containing hydrogen peroxide, or DYMED or polyhexamide can disinfect these four bacteria but none of them prevented the growth of Candida albicans.     

Clinical comparison of three polyhexanide-preserved multi-purpose contact lens solutions.

This study investigated the clinical differences between three commercially available polyhexanide (PHMB) preserved disinfection systems containing varying percentages of PHMB, when used with FDA group II and group IV disposable contact lenses. After 1 month of wear the product with the highest concentration of PHMB ('All-in-One') was graded as being less comfortable on insertion (P<0.003), had lower overall satisfaction (P<0.05) when compared with the other two products. Corneal staining was also significantly higher with this product after both 14 days (P<0.001 with group II and P<0.02 with group IV) and 28 days (P<0.00001 with group II and P<0.03 ith group IV).     

Identification and susceptibility to multipurpose disinfectant solutions of bacteria isolated from contact lens storage cases of patients with corneal infiltrative events

Corneal infiltrative events (CIEs) are being reported with increasing frequency in lens wearers and may be related to specific multipurpose disinfecting solution (MPDS), contact lens type or bacterial bio-burden. Here, the efficacy of MPDS's against bacteria from contact lens storage cases (CLSC) of patients with CIEs was investigated. Eighteen CLSC from patients with CIEs were cultured. All reported using the same MPDS based on PQ-1 + Aldox + nonanoyl-EDTA prior to experiencing CIEs. Bacteria were identified and tested for sensitivity to MPDS-1 and three other MPSDs. 16/18 CLSC (89%) contained bacterial counts of ≥10⁴–10⁸/mL. Achromobacter spp. was most frequently identified and was found in 11/18 cases (61%). This was followed by 4/18 (22%) Stenotrophomonas maltophilia, 3/18 (17%) Serratia marcescens, 3/18 (17%) Delftia spp., 2/18 (11%) Elizabethkingia spp., 2/18 (11%) Chryseobacterium indologenes and 1/18 Sphingobacterium spiritivorum. Acanthamoeba was not isolated. All of the Achromobacter strains were resistant to MPDS-1 with <1 log₁₀ kill up to 14 days exposure and the solution also showed reduced efficacy against the other isolates at the manufacturer's recommended disinfection time of 6 h. Two strains of S. maltophilia and Delftia spp. grew in the solution over 14 days. Factors responsible for causing adverse events such as CIEs in contact lens wearers remain unclear. However, the presence of significant bio-burden in the contact lens storage case and lens may initiate an immunological response resulting in CIEs either directly or through the release of endotoxins (e.g. lipopolysaccharides) from the bacterial outer cell membrane.     

The refractive index of contact lens saline solutions

PurposeThe aim of this study was to measure the refractive index of three readily available contact lens saline solutions in order that these values could be used in a calculation to convert back vertex power measured in saline to its corresponding power in air.MethodUsing an automatic digital refractometer, measurements were made daily for 31 days at 20 °C and at a wavelength of 589.3 nm of the refractive index of fifteen bottles from different manufacturing batches of each of the three saline solutions.ResultsFor AMO LENS PLUS™ OcuPure™, BAUSCH & LOMB Sensitive Eyes™ Plus Saline Solution and Sauflon saline, the mean values of refractive index were 1.33458, 1.33465 and 1.33470, respectively. The standard deviation for each solution was 0.00001 and the range of the measured values of refractive index of the three solutions over the test period did not exceed 0.00005.ConclusionsIt is proposed that when calculating back vertex power in air from measurements made in a wet cell that refractive index values for AMO LENS PLUS™ OcuPure™, BAUSCH & LOMB Sensitive Eyes™ Plus Saline Solution and Sauflon saline of 1.3347, 1.3348 and 1.3348, respectively be used for focimeters operating at a wavelength of 587.56 nm and values of 1.3361, 1.3362 and 1.3362, respectively when a wavelength of 546.07 nm is used.     

Comparative study of pH for different saline and multi-purpose contact lens solutions.

In this study, we determined the pH of different saline and multipurpose contact lens solutions available on the Spanish market. We examined 10 samples of 14 solutions, seven of which are saline solutions and seven multipurpose ones, from different manufacturers. Both types of solution were found to have significant variations in pH, with values ranging from 6.70 to 7.57 for the saline solutions and 6.84 to 7.63 for the multipurpose solutions. We concluded that the solutions should not affect the ocular physiological performance because their pH values are within the buffering capacity of the eye.     

Re-wetting, comfort, lubricant and moisturizing solutions for the contact lens wearer.

In recent years there have been significant changes in perspective and availability of eyedrops designed to provide comfort to the contact lens wearer. This review addresses the reasons why there is a need for these types of products and considers their potential impact on the corneal and conjunctival surface. The methods of assessment of these solutions are discussed and the range of current products and options for the UK practitioner are detailed.     

Videokeratoscopy in contact lens practice.

Videokeratoscopy is an important addition to contact lens practice, where a better understanding of corneal contour obviously helps the practitioner to achieve an optimal fitting relationship between the contact lens and the cornea. A variety of topographical maps, encompassing a large range of corneal conditions, are presented in this study to illustrate the different corneal contours the contact lens clinician is likely to encounter in practice. Interpretation of these corneal maps is outlined, with an emphasis on how one determines the appropriate contact lens fitting strategy based on the videokeratoscopic image.     

Antiviral effect of multipurpose contact lens disinfecting solutions against coronavirus

PurposeTo evaluate the antiviral potential of five multipurpose disinfecting solutions against coronavirus (mouse hepatitis virus, a surrogate for SARS-CoV-2 human corona virus).MethodsTest solutions (Biotrue, renu Advanced [Bausch and Lomb], ACUVUE RevitaLens [Johnson and Johnson Vision], cleadew [Ophtecs corp.] or AOSept Plus [Alcon]) were mixed with the coronavirus mouse hepatitis virus at 10⁴ plaque forming units (PFU)/mL as the final concentration and incubated at room temperature for the specified disinfection time. Surviving virus from each sample was then quantified by standard plaque forming unit assay and the reduction of PFU for each disinfectant was compared to the phosphate buffer saline (PBS) treated negative control. A regimen test was also conducted using Biotrue.ResultsThe three multipurpose disinfecting solutions Biotrue (containing PHMB and polyquaternium-1), renu Advanced (PHMB, polyquaternium-1 and alexidine) and ACUVUE RevitaLens (polyquaternium-1 and alexidine) did not kill the coronavirus at the manufacturers recommended disinfection time in the stand alone test. After treatment, the virus’s titer (3.8 ± 0.2 log₁₀ for Biotrue, 3.7 ± 0.1 log₁₀ for renu and 3.7 ± 0.2 log₁₀ for RevitaLens) was similar to the negative control (3.7 ± 0.1 log₁₀; p ≥ 0.996). AOSept Plus (hydrogen peroxide) and cleadew (povidone iodine) significantly (p < 0.001) reduced the numbers of coronaviruses to below the detection limit (i.e. killed 3.7 ± 0.1 log₁₀ viruses compared to control). However, there was a significant reduction (p = 0.028) in numbers of coronaviruses attached to lenses when using the regimen test with Biotrue.ConclusionsThis study shows that oxidative contact lens disinfecting solutions (i.e. those containing povidone-iodine or hydrogen peroxide) provide superior antiviral activity against a coronavirus surrogate of SARS-CoV-2, unless the full regimen test (rub, rinse, disinfect) is used.     

Effects of multipurpose contact lens solutions on the protein composition of the tear film.

OBJECTIVES: To analyze the influence of multipurpose contact lens cleaning solutions on tear proteins. Changes in tear film protein profiles of contact lens wearers who used several marketed brands of multipurpose contact lens care solutions, were assessed by ProteinChip analysis. METHODS: Three studies were conducted. Study I was a comparison of Complete and OptiFree multipurpose solutions. Study II was a study with Complete Moisture Plus solution, Study II was a comparison of Renu and Solocare contact lens solutions. Wearers of soft contact lenses were assigned to use the contact lens care solutions for 4 weeks. Non-contact lens wearing patients were used as controls. Tear samples of each participant were analyzed with the ProteinChip (SELDI-TOF) system. Multivariate statistical analysis and artificial neural networks were used to determine the tear protein profiles of each study group. RESULTS: Before starting the use of the solutions, the tear protein composition in all contact lens wearers deviated from the tear composition of the non-contact lens wearing controls. After 4 weeks of using the different care regimens, the tear protein composition of the patients using Complete or Complete Moisture Plus solutions tended to move toward that of the non-contact lens wearing controls. The tear protein composition of patients using the OptiFree, Renu or Solocare solutions did not undergo a measureable change in the protein level. CONCLUSIONS: The ProteinChip system can analyze protein profiles for large-scale applications as in clinical studies. Two multipurpose solutions, Complete and Complete Moisture Plus, demonstrated a beneficial effect on the tear proteins in contact lens wearers.     

Osmolality and pH of commercially available contact lens care solutions and eye drops

PurposeThe physical properties of contact lens care solutions and Eye Drops (ED) may affect initial comfort and dry eye symptomatology in contact lens wearers, although these properties are not always provided by manufacturers. The present study aimed to measure and compare the osmolality and pH of commercially available contact lens care solutions and ED.MethodsForty-four solutions were tested (17 lens care solutions and 27 ED) and classified by the presence and/or combination of the viscosity/lubrication-enhancing ingredients. Solution osmolality was obtained with the Fiske 110 osmometer and pH was measured with a micro-pH 2000. Each measurement was taken ten times, following the manufacturer's instructions, while controlling for room temperature and humidity. Differences between the values of the physical properties of the solutions were analysed by type and viscosity/lubrication-enhancing agent subclassification.ResultsOsmolality ranged from 192.6 ± 2.17 to 364.6 ± 2.88 mOsm/Kg, while pH ranged from 6.35 [6.35–6.26] to 7.99 [7.99–8.00]. A significant difference in the osmolality and pH values of contact lens care solutions and ED was found when classified by type or viscosity/lubrication-enhancing agent (ANOVA and Kruskal-Wallis respectively, both p < 0.001).ConclusionsThe physical properties of some contact lens care solutions and ED are not readily available. The osmolality and pH values of various commercially available lens care solutions and ED vary significantly both by type and viscosity/lubrication-enhancing ingredients.     

Hypersensitivity responses and contact lens wear.

Hypersensitivity diseases that involve the eye are common reasons why patients present to eyecare practitioners. Common ocular hypersensitivity disorders include allergic conjunctivitis, giant or contact lens induced papillary conjunctivitis and atopic keratoconjunctivitis. The diagnosis and management of ocular hypersensitivity can present a challenge to eyecare practitioners and an understanding of the mechanisms that underlie the signs and symptoms of such conditions is necessary for their appropriate management. This article reviews the mechanisms by which the eye responds to antigenic challenges, the pathogenesis of ocular hypersensitivity responses, particularly in relation to contact lens wear, and illustrates possible management strategies.     

Investigations on Fusarium spp. and their mycotoxins causing Fusarium ear rot of maize in Kosovo

After wheat, maize (Zea mays L.) is the second most important cereal crop in Kosovo and a major component of animal feed. The purpose of this study was to analyse the incidence and identity of the Fusarium species isolated from naturally infected maize kernels in Kosovo in 2009 and 2010, as well as the mycotoxin contamination. The disease incidence of Fusarium ear rot (from 0.7% to 40% diseased ears) on maize in Kosovo is high. The most frequently Fusarium spp. identified on maize kernels were Fusarium subglutinans, F. verticillioides/F. proliferatum and F. graminearum. Maize kernel samples were analysed by LC-MS/MS and found to be contaminated with deoxynivalenol (DON), DON-3-glucoside, 3-acetyl-DON, 15-acetyl-DON, zearalenone, zearalenone-14-sulphate, moniliformin, fumonisin B₁ and fumonisin B₂. This is the first report on the incidence and identification of Fusarium species isolated from naturally infected maize as well as the mycotoxin contamination in Kosovo.