Contact Lens Solutions Research Articles

A Clinical Evaluation of a Multipurpose Soft Contact Lens Solution: Unicare

A three-month study was conducted to establish the safety and efficacy of Unicare® - a multi­purpose soft contact lens solution. Patient accep­tance of the solution was good in spite of one case of an adverse ocular response among the twenty-one subjects evaluated.

Extraction-fluorimetric determination of mercury with 2-phenylbenzo[8,9]quinolizino[4,5,6,7-fed]phenanthridinylium perchlorate

The characteristics of 2-phenylbenzo[8,9]quinolizino[4,5,6,7-fed] phenanthridinylium perchlorate (PQPP) as a reagent for the formation of ion-association complexes with metal-bromide anions and its application to the fluorimetric determination of mercury are described. This reagent forms a 1: 1 complex with HgBr3-that is slightly soluble in water and can be extracted with butyl acetate. The influence of the acidity, bromide ion concentration and foreign ions were investigated. Mercury can be determined in the range 1.5–15 ng ml–1. The stoicheiometry and apparent stability constant of the complex were determined. The method is applicable to the determination of mercury in sphalerites and organomercurials in cleaning solutions for contact lenses.

Chlorhexidine loss from simulated contact lens solutions stored in glass and plastic packages

Chlorhexidine loss from simulated contact lens solutions stored in glass and plastic packages

Complications of Preservatives in Contact Lens Solutions

ABSTRACT The addition of preservatives in contact lens solutions has been used as a means of killing bacteria or preventing their growth. With the widespread use of preservatives it has become increasingly evident that they have the ability of being adsorbed and absorbed by contact lenses. Consequently, the ocular tissues can be exposed to preservatives over a prolonged period of time. Since the 1970s practitioners have become aware of the adverse reactions resulting from the use of preservatives. The frequency of the complications attributed to the use of preservatives is difficult to ascertain, but most manufacturers and practitioners estimate it to be in the victinity of 5–10%. Preservatives have been shown to have a toxic effect on the cornea, causing disruption of cell structure and possible malfunction of epithelium, stroma and endothelium. In recent years preservatives, in particular thimerosal, have been recognized as having the ability to elicit allergic responses. This paper reviews the present literature on the complications of using preservatives. It concludes that much more research is needed in this area. Until the long term implications of preservatives in contact lens solutions are known, heat disinfection with non-preserved saline is a practical and safer alternative.

Reactions induced by the concurrent use of thimerosal and tetracycline.

We examined the reaction to thimerosal which occurred when patients were prescribed tetracyclines simultaneously. Nine patients were identified who had been using a 0.004% thimerosal-containing contact lens solution for over 6 months. All had developed varying degrees of ocular reaction (red eye, irritation, blepharitis) apparently as a result of taking tetracyclines concurrently. The reaction disappeared upon discontinuance of either the thimerosal or the tetracyclines. The hypothesis that the reaction was due to an interaction between thimerosal and tetracyclines was confirmed in rabbits.

Manual of Ophthalmic Terminology

This book is written by the authors of<i>The Ophthalmic Assistant</i>and is designed to acquaint allied health personnel with the basic meaning of ophthalmic terminology, including simplified drawings of anatomy, photographs of instruments, and some ocular pathology. The various chapter topics include the following: anatomy and surgical intervention, optics and refraction, contact lenses, spectacles, ocular disorders, ophthalmic tests and devices, and ophthalmic drugs. There are ten tables in the appendix. The introductions to the chapters give the Latin and Greek derivatives of ophthalmic terms, which might be of more interest to a scholar than a technician and are followed by a definition of the terms that are alphabetized. The appendices include tables of the following: abbreviations, metric conversions, contact lens solutions, a drug formulary listed under general actions, strengths of the medications and container size, estimations of percentage of visual loss, and conversions of spectacle power and contact lenses

Light-induced genetic toxicity of thimerosal and benzalkonium chloride in commercial contact lens solutions

Several commercial solutions used for daily care of contact lenses were tested for mutagenicity in 4 strains of Salmonella and for their ability to induce repairable DNA damage in the E. coli DNA polymerase A − assay. 5 of the 13 solutions tested were positive in the polymerase A − assay. These products demonstrated an increased level of genetic toxicity when the assay was conducted under conditions of illumination with visible light. Investigation of the genetic toxicity of some of their components, specifically the preservatives, indicated that thimerosal and benzalkonium chloride were capable of causing repairable DNA damage. Thimerosal was active only when the plates were incubated under conditions of illumination, and thus was light-induced. Benzalkonium chloride was active under conditions of dark incubation, and its genetic toxicity was enhanced when the plates were irradiated with visible light. These results were confirmed in a parallel experiment, in which cells were treated with the test agent and irradiated for a short period in liquid culture and viable cells then determined. None of the commercial products and none of the components tested, were mutagenic in the Salmonella assay.

The effects of ophthalmic preservatives on corneal epithelium of the rabbit: A scanning electron microscopical study

The cytotoxic effect on the corneal surface of rabbits of five preservatives used in contact lens solutions or eye cosmetics was investigated by scanning electron microscopy and light microscopy. The preservatives were tested in the concentrations normally used and a five times higher concentration. After local in vivo application of p-hydroxybenzoic acid ethyl ester (0.6%) or benzalkonium chloride (0.01%) for 30 min, only the upper or outer cell layer of the corneal epithelium was affected; moderate loss of microvilli and focal desquamation of the superficial cells were seen. Chlorhexidine (0.1%) and formaldehyde (0.05%) caused a complete loss of the top cell layer; the second cell layer showed loss of microvilli. Hexachlorophene (0.3%) had the most pronounced effects: a nearly complete loss of the two top layers, while the third cell layer was still intact. Fivefold higher concentrations of the same preservatives caused even more serious damages: all agents showed deleterious effects on at least the two upper layers of cells whereas hexachlorophene had cytotoxic effects on several and occasionally all cell layers constituting the corneal epithelium.

Chemical Components of Contact Lens Solutions

With the myriad of contact lens solutions on the market today, it becomes difficult to choose the appro­priate contact lens system for the patient. Three major factors to be considered in the choice are safety, efficacy and cost. To determine the efficacy of a solution, an understanding of its components is required. Unfortunately, certain manufacturers are unwilling to dis­close their formulations. The au­thors encourage practitioners not to use such solutions. Most manufac­turers, however, do list the active ingredients.

Preservation of cosmetics and contact lens solutions

Preservation of cosmetics and contact lens solutions

The compatibility of benzalkoniumchloride with a CAB lens material

The compatibility of benzalkonium chloride, adisinfectant and preservative used in hard contact lens solutions, with a commercial CAB lens material has been assessed by determining the level of uptake from isotonic buffered solution at pH 7.0, a commercial soaking solution and a commercial wetting solution at temperatures of 15° and 30°. The results, using polymer materials in both powdered form and as lenses showed, that in all studies, the level of interaction of benzalkonium chloride was less with the CAB material than with poly-methyl methacrylate. The average uptake from the commercial soaking solution was 7.6μg per lens by CAB lenses compared to 10μg per lens for PMMA lenses whilst for the wetting solution the corresponding figures were 1.5μg and 6.8μg respectively. A parallel study involving microscopic examination of lens surfaces and determination of lens parameters showed no physical changes in the CAB lenses after two months storage at 34° in the soaking formulation to which 0.2% benzalkonium chloride had been added. It is concluded that, in contrast to statements in the literature (1, 2), benzalkonium chloride is not incompatible with at least the commercial CAB material used in this study.

Application of iron(III)--hydroxamic acid complexes in the spectrophotometric determination of poly(vinyl alcohol) in pharmaceutical preparations.

A spectrophotometric method is presented for the quantitative determination of poly(vinyl alcohol)(PVA) in contact lens solutions and eye-drops. The method is simple and requires no sample pre-treatment. The procedure is based on the measurement of the absorbance after iron(III)-hydroxamic acid reaction with PVA. The method is useful in quality control and as a screening procedure for solutions considered as PVA-containing mixtures of an unknown type. As the absorbance is dependent of the content of residual acetate groups in the PVA, the type and ester value can be determined.

Complications Associated with Contact Lens Solutions

The complications that have been seen when hydrophilic lenses are cared for by chemical decontamination are reviewed. The findings that help to differentiate lens-induced changes from chemical-care-produced changes are presented. Incompatibilities between care methods are illustrated. The complications are discussed in terms of changes produced in the cornea, conjunctiva, flora of the cul-de-sac, and lens.

Colorimetric Determination of Poly(N-Vinyl-2-Pyrrolidone) in Contact Lens Solutions

A rapid colorimetric method is presented for the quantitative determination of poly(N-vinyl-2-pyrrolidone) in contact lens solutions. The method is simple, requires no sample pretreatment, and uses only a small volume of sample. The procedure is based on the measurement of the net absorbance of a poly(N-vinyl-2-pyrrolidone)- Congo red complex at 545 nm. An accuracy of greater than +/- 4% was obtained for the concetnration ranges usually found in contact lens solutions with a minimum detection level of 10 ppm. The method is useful as a screening procedure for solutions of unknown composition and as a quality assurance procedure for routine determinations.

The properties of commercial contact lens wetting solutions

Dr. B. J. Tighe, who is Senior Lecturer in Polymer Science, in the Department of Chemistry at the University of Aston in Birmingham, has been a member of the DHSS working parties on contact lens solutions and lens materials. He has an active research group who have been working for several years on various aspects of the design of polymers for biomedical applications such as contact lenses, artifical liver support systems and dialysis membranes.

Antimicrobial agents as preservatives in pharmaceutical and cosmetic products. Agents as preservatives in eye-drops and contact lens solutions.

Antimicrobial agents as preservatives in pharmaceutical and cosmetic products. Agents as preservatives in eye-drops and contact lens solutions.

Response to the Report ‘Influence of Soft Contact Lens Solutions on Rabbit Cornea’ by Dreifus and Wobmann

Objections are raised to the interpretation by Dreifus and Wobmann of their findings regarding cold disinfecting solutions used during the wearing of soft hydrophilic contact lenses by rabbits. Their

Measurement of Preservative Binding with SOFLENS® (polymacon) Contact Lens*

A study was initiated to determine which preservatives, frequently used in ophthalmic solutions, bind with SOFLENS® (polymacon) Contact Lenses. Zone of inhibition assays were employed to detect and measure preservative binding. Lenses soaked in preservative solutions at concentrations normally used in ophthalmic preparations were subjected to various extraction techniques. These lenses were then placed on seeded agar plates of Staphylococcus aureus or Trichophyton mentagrophytes, incubated and examined for the appearance of zones of inhibition. The amount of extraction required to prevent zone formation was interpreted as a measure of preservative binding. Results showed that: (1) thimerosal, thimerosal with disodium edetate, and propylparaben bind weakly; (2) phenyl‐mercuric acetate and phenylmercuric nitrate bind moderately; and (3) chlorhexidine gluco‐nate, benzalkonium chloride, and an alkyl triethanol ammonium chloride compound bind strongly to the lens material.Other studies included in this paper suggested that formulation components and the methods employed for the preparation of commercially available soft contact lens solutions may alter the binding characteristics of the preservative components.

Contact Lens Solutions: Too High A Standard Aimed at?*

Future legislation concerning contract lens solutions is likely to require that they have a certain minimum antibacterial activity and, therefore, a minimum preservative concentration. But using present antibacterial agents, solutions could not be formulated to meet the possible requirements since the necessary concentration of preservative would cause irritancy to wearers of soft contact lenses. However, is such high antibacterial efficiency necessary? That was one of the points raised by Dr. D. J. G. Davies (school of pharmacy and pharmacology, University of Bath) at an evening meeting of the Pharmaceutical Society held in London on January 14. Dr. Davies was speaking on the problems associated with the use of contact lens solutions. Dr. Davies's talk is summarised below.

Contact Lens Practice

Part 1 History: origin of the contact lens, Anthony Sabbell. Part 2 Material technology: chemical composition & properties, Miguel Refojo oxygen transport through contact lenses, William Benjamin mechanical properties, Ronald E. Stephenson. Part 3 Contact lens design technology: contact lens design, Michel Guillon and William Sammons soft contact lens kinetics, Yoshizo Kikkawa contact lens optics, Colin Fowler quality assurance and quality control for volume lens manufacturing, Stewart Gibson quality control of rigid lenses in clinical practice, Richard Pearson the verification of soft lenses in clinical practice, Michael Port manufacturing standards, Michael Sheridan. Part 4 Anatomical & physiological factors: microscopic anatomy and ultra structure of the cornea, conjunctiva and lids, Ramesh Tripathi, et al innervation of the anterior segment, Gordon Ruskell corenal physiology & biophysics, Stephen Kwok biochemical aspects of the cornea, Barry Masters. Part 5 Clinical techniques: keratometry & specialist optical instrumentation, Ronald Rabbetts photokeratoscopy & corneal topography, Arthur Ho and Michel Guillon biomicroscopy, Steve Zantos and Ian Cox pachometry - clinical & scientific applications, Tailoi Chan and David Pye aesthesiometry, Michel Millodot the role of tears in contact lens performance and its measurement, Jean-Pierre Guillon oxygen consumption & measurements, Richard Hill. Part 6 Practical routine: indications and contraindications for contact lens wear, Barry Weissman preliminary examination patient selection, Barry Weissman contact lens care systems and solutions used by the practitioner, Fiona Stapleton & Judith Stechler symptomology and aftercare, Joshua Joshephson, et al. Part 7 Fitting techniques: basic contact lens fitting, Michel Guillon fitting the astigmatic patient with rigid contact lenses, Theodore Grosvenor toric hydrogel contact lenses, Nigel Burnett Hodd and Joshua Josephson tinted hydrogel contact lenses, Richard Weisbarth the scleral regid lens - optical and therapeutic applications, Montague Ruben gas permeable scleral contact lenses, Oliver Schein, et al presyopia and influence of ageing on the prescription of contact lenses, William Benjamin and Irving Borish contact lenses for children, David Taylor and Judith Morris. Part 8 Abnormal and therapeutic fitting: correction of irregular astigmatism with contact lenses, Montague Ruben contact lens fitting post refractive surgery, Christine Astin orthokeratology, Leo Carney therapeutic soft contact lenses, Thomas John, et al. (Part contents.)