The CLAO Journal

Volume 25, Number 1 -- January 1999

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Copyright 1998 Contact Lens Association of Ophthalmologists, Inc. All rights reserved.

Cytotoxicity Evaluation of Multipurpose Contact Lens Solutions Using an In Vitro Test Battery X. T. Pham, PhD; J. W. Huff, PhD Purpose: Many in vitro alternatives to eye irritation testing are not mechanism-specific and do not employ ocular cell lines. We have developed an effective and reliable test battery that reveals toxicity mechanisms of contact lens solutions on cell metabolism and proliferation. Methods: Cytotoxicity endpoints were quantified using bovine corneal epithelial cultures in 96-well microplates. A kenacid blue assay provided information on total cell protein, while lactate production and alamarBlue assays served as indicators of aerobic/anaerobic metabolism and redox state of cells grown in serum-free Dulbecco's modified Eagle's/Ham's F12 medium (DMEM/F12). Concentrations (% v/v) causing 10&SHY;90% inhibition of the control assay responses were used for correlations with in vivo data. Results: Cytotoxicities of contact lens solutions correlated better with irritant symptoms than with corneal staining, and were ranked as follows: Lens Plus << Opti-Free < ContaClair < ReNu. Lens Plus was not toxic to cell glycolysis, respiration, and proliferation for up to 20% v/v. However, the multi-purpose solutions inhibited these endpoints in a concentration-dependent manner. Opti-Free and ReNu, containing Dymed and Polyquad® (ammonium surfactants), showed non-specific cell inhibition. The lactate production assay had a flatter log concentration-response curve than the other two assays. Conclusions: The proposed biochemically-based test battery using the target corneal epithelium has the potential to be a simple and effective method for screening and defining toxicity profiles of contact lens care solutions. The model can be applicable to small- or large-scale testing programs and research and development of new ocular products. Back to Table of Contents

Clinical Assessment of the Piggyback Bifocal Contact Lens System Lisa J. T. Vredevoogd, MD; Gilbert Litteral, FCLSA; John R. Bierly, MD; Ghassan Cordahi, MD On-Line Dialogue: Click the mailbox to submit questions or comments on this article. Please include article title or author as well as your name and postal address. Purpose: We performed a qualitative and quantitative assessment of contact lens performance at 1 and 6 months among 24 patients enrolled in the Piggyback Bifocal Contact Lens Study. Methods: We fit 24 presbyopic patients with the Piggyback Bifocal Contact Lens System (i.e., a plano soft lens with a 9.4 mm cutout portion on which a bifocal RGP lens rides or "piggybacks"). Patients were evaluated prior to inclusion in the study and then at one month and six months after obtaining their lenses. Evaluations included slit lamp examination, evaluation of visual acuity at near and distance, and subjective rating of the patients' comfort. Results: At one month, 61% of patients had Snellen acuities of 20/30 or better, 79% had near acuities of J2 or better, and 60% rated their comfort as good or very good. At six months, 100% of patients had Snellen acuities of 20/30 or better, 90% had near acuities of J2 or better, and 86% of patients rated their comfort as good or better. Twelve patients did not complete the study due to their decision to drop the study. Conclusions: The Piggyback Bifocal Contact Lens System is a well-tolerated, satisfactory means of optical correction for the motivated presbyope. Back to Table of Contents

Omafilcon A (Proclear) Soft Contact Lenses in a Dry Eye Population Michael A. Lemp, MD; Barbara Caffery, OD, FAAO; Kenneth Lebow, OD, FAAO; Richard Lembach, MD; Juliana Park, MD; Gary Foulks, MD; Brenda Hall, BSc, PhD; Roderick Bowers, PhD; Shirley McGarvey, BS, MBA Graeme Young, BSc, MPhil, FCOptom, DCLP, FAAO On-Line Dialogue: Click the mailbox to submit questions or comments on this article. Please include article title or author as well as your name and postal address. Purpose: We conducted a 3-month, randomized, comparative cross-over study to evaluate the clinical performance of lenses manufactured from omafilcon A on subjects with signs and symptoms of dry eye. The subjects' own daily wear soft lenses were used as controls. Methods: Seventy-six subjects with objective evidence of dry eye, as defined in the NEI/Industry Workshop Report 1995, were fit with either the omafilcon A lenses (Proclear) or new control lenses. Subjects wore the lenses for 6 weeks and then crossed over to bilateral wear of the other lenses for an additional 6 weeks. During each part of the study, we examined subjects at 1 week, 1 month, and 6 weeks. Signs and symptoms of dry eye were evaluated, and on-eye dehydration of the lens was assessed. Results: When the subjects were wearing the omafilcon A lenses, there was a statistically significant improvement in a number of subjective parameters including comfort, dryness, frequency of eye irritation, and frequency of burning. We found significantly less on-eye dehydration of the lens and luorescein corneal staining with the omafilcon A lenses. Conclusions: This study indicated that the daily wear of omafilcon A lenses provided better comfort, fewer symptoms, less on-eye dehydration, and less fluorescein corneal staining than other soft daily wear contact lenses in subjects with mild to moderate dry eye. Back to Table of Contents

Comparison of Contrast Sensitivity in Different Soft Contact Lenses and Spectacles Brian S. Boxer Wachler, MD; Cathy L. Phillips, OD; David J. Schanzlin, MD; Ronald R. Krueger, MD Purpose: To compare the visual performance of soft contact lenses and spectacles. Methods: Twenty eyes of ten patients were examined. Each patient was fit with Acuvue, Cibasoft, and Biomedics contact lenses in random order. LogMar visual acuity and contrast sensitivity using the VectorVision CSV-1000 were measured. Results: There was no significant difference in visual acuity between any contact lenses (P=.15). Contrast sensitivity at 12 cycles/degree was significantly lower for the Cibasoft lens compared to spectacles (P=.04). There was no significant difference between spectacles and contact lenses for remaining spatial frequencies (P=.07­.35). Conclusions: Visual acuity appears to be an insensitive method for evaluating soft contact lenses. The lathe-cut manufacturing process may be responsible for reduced visual function compared to cast-molded lenses. Further study in this area is needed. Back to Table of Contents

Comparative Antimicrobial Efficacy of Multi-Purpose Lens Care Solutions Using the FDA's Revised Guidance Document for Industry: Stand-Alone Primary Criteria Andrea M. Lever, BA; Michael J. Miller, PhD Purpose: We evaluated six single-bottle, multi-purpose lens care solutions and a two component lens care system for disinfection efficacy according to the stand-alone primary criteria within the recently published U.S. Food and Drug Administration (FDA) Guidelines. Methods: One-tenth mL of 1 x 108 colony forming units (CFU)/mL of bacterial and fungal challenge organisms was added to each test solution. Following a specified period (e.g., each manufacturer's labeled minimum disinfection time), aliquots of inoculated test solution were neutralized and plated on validated recovery media. After incubation the number of viable microorganisms were enumerated and mean log reductions determined. Results: ReNu and ReNu MultiPlus met the FDA's acceptance criteria for stand-alone disinfectants against all challenge organisms: Staphylococcus aureus, Serratia marcescens, Pseudomonas aeruginosa, Candida albicans, and Fusarium solani. Opti-Free Express failed to meet the FDA's stand-alone disinfectant acceptance criteria for S. aureus, S. marcescens and C. albicans and Opti-Free Express with Opti-Free Supraclens failed to meet the acceptance criteria for either S. aureus and C. albicans. Opti-One failed to meet the FDA's stand-alone disinfectant acceptance criteria for C. albicans and F. solani. Both Complete and Solo-Care failed to meet the FDA's acceptance criteria for C. albicans. Conclusions: This evaluation provides a direct comparison of antimicrobial activity (based on stand-alone criteria) for commercially available multi-purpose lens care solutions at their labeled minimum disinfection times. The results of this study should be considered when selecting appropriate lens care systems for patients. Back to Table of Contents

Assessment of Corneal Decompensation in Eyes Having Undergone Molteno Shunt Procedures Compared to Eyes Having Undergone Trabeculectomy Jean N. Zalloum, MD; Richard M. Ahuja, MD; Dong Shin, MD, PhD; Jayne S. Weiss, MD Purpose: To compare the incidence of corneal decompensation after Molteno shunt to trabeculectomy. Methods: We conducted a retrospective analysis of the corneal status of 55 patients with primary open angle glaucoma. We compared 24 eyes of 24 patients who underwent Molteno tube shunt placement (Group 1) to fifteen eyes of 14 patients with multiple surgical procedures, including a trabeculectomy (Group 2). We also compared Group 1 to 28 eyes of 17 patients who underwent only one trabeculectomy (Group 3). Results: The three groups were similar with respect to age, sex, and intraocular pressure (IOP). The average follow-up time from the last surgery in Group 1 was 17.9 months (1­90 months), 22.4 months (2­63 months) in Group 2, and 19.6 months (1­37 months) in Group 3. The average number of surgeries was 3.0 (1­4) in Group 1 and 2.53 (1­4) in Group 2. The surgeries included trabeculectomy, cataract extraction, combined procedures, penetrating keratoplasty, pars plana vitrectomy, and scleral buckle. The incidence of corneal edema was 50% (12/24)in Group 1, 6.7% (1/15) in Group 2, and 0% in Group 3 (0/28). The average time to corneal decompensation was 21 months in Group 1 (1­120 months) and 15 months in Group 2. Conclusion: Patients undergoing Molteno shunt placement have a higher rate of corneal decompensation compared to patients undergoing trabeculectomy. Back to Table of Contents

Editorial A Look Back As we approach the dawn of the next century it behooves us to stop and reflect on the monumental developments that have occurred in the field of vision correction. This is especially true in light of the recent death of Dr. Otto Wichterle (see In Memoriam on page 4). It was only 50 years ago that the first patent for a corneal contact lens was issued to Kevin Tuohy; and only 42 years ago that the first soft HEMA contact lens was placed on a human eye. In 1961, Dr. Wichterle's proposal for the development of a spin-casting technique for manufacturing contact lenses was rejected. Continuing his research in his home, Otto Wichterle developed the spin-casting technique and produced over 5,000 lenses between January and April of 1962-a number that can be produced in one day with current contact lens manufacturing methodology. From these humble origins, Bausch & Lomb introduced the soft contact lens in 1972. A series of "alphabet lenses" soon became our armamentarium in fitting contact lenses. Over the next few years other companies became interested in developing and manufacturing contact lenses. A variety of designs and polymers became available, increasing the contact lens options for our patients. In the last 5 to 10 years contact lenses to correct high degrees of myopia, hyperopia, and astigmatism have become available. High Dk RGP materials have also been developed, improving the corneal response to rigid contact lenses. High Dk soft polymers are being investigated that may make extended or continuous wear soft contact lenses safer. In addition, bifocal contact lenses are available to correct presbyopia. Today almost anyone who wants to wear contact lenses can be fit successfully. In the 1980s we embraced the concept of the "marathon" contact lens. We employed every conceivable technique to keep the contact lens "clean" so the patient would not have to purchase a new lens. The 1990s ushered in the concept that it was preferable for our patients to replace their lenses at more frequent intervals than once a year. The frequent replacement of contact lenses was shown to be beneficial both to the patient and the practitioner. The introduction of the daily disposable contact lenses-the ultimate frequent replacement contact lens-has been helpful in allowing many individuals who were contact lens "drop outs" to return to contact lenses. In addition, it has significantly lowered the incidence of problems and complications associated with contact lens wear. If this was the extent of the advances in refractive eyecare, we could look back and marvel at these developments. However, the development of refractive surgery in the last 20 years adds another dimension to this expanding field. Excimer laser technology was first developed in 1976; the first patent for its use on the cornea was issued in 1983. The first "normal" sighted eye was treated with the excimer laser in 1987. Today laser refractive surgery, both PRK and LASIK, is able to correct a wide range of refractive errors. In addition, intrastromal corneal rings, phakic intraocular lenses (or phakic refractive lenses), and refractive cataract surgery are being investigated as alternative methods of vision correction. These advances have given the practitioner many choices for correcting their patients' vision. With these advances comes the responsibility of being in a position to offer our patients the best modality for their individual visual needs. This requires the education of the practitioner as to the risk and benefits of each procedure and modality. Practitioners must then educate their patients. The 1999 CLAO Annual Meeting offers the opportunity to gain important pearls on all forms of vision correction. To those of you who have joined us in Las Vegas-Welcome! For those who could not make it, I hope to see you in the year 2000. Finally, if you would like to contribute to the next century of research in vision correction, please see our Call for Papers ad on page 18. Peter C. Donshik, MD Editor-in-Chief The CLAO Journal Back to Table of Contents

E-Mail: CLAOJrnl@aol.com

Copyright 1998 Contact Lens Association of Ophthalmologists, Inc. All rights reserved.