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PubMed1996

Indications and complications of therapeutic disposable Acuvue contact lenses.

PURPOSE: Although therapeutic hydrogel contact lenses have been used for many years, there have been few reports on the therapeutic use of disposable lenses. We evaluated lens fit, duration of wear, efficacy of therapy, complications, and concurrent treatment in patients with corneal or anterior segment problems who were managed with Acuvue contact lenses for therapeutic purposes. METHODS: We managed 38 patients with corneal or anterior segment disease during 1992-1994. The duration of lens wear ranged from several days to 12 months. Six patients were fit for mechanical reasons, six were fit for symptomatic relief, and 26 were fit as an adjunct to healing. Technical failures included lenses with inadequate movement and lenses that fell out of the eye. Therapeutic failures occurred when lens use did not help resolve the anterior segment problem. RESULTS: Seventy-one percent of patients were fit successfully, and 66% of patients were therapeutic successes. Complications with contact lens fitting included lens loss, discomfort, corneal ulceration, and tight lens syndrome. CONCLUSIONS: Although we found some difficulty in lens fitting, Acuvue lenses may provide a useful, disposable, and less expensive alternative to the traditional bandage contact lens.

Adolescent↗

PubMed1979

[Contact lenses: indications and limits].

Contact lens wear may be indicated for cosmetic, professional, optical or therapeutic reasons. For each of these indications the arguments are given, why and when contact lenses are better than spectacle correction and which possibilities there are. Contact lens wear is contraindicated in certain eye diseases and in the case of problems of handling and hygiene. The author's preferences concerning the different contact lens materials are summarized briefly.

Aphakia↗

PubMed1987

A comparison between the measured and the desirable quality of hydrogel extended wear contact lenses.

Eighty-two hydrogel extended wear contact lenses (EWCL) from four brands were tested for overall quality and variations in specified parameters. Two of the EWCL brands were approved by the United States Food and Drug Administration (FDA) for wear by the public, while two of the brands were uninvestigated. In addition, the packaging solution was examined for osmolarity and pH. All brands were delivered with solutions that had estimated means of pH and osmolarity departing from what may be considered ideal physiologically. The EWCLs all had a consistent power and an acceptable thickness reproducibility. One of the FDA approved brands, demonstrated diameter variations of a magnitude that may produce an unpredictability in the lens fit. Several lenses of one brand suffered from edge quality deficiencies. Although the FDA clinical trial is designed to control the clinical performance of contact lenses prior to the market entry, the results of the present investigation indicate that an authority independent of the manufacturer should regularly sample the lens quality. It is for this purpose imperative that standards for contact lenses are established.

Contact Lenses, Extended-Wear↗

PubMed1985

The flight acceptability of soft contact lenses: an environmental trial.

Seventeen officer aircrew, wearing soft contact lenses, were subjected to adverse conditions likely to be encountered in military aviation. The stresses included hypoxia, rapid decompression, pressure breathing, vibration, climatic extremes, G forces, and the prolonged wearing of an aircrew respirator. Their visual performance wearing contact lenses under stress did not differ significantly from the control values; either when wearing corrective flying spectacles or contact lenses when not under stress. It is considered that from the environmental standpoint soft contact lenses are suitable for aircrew. As contact lenses may not be tolerated by all, and may cause undesirable side-effects in some, their use should be restricted to the aircrew to whom they offer the maximum advantages. The group most likely to benefit are young, well motivated myopes flying fast jets.

Aerospace Medicine↗

PubMed2005

Ocular release of timolol from molecularly imprinted soft contact lenses.

The aim of this study was to evaluate "in vivo" the usefulness of molecular imprinting technology to obtain therapeutic soft contact lenses capable of prolonging the permanence of timolol in the precorneal area, compared to conventional contact lenses and eyedrops. Soft contact lenses (diameter 14 mm, center thickness 0.08 mm) consisted of N,N-diethylacrylamide (DEAA; main component of the matrix), methacrylic acid (MAA; functional monomer) and ethylene glycol dimethacrylate (EGDMA; cross-linker) were prepared by the conventional methodology (non-imprinted) or by applying a molecular imprinting technique using timolol as the template (imprinted ones). After washing and reloading, timolol release studies carried out in rabbits showed that the soft contact lenses made by the molecular imprinting method (34 microg dose) provided measurable timolol concentrations in the tear fluid for 2.0- and 3.0-fold longer than the non-imprinted contact lenses (21 microg dose) and eyedrops (doses of 34 and 125 microg), respectively. Furthermore, the area under the timolol concentration-time curve (AUC) was 3.3- and 8.7-fold greater for imprinted contact lenses than non-imprinted contact lenses and eyedrops, respectively. The timolol concentration of the eyedrops did not affect the precorneal residence time of drug significantly. On the other hand, timolol loading capacity of the contact lenses was improved by the molecular imprinting method; the sustaining of the drug levels in the tear fluid being proportional to the loading capacity of the contact lenses. These results indicate that imprinted soft contact lenses are promising drug devices able to provide greater and more sustained drug concentrations in tear fluid with lower doses than conventional eyedrops.

Absorption↗

PubMed1978

Contact lenses. Separating fact from fancy.

Contact lenses are a valuable addition to the methods of visual correction and can be used successfully in most cases if patients are properly fitted, instructed, and supervised. The majority of patients can be fitted with conventional hard lenses; soft lenses are preferred in special situations. The most important consideration with either type of lens is proper fitting, which is essential for preservation of normal corneal morphology and physiology.

Child↗

PubMed1989

Actual wearing time vs. possession time of contact lenses.

Sixty-two subjects who had never worn contact lenses were fitted with various rigid gas permeable (RGP) contact lenses. Contact lens wearing logs kept by the subjects indicated up to an 8-fold difference in total on-the-eye wearing hours among the subject population. Average daily wearing time for the group during the 7 to 12 month interval was 9.42 h/day. These findings show that persons who have had rigid lenses in their possession for 1 year have widely varied wearing times, and that "time from dispensing" does not accurately reflect patient lens use. Wearing schedule "gaps" are frequently due to broken or lost lenses, and perceived lens comfort seems to affect total wearing time significantly.

Adolescent↗

PubMed1987

The effect of enzymatic contact lens cleaning on adherence of Pseudomonas aeruginosa to soft contact lenses.

Previous studies have demonstrated that Pseudomonas aeruginosa adheres more readily to soft contact lenses with a mucin coating than to unworn contact lenses. The mucin coatings that develop on soft contact lenses may, therefore, play a significant role in the pathogenesis of contact lens-associated Pseudomonas corneal ulceration. We tested the ability of a variety of enzymatic contact lens cleaners and other enzyme solutions to decrease the adherence of Pseudomonas to mucin-coated soft contact lenses. Of the commercially available solutions that were tested, cleaning with Optizyme and Extenzyme significantly reduced the adherence of Pseudomonas to the lenses, whereas cleaning with the Softmate Weekly Cleaning System had no effect. Optizyme and Extenzyme were as effective as a 10% solution of acetylcysteine and more effective than a 0.25% trypsin solution. Neuraminidase at pH 5 was the most effective solution at reducing the adherence of Pseudomonas to the lenses, supporting the finding that sialic acid is a specific receptor for Pseudomonas aeruginosa. Soft contact lenses should be cleaned frequently with an effective enzymatic cleaner to reduce the likelihood of Pseudomonas adhering to the lens and thereby reduce the incidence of Pseudomonas corneal ulceration in soft contact lens wearers.

Acetylcysteine↗

PubMed1998

Influence of special-effect contact lenses (Crazy Lenses) on visual function.

PURPOSE: Special-effect contact lenses (opaque, tinted soft contact lenses that incorporate decorative images such as "cateyes," stars, or hearts to alter eye color and structure) have become increasingly popular. The purpose of this study was to investigate whether such lenses impair visual function. METHODS: A clear soft contact lens and a special-effect soft contact lens (Crazy lens,) were fit in changing sequence in nine healthy subjects. The parameters studied included: visual acuity, contrast sensitivity (with and without glare), visual field, and mesopic vision (with and without glare). RESULTS: The following parameters displayed a statistically significant difference (P < 0.05). Visual acuity was decreased to 0.9 +/- 0.23 in the Crazy lens group as compared with 1.2 +/- 0.13 in the clear lens group. Goldmann visual field displayed a significant constriction of the isopters: III/4, I/4, and I/3. Mesopic vision without glare was reduced from 1:2.5 to 1:7.4. Contrast sensitivity was significantly reduced in a photopic condition with and without glare and in a scotopic condition without glare. Furthermore, the special-effect lenses were associated with a decrease in lens wearing comfort. CONCLUSIONS: Special-effect contact lenses were associated with a reduction of many visual functions, including visual acuity and contrast sensitivity. For some wearers this may interfere with activities where excellent vision is crucial, such as driving a car.

Adult↗

PubMed1998

First- and third-order optical theory of gradient index materials, with application to contact lenses.

PURPOSE: To investigate the feasibility of using gradient index media in contact lenses, we developed simple methods which we used to derive the power and aberrations associated with the contact lenses. METHODS: In one method, we assume that the height of a ray does not change as it passes through the lens. We describe a second method in which the ray is assumed to follow a parabolic path as it passes through the lens. We use sophisticated third-order theory and finite raytracing for comparison with these methods. RESULTS: The methods are compared for contact lenses with parabolic radial gradient index media. Without the gradient index, these lenses would have zero power. The formula for power which assumes no change in ray height gives errors of approximally 0.8 and 1.5% for lenses of thicknesses 0.18 and 0.36 mm. However, the formula for third-order spherical aberration which uses the same assumption gives poor estimations. The method for calculating power using the parabolic ray path is very accurate. The sophisticated third-order aberration theory was reasonably accurate out to 2.5 mm ray height. The contact lenses with the gradient index media have much smaller aberration in air than do conventional contact lenses of the same powers, with the sign of the aberration being reversed. CONCLUSIONS: Our simple procedures give good estimations of powers of contact lenses with gradient index media. The approximate method, which assumes that the height of a ray does not change as it passes through the lens, should not be used for finding the spherical aberration of such a lens. Contact lenses with gradient index media have potential for minimizing spherical aberration.

Contact Lenses↗

PubMed1998

Accelerated study on lysozyme deposition on poly(HEMA) contact lenses.

A technique was developed to accelerate lysozyme deposition on poly(HEMA) contact lenses and measure the amounts of the deposited lysozyme. This technique was for evaluation of bendazac lysine solution, a contact lens cleaning and wetting solution. Effect of temperature on lysozyme deposition on poly(HEMA) contact lenses was examined. Five temperatures ranging from 25 degrees C to 90 degrees C were chosen to examine the temperature effect. The amounts of lysozyme deposited on poly(HEMA) contact lenses at 25 C and 60 C were 0.27 microg/lens and 0.61 microg/lens, respectively. The amount increased sharply to 23 microg/lens at 70 degrees C with the maximum of 31 microg/lens at 90 degrees C. Kinetics of lysozyme deposition on poly(HEMA) contact lenses was examined at 80 degrees C. Lysozyme deposition increased sharply during the first 2 h and reached a plateau after 2 h. Effectiveness of various cleaning procedures was examined using bendazac lysine solution. When the contact lenses were washed without rubbing with fingers, the bendazac lysine reduced the amount of deposited lysozyme by more than 40% from 18.3 microg/lens to 10.6 microg/lens. The effect of bendazac lysine was most prominent when the contact lenses were shaken during storage in the presence of lysozyme in solution. If the contact lenses were cleaned by rubbing with fingers, the effect of bendazac lysine solution on the prevention of lysozyme deposition was negligible.

Biocompatible Materials↗

PubMed1993

Deposition of ciprofloxacin, prednisolone phosphate, and prednisolone acetate in SeeQuence disposable contact lenses.

We noted opaque deposits in SeeQuence disposable contact lenses in three patients with persistent epithelial defects who were being treated with topical ciprofloxacin and prednisolone acetate. In each patient, the contact lenses with deposits were removed and replaced. High performance liquid chromatography analysis revealed the deposits to be precipitates of ciprofloxacin and prednisolone acetate. We incubated new SeeQuence disposable contact lenses in ciprofloxacin, prednisolone phosphate, and prednisolone acetate alone and in combination. Precipitates did form when ciprofloxacin was combined with either prednisolone acetate or prednisolone phosphate. We recommend removal and replacement of contact lenses should these deposits develop to prevent the possibility of corneal toxicity.

Aged↗

PubMed1986

Corneal ulcers associated with daily-wear and extended-wear contact lenses.

Over a 21-month period, we treated corneal ulcers in 11 patients using daily-wear contact lenses and 29 patients using extended-wear contact lenses. Since more patients use daily-wear than extended-wear lenses, this suggests that patients using extended-wear lenses are at greater risk for the development of corneal ulcers. Positive bacterial cultures were obtained from the corneal scrapings of nine of 11 patients using daily-wear lenses and 20 of 29 patients using extended-wear lenses. In the daily-wear group, all 11 patients failed to exercise satisfactory care in using and disinfecting their contact lenses: three did not wash their hands before manipulating the contact lenses, eight wore them overnight, two did not use any disinfecting system, and four had contaminated contact lens cases, solutions, or drops. In the extended-wear group, 17 patients failed to exercise satisfactory care in using and disinfecting their contact lenses: 12 had contaminated contact lens care systems, two did not use any disinfection system, five reported not washing their hands before contact lens manipulation, and two disinfected their contact lenses at intervals of more than a month. We were unable to identify any defect in the way 12 patients took care of their extended-wear lenses, suggesting that there may be a problem with these contact lenses even when care is satisfactory.

Adult↗

PubMedDate not supplied

[Ametropia correction with bifocal contact lenses].

Indications for the prescription of bifocal contact lenses have been defined, the technology of making such lenses of various designs developed, and specific features of the choice of these lenses analysed. The authors discuss the tentative choice of lenses, tentative and regular wearing of the lenses made at the optic mechanic laboratory of the institute. The results of correction of ametropia combined with presbiopia by bifocal and multifocal contact lenses are presented. Segmented and concentric (soft and rigid) bifocal contact lenses were employed; the authors come to a conclusion on the good prospects for the use of concentric lenses.

Contact Lenses↗

PubMed1983

Contact lenses for laser applications.

Contact lenses for anterior and posterior segment laser applications are described. Commercially available lenses are classified according to design, application, manufacturer and cost.

Contact Lenses↗

PubMed1993

Soft opaque contact lenses in binocular vision problems.

Soft opaque contact lenses may be useful in certain recalcitrant vision problems. When the full central area is opaque, contact lenses eliminate the visual image, provide acceptable cosmesis, and may be useful in cases of intractable diplopia as well as in the treatment of amblyopia. Artificial iris contact lenses eliminate para-axial rays in monocular diplopia, aniridia, and albinism.

Albinism, Oculocutaneous↗

PubMed1997

Contact lenses and corneal shields.

This article reviews literature regarding contact lenses and corneal shields published between February 1996 and January 1997 that will help the ophthalmologist to better understand some of the clinical effects of contact lenses and corneal shields. Progress has been made in understanding the interaction between contact lenses and the eye, and this may improve fitting. However, fitting presbyopic patients with contact lenses still remains a challenge. There is new insight in the pathomechanism of serious corneal infections caused by Acanthamoeba species and Pseudomonas aeruginosa, which may lead to decreases in these complications. Furthermore, in the era of different wear modalities and replacement schedules and the advent of daily disposable lenses, an update of contact lens terminology is provided.

Animals↗

PubMed1990

[Contact lenses and their problems].

Contact lenses cause many changes in the anterior segment of the eye, mainly in the cornea. The long-term effects on the corneal epithelium, stroma and endothelium are discussed, as are the more acute complications commonly seen in patients. Future trends in the contact lens field are also dealt with briefly.

Contact Lenses↗