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At least 109 records · Page 6Linked to original sources
PubMed1989

The incidence of ulcerative keratitis among users of daily-wear and extended-wear soft contact lenses.

The wearing of contact lenses has increased dramatically in the past decade; over 4 million people in the United States now use extended-wear soft contact lenses, and 9 million use daily-wear soft contact lenses. Numerous reports have caused concern that the use of soft contact lenses, especially extended-wear lenses, may result in a substantial risk of ulcerative keratitis. To examine this issue, we conducted a prospective study in five New England states to estimate the incidence of ulcerative keratitis among those who use cosmetic extended-wear and daily-wear soft contact lenses. To obtain the numerator for each estimate of incidence, we surveyed all practicing ophthalmologists in the study area to identify all new cases diagnosed over a four-month period. To provide the denominator, we conducted a survey of 4178 households to estimate the number of persons who wore each type of soft contact lens. The annualized incidence of ulcerative keratitis was estimated to be 20.9 per 10,000 persons using extended-wear soft contact lenses for cosmetic purposes and 4.1 per 10,000 persons using daily-wear soft contact lenses for cosmetic purposes (P less than 0.00001).

Adolescent↗
PubMed1986

Theoretical optics of toric hydrogel contact lenses.

Toric hydrogel contact lenses are used when spherical lenses prove inadequate at correcting refractive error due to astigmatism. A model of hydrogel contact lens flexure effects allows theoretical investigation of the in situ optical power of toric soft contact lenses. Total meridional power is believed to be the sum of meridional lens power and entrapped tear layer power if any, and not due to lens form or flexure when considering low-minus powered lenses. The clinician should reduce astigmatic power correction both to allow for minus tear lens effects in thicker meridians and to decrease variable visual results due to misrotation.

Contact Lenses↗
PubMed1989

Immunologic effects of extended-wear contact lenses.

All worn contact lenses are coated with materials from the tear film and the environment. Antigens are included in this complex and ever-present coating on the front and back surfaces of the worn contact lens. These deposited materials lead to insult of the conjunctival surface that influences mucus production and conjunctival-related comfort in the wearing of contact lenses.

Antigens↗
PubMed1985

Localized edema with soft toric contact lenses.

Soft toric contact lenses had provided a good correction for this patient for 3 1/2 years. An acute episode of slightly decreased vision and lens discomfort was accompanied by corneal irritation, edema, irregular distorted keratometric mires, and a change in refractive cylinder. It is of interest that the areas of most corneal disturbance were in continuous apposition to the areas of most deposits on the non-rotating toric contact lenses.

Adolescent↗
PubMed1997

Conjunctival impression cytology in patients wearing contact lenses.

PURPOSE: Evaluation of contact lens-induced cytologic changes on the conjunctival surface. METHODS: Fifty eyes of 25 patients wearing soft or rigid gas-permeable contact lenses, and 50 healthy eyes of 25 control subjects were examined with conjunctival impression cytology. Of the patients wearing contact lenses, 40% did not have any contact lens-related complaints, whereas 60% had some minor complaints related to contact lens intolerance. The material obtained by impression cytology was examined with regard to epithelial cell morphology, goblet cell density, and snake-like nuclear chromatin changes. RESULTS: When epithelial cell morphology was graded according to the system described by Nelson, specimens from the control group revealed 90% of the eyes to be grade 0 and 10% to be grade 1, whereas of the eyes wearing contact lenses, 8% were grade 0, 36% grade 1, 32% grade 2, and 24% grade 3. Thus statistically significant differences were observed between the control group and the contact lens group with regard to each grade (p < 0.05) as well as to the goblet cell densities (p < 0.05). Snake-like chromatin changes, on the other hand, were observed in 30 and 27% of the eyes wearing soft and rigid gas-permeable contact lenses, respectively, whereas these were not encountered in any eye in the control group. CONCLUSION: Epithelial changes were noted to be more frequent and more severe in symptomatic patients than in those without any complaints. No correlation was found between average duration of contact lens wear and the risk of contact lens intolerance or development of squamous metaplasia.

Biopsy↗
PubMed1987

The use of contact lenses by USAF aviators.

Contact lenses are an alternative method to spectacles for correcting refractive errors, but the U.S. Air Force prohibits the wearing of contact lenses by all aircrew members unless medically or optically indicated (AFR 167-3). USAFSAM has a clinical contact lens study consisting of 55 individuals wearing contact lenses for eye defects such as keratoconus, aphakia, anisometropia, and other special indications. Of these 55 individuals, 33 had medical conditions affecting their vision and were unconditionally grounded. Of these individuals, 31 (18 of 19 pilots, 8 of 9 navigators, 5 of 5 other categories) were visually rehabilitated and returned to full flight status by the use of contact lenses. Hard lenses were used in 70% of the cases and soft lenses in 30%. The large number of USAF aviators required to wear spectacles and new head-borne equipment has created compatibility problems with the standard USAF aviators' spectacle. For this spectacle compatibility problem, contact lenses appear as a viable alternative. However, for wide-spread use, concerns remain about the potential aviation hazards, such as +Gz effects, bubble formation, and corneal hypoxia.

Aerospace Medicine↗
PubMed1991

Disposable contact lenses.

Disposable soft contact lenses are an alternative to conventional extended-wear lenses and provide an acceptable margin of safety and convenience for the wearer. The lenses are worn for one to two weeks and then discarded. Buildup of tear film deposits is minimized, and the need for cleaning and disinfecting solutions is eliminated. The long-term safety of disposable contact lenses is unknown.

Conjunctivitis↗
PubMed1985

Pneumatonometry through bandage contact lenses.

Bandage soft contact lenses are an effective therapy for patients with a variety of corneal diseases. These patients often require accurate measurement of the intraocular pressure, necessitating movement or removal of the contact lens for slit-lamp Goldmann applanation tonometry. Intraocular pressure was measured in 21 normal, healthy volunteers, using a pneumatonometer (Alcon). A therapeutic soft contact lens (Plano T) was then placed on the eye and the pneumatonometer was used to remeasure the intraocular pressure through the contact lens. The average intraocular pressure without the contact lens was not statistically different from the intraocular pressure with the contact lens. These data suggest that pneumatonometry is an effective way to assess the intraocular pressure in patients wearing bandage contact lenses, thus eliminating the need to manipulate the lens solely for the purpose of intraocular pressure determination.

Adolescent↗
PubMed1993

The role of pili in the attachment of Pseudomonas aeruginosa to unworn hydrogel contact lenses.

Contamination of contact lenses is thought to increase the risk of infectious keratitis, yet factors promoting attachment of bacteria to contact lenses are not fully understood. It has been suggested that strains of Pseudomonas aeruginosa attach to mucosal surfaces via pili which are appendages found on some strains. This study investigated the role of pili and the effect of incubation time on the attachment of P. aeruginosa to 20 unworn hydrogel lenses representative of each of the four FDA categories. Ten lenses were incubated for 15 minutes and another ten for 180 minutes. Lenses were incubated with either PAK + P. aeruginosa which possessed pili or its isogenic mutant pair, PAK-, which was genetically similar except for the absence of pili. Bacteria were quantified, following homogenization of the contact lens, by viable counts. Non-piliated bacteria were significantly more likely to adhere to the lenses (p < 0.001). A significant interaction between lens type and incubation time was observed (p < 0.05); thus it is difficult to generalize about either of these effects in isolation. These results show that surface characteristics may confer an attachment advantage to bacteria.

Bacterial Adhesion↗
PubMed1975

Bifocal contact lenses today.

Bifocal contact lenses produced today are far from perfection; however, there are several different types produced, one of which should work out for most presbyopic patients who can be successfully fit with single vision contact lenses. This paper looks at the products we have available now. It is not designed to be a cookbook that the optometric practitioner can follow from A to Z and come up with the ideal contact lens bifocal fit. It is pointed at making the optometrist aware of the growing population of contact lens wearers that the health professions are now creating, and a resume of the products and fitting techniques now available to the eye care field.

Contact Lenses↗
PubMed1998

Pediatric contact lenses: case reports.

BACKGROUND: Contact lenses may be a useful, even essential, treatment modality for children with a variety of optometric needs. Many clinicians who are experienced and capable contact lens practitioners but do not specialize in the care of children may refrain from considering contact lenses as a treatment option because of a host of perceived problems. Most of these concerns can be readily overcome with patience, planning, and education. CASE REPORTS: Five cases are presented to illustrate specific clinical problems and the clinical application of contact lenses in the pediatric population. CONCLUSION: The case reports illustrate the clinical application of contact lens fitting in children with a variety of clinical needs. The use of contact lenses in children is an ongoing process, requiring great flexibility and creativity on the part of the optometrist. Educating the child and the family is an integral part of the treatment. The use of contact lenses in children is both an opportunity and a challenge that may result in great satisfaction for the child, the family, and the optometrist.

Accommodation, Ocular↗
PubMed1998

Applications of Raman spectroscopy to ophthalmology: spectroscopic characterization of disposable soft contact lenses.

Disposable soft contact lenses based on HEMA-MAA hydrogels are examined using Raman and ATR/FTIR vibrational spectroscopies and thermal analysis. The main factors dealing with physical, chemical, and biological biocompatibility are evaluated in relation to those of long-wear soft contact lenses with the aim of individuating the most biocompatible lens. The Raman spectra of HEMA-MAA lenses show that some biocompatibility factors are affected by environmental conditions and, in particular, by changes in pH and ionic strength values.

Biocompatible Materials↗
PubMed1998

An alternative approach to bandage contact lenses.

PURPOSE: Therapeutic bandage contact lenses have been used in the management of a variety of corneal and anterior segment disorders. However, clinical experience with the therapeutic use of disposable contact lenses is limited. The present study was designed to evaluate the efficacy of disposable contact lenses as bandage lenses in anterior segment disorders. METHODS: We fit 45 patients who had various corneal and anterior segment disorders with disposable contact lenses (42% etafilcon A and 58% water content). We used this lens as a healing and surgical adjunct and for structural support and symptomatic relief. Patients were followed for a minimum period of 3 months. Therapeutic efficacy and complications were evaluated. RESULTS: Eighty-two percent of patients were fit successfully. Ninety-one percent of the successfully fit patients were therapeutic successes. Disposable lenses were found to be very useful in the management of epithelial abnormalities and as surgical adjuncts. Dry eye was the most frequent cause of contact lens associated therapeutic failure. Complications included contact lens deposits, lens loss, and corneal neovascularization. CONCLUSIONS: The use of disposable lenses was most effective in conditions requiring short-term lens use where one to two lens applications were sufficient to allow healing, making disposable lenses a very convenient and cost-effective alternative to conventional therapeutic bandage contact lenses. For reasons of cost, disposable lenses were not a viable alternative in conditions requiring therapeutic lens use for long periods of time.

Adult↗
PubMed1996

The clinical use of contact lenses and collagen shields.

Contact lens wear before and after photorefractive or phototherapeutic keratectomy with excimer lasers has become an increasingly interesting subject. No negative side effects of contact lens wear prior to photorefractive keratectomy have yet been shown and refractive errors postoperatively do not seem to constitute a major practical problem. Normal side effects include the risk of bacterial infection and keratitis. The major pathogen in this context is still Pseudomonas aeruginosa, although increased insight into the mechanisms of bacterial adhesion and improvements in cleaning procedures now allow more effective preventive care of contact lenses themselves and of contact lens cases. Tear fluid research using leucotriene C4 as a possible indicator for subclinical inflammation has led to interesting results, and the importance of the arachidonic pathway and its metabolites has become more evident. These advances contribute considerably to the safe use of contact lenses in clinical ophthalmology, although major innovations such as the multifocal contact lenses have not reached the stage of perfection.

Animals↗
PubMed1993

CCLRU standards for success of daily and extended wear contact lenses.

Success in contact lens wear is often judged on the basis of patient "survival" rather than the achievement of satisfactory performance based on specific criteria. In 1971, Sarver and Harris defined a series of standards for successful polymethyl methacrylate (PMMA) lens wear which incorporated criteria for wearing time, comfort, vision, ocular tissue changes, and patient appearance. In this paper we propose a revision of these criteria based on current understanding of the ocular response to contact lens wear. These revised CCLRU (Cornea and Contact Lens Research Unit) standards for success are intended as realistic performance objectives, and can be applied in clinical trials to evaluate and compare the clinical performance of present and future rigid and soft contact lenses, worn for daily and extended wear.

Contact Lenses↗