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Results for “CONTACT LENSES”

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At least 19 recordsLinked to original sources
PubMed2003

Kersley lecture: eye believe in contact lenses: contact lenses and/or refractive surgery.

PURPOSE: Media publicity has made patients increasingly aware that surgical vision correction is available. This article gives an overview on refractive surgery and contact lenses. METHODS: Contact lens and refractive surgery possibilities are highlighted for patients with myopia, hyperopia, astigmatism, presbyopia, aphakia, and keratoconus. Therapeutic, pediatric, and cosmetic indications are discussed. RESULTS: Refractive surgery is beneficial for low refractive errors. The use of contact lenses is mandatory in cases of monovision and strabismus before refractive surgery and beneficial for therapeutic use postoperatively. CONCLUSION: Although many patients are always best corrected with contact lenses, only the right synergism of contact lenses and refractive surgery will benefit patients.

Contact Lenses↗
PubMed1990

Ultraviolet-absorbing spectacle lenses, contact lenses, and intraocular lenses.

Optical materials that are available to the practitioner for protection of the eye against hazardous exposure to ultraviolet radiation (UVR) are discussed. Principles of protection, procedures for calculating safe ocular exposure duration, and transmittance curves of commonly prescribed spectacle lenses, contact lenses, and intraocular lenses are discussed. Suggestions are made to assist the practitioner in providing adequate protection for the patient.

Animals↗
PubMedDate not supplied

[The prescription of soft contact lenses].

Contact lenses represent a modern way to correct the refraction errors, the main beneficiaries being the myopes, the anisometropes, the mono- or bilateral aphakias when there was not performed an intraocular lens implantation, the astigmates and the hyperopes; with the natural tint contact lenses the interest will extend over the emmetropic patients. The ophthalmologist has the capacity to settle the indications and contraindications (general and ocular diseases, hygiene deficiencies etc) of wearing contact lenses, as if to prescribe the contact lenses and to teach the patient how to handle and how to take care of his contact lenses. Having the idea to broke a certain restraint which is shown by many ophthalmologists concerning contact lenses, we have stated some practical considerations regarding the method to prescribe contact lenses.

Contact Lenses, Hydrophilic↗
PubMed1995

Adherence of cysts and trophozoites of Acanthamoeba to unworn rigid gas permeable and soft contact lenses.

Contact lens related Acanthamoeba keratitis has been more often associated with the use of soft contact lenses than with the use of rigid gas permeable (RGP) contact lenses. We studied the adherence of Acanthamoeba cysts and trophozoites to unworn RGP (silicone acrylate and fluoropolymer) and low and high water content soft contact lenses marketed in India. A human corneal isolate of Acanthamoeba polyphaga suspended in saline (1 x 10(5) amoebae/mL) was used. Lens segments were exposed to A. polyphaga cysts or trophozoites with or without shaking. After exposure for zero to 7 hours, lenses were either washed or not washed and the adherence was determined using light microscopy and a hemocytometer (per square millimeter of the lens). Both cysts and trophozoites immediately adhered to all four types of lenses. Adhesion increased with an increase in exposure time. The number of adherent cysts and trophozoites was higher (P = 0.043-0.0003) in the unwashed group of lenses at all exposure times for all lenses. Among washed groups, adherence was greatest with RGP silicone acrylate and high water content soft lenses. Trophozoites of Acanthamoeba showed greater adherence to RGP lenses, whereas cysts showed greater adherence to high water content soft lenses. Shaking did not have a significant effect on adherence. Adhesion of Acanthamoeba to contact lenses may play an important role in the pathogenesis of Acanthamoeba keratitis.

Acanthamoeba↗
PubMed1989

Adherence of Acanthamoeba castellanii cysts and trophozoites to unworn soft contact lenses.

Contact lens-related Acanthamoeba keratitis has been associated with the use of soft contact lenses and homemade saline solutions. We studied the adherence of Acanthamoeba to unworn extended-wear soft contact lenses on a human corneal isolate of Acanthamoeba castellanii suspended in normal saline (cysts, 6.3 x 10(5)/ml; trophozoites, 3.6 x 10(5)/ml). Unworn hydrogel contact lenses (polymacon, water content 38.6%; 50 lenses, 400 lens segments) were exposed to A. castellanii cysts or trophozoites with or without stirring. After exposure for zero to seven hours, soft contact lenses were or were not washed, and the A. castellanii adherence was determined with a standardized light-microscopy technique (40 fields, ten lens segments for each count) and with scanning electron microscopy. Both cysts and trophozoites adhered to the unworn soft contact lenses. Trophozoites showed acanthopodia, lobopodia, and filopodia. This study indicates that both A. castellanii cysts and trophozoites can firmly adhere to unworn soft contact lens. Such adherence may play a role in the pathogenesis of soft contact lens-related Acanthamoeba keratitis.

Acanthamoeba↗
PubMed1993

Optical performance of decentered bifocal contact lenses.

Contact lenses frequently do not center over the pupil. The potential changes in optical performance introduced by poor centration of bifocal contact lenses have only been described previously from theoretical considerations. The present study measured the modulation transfer function (MTF) of rigid concentric-design refractive and rigid diffractive bifocal contact lenses with varying apertures and amounts of decentration. Decentration was shown to have a greater effect on the MTF of the refractive than on the MTF of the diffractive bifocals. The MTF of the refractive bifocals was related to the proportion of the aperture covered by the central optic zone (COZ). Unexpectedly, the MTF of the distance focus of the diffractive bifocal contact lenses was reduced at moderately high spatial frequencies. The practitioner should be aware of the effects of decentration of bifocal contact lenses.

Contact Lenses↗
PubMed1999

Microbiological evaluation of contact lenses and contact lens disinfection solutions in an asymptomatic population and in medical personnel.

PURPOSE: To compare the contamination of contact lenses and contact lens disinfection solutions in a population of contact lenses wearers comprised of medical personnel and non-medical subjects. METHODS: Forty-six medical personnel working in an infectious environment and 35 non-medical subjects were enrolled in the study. Contact lenses and contact lens disinfecting solutions were cultured and potential pathogens were isolated. RESULTS: The frequency of isolation of pathogens from the contact lenses of medical personnel was significantly higher than from non-medical subjects. There was no growth in both the contact lens and the disinfecting solution cultures in 56.5% of the subjects in the medical personnel group, and in 57.1% of non-medical group of subjects. Both the contact lens and disinfecting solution cultures were positive in 21.7% of the medical personnel group, while in the non-medical group, only 2.9% of subjects had positive cultures. CONCLUSIONS: Microbacterial contamination of contact lenses and disinfection solution was more frequent in the medical personnel group compared with non-medical subjects. In the medical personnel group, the most frequently isolated microorganism was Staphylococcus albus (19.8%), which is seen in hospital infections. Because soft and rigid gas permeable contact lens usage was approximately equal, we conclude that medical personnel are more prone to contamination.

Adolescent↗
PubMedDate not supplied

[Method of computing the geometrical parameters of contact lenses].

Contact lenses of home-made production are classified, and the methodology of computing their structural elements for several types of lenses is presented. Some design features of the parameters are considered with regard to the properties of the water-receptive material used for soft lenses.

Contact Lenses↗
PubMed2003

Corneal hypoxia secondary to contact lenses: the effect of high-Dk lenses.

Contact lenses made from materials of low-oxygen permeability (Dk) do not meet the oxygen requirements of the cornea for overnight wear. Long-term extended wear of these lenses results in chronic changes to all layers of the cornea, many of which are associated with hypoxia. High-Dk silicone hydrogel and gas permeable lenses are now available for 30-night continuous wear. The high-oxygen transmissibilities of these lenses have enabled the development of a successful continuous wear modality by eliminating the hypoxic effects of long-term wear. Presently, the focus is on improving lens performance by developing lenses that are more biocompatible, provide greater comfort, and maintain a stable tear film without inflammatory or mechanically induced adverse events.

Contact Lenses↗
PubMed1997

[Contact lenses. 2: Contact lens associated infections].

Contact lens wearers, especially those who wear soft or extended wear contact lenses, are at increased risk of suffering from keratitis. Among the causes of corneal infections, an inadequate hygiene or overextended wear play an important role. An insufficient cleaning and disinfection leads to contamination with pathological germs. Sites of entry for these germs are corneal microlesions, caused by the setting and removal of contact lenses, and epithelial defects, as a result of the wearing of old or defective contact lenses. Primary eye diseases of patients who wear contact lenses can be altered by their wearing, and vice-versa. Even more, miscellaneous infections may lead to infectious corneal ulcerations. Having an adequate hygiene, a proper patient orientation during the medical visit, and a regular control are therefore of great importance for the reduction in the frequency of such infections by patients who wear contact lenses.

Contact Lenses↗
PubMed1995

The effect of Acanthamoeba concentration on adherence to four types of unworn soft contact lenses.

Contact lens wear is a predominant risk factor for Acanthamoeba keratitis. The exact nature of the relationship between organism concentration and contact lens adherence is poorly understood. We investigated the effect of Acanthamoeba inoculation concentration on adherence to four categories of contact lenses of varying polymers and water content. Acanthamoeba polyphaga was harvested in log growth phase at 5 days subculture and suspended in PBS at concentrations of 1 x 10(2), 10(3), 10(4), 10(5), and 10(6) organisms/mL (trophozoite:cyst ratio 90:10 +/- 2). Sterile unworn polymacon, etafilcon, lidofilcon, and bufilcon contact lens segments were exposed to Acanthamoeba for 2 hours. Acanthamoeba adherence was quantified using phase contrast microscopy. For all lens types, trophozoite adherence increased as the concentration of inoculum increased, but the relationship was not directly proportional. In all cases the minimal adherence was observed at 10(2). Trophozoite adherence increased disproportionate to cysts for all contact lens types. The greatest adherence was to lidofilcon lenses. At all concentrations adherence was greater to lidofilcon than etafilcon or polymacon, and greater to bufilcon than etafilcon or polymacon at the P < 0.01 level. Adherence was significantly greater to lidofilcon than bufilcon only at 1 x 10(5) and 10(6); P < 0.05 (ANOVA). This study suggests that adherence of A. polyphaga to contact lenses increases with the number of organisms in the inoculum, but the relationship is not directly proportional. The number of adherent organisms varies by contact lens type, with the greatest adherence to lidofilcon and the least to etafilcon lenses.

Acanthamoeba↗
PubMed1997

[Contact lenses. 1: Contact lens associated complications].

The contactology as frontier between ophthalmology and eye optics requires special attention by part of ophthalmologists. Contact lenses influence the anatomy, the physiology and the immunological responses of the external eye. The corneal metabolic disorders of contact lens wearers are among others, the result of a diminished oxygen supply to the cornea. These disorders are influenced by contact lens deposits, tear film dysfunction and intrinsical characteristics of contact lenses. Sensibilisation and allergic reactions are result of the wearing of contact lenses. Even toxic reactions, as a result of the disinfection systems used, may be observed Ophthalmologists must be able to recognize the contact lens induced diseases and to advice their patients properly. Therefore, regular ophthalmological control examinations are indispensable.

Conjunctival Diseases↗