The CLAO journal : official publication of the Contact Lens Association of Ophthalmologists, Inc最新文献

Purpose: To review the diagnosis, microbial and pathological features, pathogenesis, and treatment of infectious crystalline keratopathy (ICK).

Methods: We reviewed the literature on infectious crystalline keratopathy.

Results and conclusions: ICK is an indolent corneal infection in which needle-like, branching crystalline opacities are seen within the corneal stroma, in the absence of appreciable corneal or anterior segment inflammation. In most cases it occurs as a complication of corneal surgery and keratitis, with an alpha-hemolytic Streptococcus being the cause of infection. Discontinuation of topical steroids with aggressive antibiotic therapy may suffice, but continued infection, vascularization, or scar formation may affect visual acuity and require penetrating keratoplasty.

Purpose: The purpose of this study was to evaluate the immunology, pathogenesis and therapy of Acanthamoeba keratitis.

Methods: The recent development of an animal model of Acanthamoeba keratitis and its impact on the medical treatment and immunology of Acanthamoeba keratitis was reviewed.

Results: After initial reports, Acanthamoeba infection of the cornea remained a rare disease until an association with contact lens wear was first recognized. Although the disease is closely associated with contact lens wear, it appeared that the contaminated solutions that were coming into contact with the lenses caused the disease. All types of contact lenses can be associated with development of Acanthamoeba keratitis. Therefore, the contact lens serves as a carrier of Acanthamoeba to the surface of the eye. The typical patient with Acanthamoeba keratitis is a young healthy individual who is either a contact lens wearer or has had significant exposure to water contaminated with Acanthamoeba. There are several risk factors such as corneal trauma, contaminated solution and contact lenses that have been reported to be associated with Acanthamoeba keratitis. In spite of significant improvement in the diagnosis of Acanthamoeba keratitis, progress in developing and utilizing effective antimicrobial agents for treating this disease have been disappointing. A growing body of evidence suggests that the mammalian immune system, if properly activated, is capable of preventing and controlling ocular infections.

Conclusions: In order to develop effective immunotherapeutic modalities, and to better understand the immune effector mechanisms that protect the cornea against Acanthamoeba infection, it is necessary to fully characterize and evaluate the immunobiology of Acanthamoeba keratitis.

Purpose: The purpose of this study was to measure improvement in best corrected visual acuity with rigid gas permeable (RGP) contact lenses compared to best corrected spectacle visual acuity for patients with irregular astigmatism.

Methods: We compared best corrected visual acuity obtained with spectacle correction to best corrected visual acuity obtained with rigid gas permeable contact lenses for forty-eight eyes of 29 patients with irregular astigmatism.

Results: Patients with 20/20 spectacle visual acuity achieved, on average, no improvement in visual acuity with RGP contact lenses. Patients with 20/25-20/30 spectacle visual acuity achieved a one line average improvement. Patients with 20/40 spectacle visual acuity achieved a two line average improvement. Patients with 20/50-20/200 spectacle visual acuity achieved a four line average improvement and patients with spectacle visual acuity of 20/400, a six line average improvement.

Conclusions: RGP contact lenses can provide a significant improvement in visual acuity compared to spectacle correction for patients with irregular astigmatism.

Purpose: To evaluate the bacterial contamination of bandage disposable soft contact lenses used in patients following photorefractive keratectomy (PRK) and to correlate our findings with clinical data.

Methods: Forty-six patients (81 eyes) underwent PRK. Immediately after each procedure, disposable soft contact lenses were positioned with sterile forceps. After 3 days, the lenses were removed in a sterile manner, placed in sterile Eppendorf pipettes containing 8 mL of enriched brain heart infusion broth, and analyzed for microbial contamination.

Results: Seven positive cultures were found: six gram positive cocci (7.4%) and one gram negative bacillus (1.2%). There was no clinical correlation with these findings.

Conclusion: Isolated microorganisms were similar to those described in the literature as agents of bacterial keratitis and are components of the normal ocular flora. Klebsiela pneumoniae--considered an occasional or transient flora--was the exception. All isolated microorganisms but K. pneumoniae were sensitive to most of the antibiotics tested. Our findings suggest that the risk of infectious keratitis after PRK related to soft contact lens wear for 3 days seems to be low, which may be because lenses were not manipulated by the patient during the wearing period, and the postoperative antibiotic regimen was strictly followed by patients. However, care should be taken to instruct patients in proper lens care practices to reduce the risk of bacterial keratitis in contact lens wear following PRK.

Purpose: Keratoconus is a diseasethat has been recognized clinically for many years. However, it is only more recently that a better understanding has been achieved in the area of keratoconus pathogenesis. The purpose of this paper is to summarize the completed research, review ongoing studies, and present a hypothesis for keratoconus pathology.

Methods: We used immunochemistry and molecular techniques to characterize keratoconus corneas.

Results and conclusions: Our hypothesis attempts to incorporate many of the recognized biochemical and molecular abnormalities found in the keratoconus corneas. Our hypothesis states: 1) there is abnormal processing of the free radicals and superoxides within the keratoconus corneas; 2) there is a build-up of destructive aldehydes or peroxynitrites within the corneas; 3) the cells that are damaged irreversibly undergo the process of apoptosis; and 4) the cells that are damaged reversibly undergo wound healing or repair. As part of the wound healing process, various degradative enzymes and wound healing factors are upregulated, which leads to focal areas of corneal thinning and fibrosis. Future studies will be directed to testthis working hypothesis and determine if these theories are valid.

Purpose: We describe a practical method to qualitatively identify polymethylmethacrylate (PMMA) and rigid gas permeable (RGP) contact lens materials.

Methods: By progressive dilution of a saturated saline solution made with distilled or tap water and sodium chloride, we recorded comparative densitometry of rigid contact lens materials using a small hydrometer or by liquid displacement.

Results: The method was sensitive enough to separate the polymethylmethacrylate, all silicon-methacrylates, and all but two fluorine-containing silicon-methacrylates. The hydrometer had a precision of three decimals rounded to the nearest 0.005. There was only one RGP product that could have been confused with the PMMA material. Most silicon-methacrylates had lower densities than fluorine containing silicon-methacrylates. Only four of 25 products under 1.117 gm/cm3 contained fluorine.

Conclusions: Densitometry with a hydrometer is an effective non-destructive method to identify RGP materials and to verify their quality. The method is easier when lens blanks are tested, but in spite of differences in shape, size, and weight, densitometry may also be used with new or used contact lenses. Its simplicity and low cost makes densitometry feasible for any contact lens laboratory or clinic to use on a routine basis. Only silicon-methacrylates had an inverse relationship between density and oxygen permeability. As the silicon content of the contact lens increases, the Dk increases and the density decreases.

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.

Purpose: We conducted a 15-month prospective clinical studyto evaluate the performance of the Acuvue Bifocal contact lens and to determine the objective and subjective factors that influence patient success rates in a general presbyopic population presenting to a contact lens specialist's office.

Methods: The first 100 patients who were initially fit and dispensed the Acuvue Bifocal contact lens are included in this study data. At each follow-up visit, visual acuity, slit lamp evaluation of lens/cornea relationship, and any change in ocular surface characteristics were noted. The study population was a general population with an interest in wearing disposable multifocal contact lenses. Success was defined as the patient actually purchasing the lens for continual wear.

Results: The overall success rate with the lens in this diverse study group was 53%. The majority of the successful patients achieved 20/25 or better distance and near acuity with the Acuvue Bifocal. None of the study participants had any adverse effect of lens wear or changes in keratometry or ocular surface characteristics. Of the successful patients, 57% wore the lens in a binocular fashion, while the remainder used some form of monovision. Virtually all patients rated lens comfort as excellent or very good, with the major factor in success or failure being visual performance.

Conclusions: This prospective study in an average group of presbyopic contact lens or spectacle wearers yielded valuable insights into the performance of a disposable multifocal contact lens in a general contact lens practice. The Acuvue Bifocal should prove to be a valuable addition to the contact lens fitter's practice.

Purpose: We compared the antimicrobial activity of a new multi-purpose disinfection solution (OPTI-FREE EXPRESS with ALDOX) to a 3% hydrogen peroxide disinfecting system. The antimicrobial ingredients in the new solution are polyquaternium-1 and myristamidopropyl dimethylamine.

Methods: The solutions were tested for antimicrobial activity against Staphylococcus sp.., Pseudomonas aeruginosa, Serratia marcescens, Candida albicans, Fusarium solani, and two Acanthamoeba species and were evaluated according to the primary criteria of the FDA and ISO contact lens disinfection procedures.

Results and conclusions: OPTI-FREE EXPRESS with ALDOX (EXPRESS MPDS) Multi-Purpose Disinfecting Solution provided a multiple spectrum of antimicrobial activity and met the FDA and ISO primary Stand Alone Test criteria for disinfection of contact lenses. EXPRESS MPDS showed disinfection activity in the range of a 3% hydrogen peroxide system. Unlike the 3% hydrogen peroxide system, it retarded contamination during storage.