PubMed · 7239815
The source did not provide an abstract. Follow the original record for more information.
Explore connections, maps & timelines
R M Hill. 1981. Laboratory studies.. https://pubmed.ncbi.nlm.nih.gov/7239815/
Cite the original work for its findings. Save a collection to share your selection of sources.
KEEP EXPLORING
BACKGROUND: The conventional vertometer (lensometer) is difficult to use for accurate measurement of contact lenses whose back vertex power (BVP) varies across the optic zone. BVPs of multifocal rigid and soft contact lenses have previously been measured using a conventional vertometer incorporating the Scheiner principle, which makes use of two light paths equidistant from the center of the lens. METHODS: We have developed a computer-based vertometer system based on the Scheiner principle which can be used to produce a profile of BVPs across rigid and soft contact lenses. A computer interface to the vertometer allows rapid acquisition of readings and software-based ray tracing derives in-air dioptric power readings across the optic zone at specific ray heights. RESULTS: Results are presented for soft and rigid, and spherical and aspheric surface contact lenses. CONCLUSIONS: The system improves the measurement resolution of a standard vertometer and shows an acceptable level of precision and accuracy for most applications.
Keratitis due to Nocardia farcinica occurred in a 49-year-old female after inappropriate cleaning of her semipermeable rigid contact lenses with basin-stored water during a holiday in France. N. farcinica was differentiated from Nocardia asteroides by its growth at 45 degrees C, acid production from rhamnose, its opacification of Middlebrook 7H10 agar, and its marked degree of resistance to all cephalosporins, aminoglycosides, tetracyclins, macrolides, and trimethoprim-sulfamethoxazole. To the best of our knowledge, this is the first reported case of human N. farcinica keratitis, confirming that this microorganism can be responsible for serious human disease.
PURPOSE: To put into perspective the individual risk and the societal burden of contact lens microbial keratitis. METHODS: I reviewed the available epidemiologic data on contact lens microbial keratitis with emphasis on distinguishing microbial from nonmicrobial keratitis, determining the incidence of the disease, the relative risk with different styles of contact lenses, and the risk factors. RESULTS: Contact lens wear can be classified in multiple different ways (indications for wear, contact lens material, wearing schedule, and replacement schedule). Adverse effects of contact lens wear on the cornea have been documented by several studies. Distinction between aseptic and septic focal infiltrates is discussed. The incidence rates for bacterial microbial keratitis range from approximately two/10,000 per year for rigid contact lens, 2.2-4.1/10,000 per year for daily-wear soft contact lens, to 13.3-20.9/10,000 per year for extended-wear soft contact lenses. The risk with therapeutic contact lenses is much higher: approximately 52/10,000 per year. Comparative studies suggest that the relative risk of microbial keratitis is approximately 1 for rigid gas-permeable lenses (RGPs; the referent), 0.5-2.74 for polymethylmethacrylate (PMMA), 1.0-4.2 for daily-wear soft contact lenses, 2.7-36.8 for extended-wear soft contact lenses, and 13.0-13.3 for disposable soft contact lens wear. The most significant risk factors include overnight wear, smoking, male sex, and socioeconomic status. CONCLUSIONS: There is a significant health concern for the 26 million wearers of contact lenses with some potentially modifiable risk factors. Identification of the risk factors and further studies of the pathogenesis allow contact lens manufacturers to direct research efforts and practitioners to provide better information and informed consent to patients.