Malvina B. Eydelman

Standardized analyses of correction of astigmatism by laser systems that reshape the cornea.

PURPOSEnTo develop a minimum set of analyses and a format for presentation of outcomes of astigmatism correction by laser systems that reshape the cornea.nnnMETHODSnAn Astigmatism Project group was created under the auspices of the American National Standards Institute (ANSI) Z80.11 Working Group on Laser Systems for Corneal Reshaping. The Astigmatism Project Group was made up of experts in astigmatism analyses from academia, government, and industry. An extensive literature review was conducted to identify all currently available methodologies for the evaluation of astigmatic outcomes. Project Group members discussed the utility of each method and its specific parameters for evaluating the effectiveness of astigmatism-correcting devices. They gave consideration to unique terminology and analyses required for evaluation of correction of astigmatism by laser systems that reshape the comea.nnnRESULTSnThe Project Group defined a comprehensive list of analysis variables needed for the evaluation of astigmatism-correcting devices and generated a mathematical definition for each term. They developed a minimum set of analyses needed for evaluation of astigmatism treatments by laser systems that reshape the cornea. They established methods for calculating the refractive error analysis variables and constructed recommended table and graph formats for data presentation.nnnCONCLUSIONSnThis article contains the recommendations of the Astigmatism Project Group of the American National Standards Institute. We propose it as a standard reference for astigmatic refractive error analyses for the evaluation of safety and effectiveness of laser systems that reshape the cornea.

Strategies to optimize conditions for testing multipurpose contact lens solution efficacy against Acanthamoeba.

Objectives: To optimize the growth, culture, and life cycle conditions for testing multipurpose solutions (MPS) against Acanthamoebatrophozoites and cysts to better inform the development of an appropriate test protocol. Methods: Two strains of Acanthamoeba castellanii were grown using 2 different methods, bacterized and axenic. Amoebae grown from both methods and from both strains were treated with 4 different MPS as trophozoites and cysts, which were generated using 4 encystment methods. Experiments were run in triplicate with controls. A 5-tube most probable number method was used to enumerate the survivors and to determine the log kills. Statistical analysis was performed using effect screening. Results: There was a marked difference in effectiveness among solutions, which varied with growth conditions (P<0.0001) and encystment method. Growth medium affected survival. In addition, there was a significant difference in cyst survival, which was dependent on encystment method (P=0.0013). The strain used was less of a factor in trophozoite resistance to MPS. Cyst resistance to MPS varied depending on which strain was used, but it was not a significant factor. Conclusions: When designing a contact lens solution efficacy testing protocol for Acanthamoeba, care should be taken to control for variables that may distort results. An appropriate protocol should include growing Acanthamoeba bacterized and allowing them to encyst naturally. By choosing optimized testing conditions, a more realistic efficacy of contact lens solutions can be determined which will result in better and safer products on the market.

The effects of contact lens materials on a multipurpose contact lens solution disinfection activity against Staphylococcus aureus.

Objectives: To determine the effect of 8 different lens materials on polyhexamethylene biguanide (PHMB) concentration in multipurpose solution (MPS) levels over time and to determine the effect of lenses on lens solution microbial efficacy over time. Methods: Silicone hydrogel lenses and conventional hydrogel lenses were soaked in polypropylene lens cases filled with contact lens MPS containing 1 ppm PHMB for 6, 12, 24, 72, and 168 hours. Cases filled with the same solution without lenses were controls. After each time period, solutions from cases with the 8 types of lenses and controls were assayed for activity against Staphylococcus aureus according to International Organization for Standardization-14729 with modifications. Solutions were analyzed for PHMB concentration at each time point. Results: Some of the different lens materials significantly affected the PHMB concentration (P<0.0001) and the biocidal efficacy. Etafilcon A lenses significantly decreased PHMB levels after only 6 hours of lens soak time. The product lot of MPS used was also significant (P<0.0001). Enfilcon A, senofilcon A, and lotrafilcon B lenses did not significantly decrease PHMB levels. Conclusions: The efficacy of MPS was affected by some lens materials and PHMB concentration. Lens materials differ in their effect on PHMB concentration and the subsequent efficacy of the MPS. Over time, some lens materials can significantly reduce the PHMB concentration and the MPSs microbial activity against S. aureus.

Food and Drug Administration Efforts to Mitigate Contact Lens Discomfort

The premarket review of contact lenses and accessories by the FDA involves the assessment of nonclinical and clinical information in support of clearance or approval of marketing applications. The review process for these medical devices, including attributes, which may contribute to comfort for lens wearers, is summarized, as are mechanisms by which FDA continues to assess and improve recommendations through the review process and through collaboration with external entities.