Skin adhesives and skin adhesion. 1. Transdermal drug delivery systems.

The use of pressure-sensitive adhesives (PSAs) for skin-contact applications is discussed. The requirements of such adhesives in various applications are examined in detail. Commercially available classes of PSAs used for skin-contact applications are the acrylics, the polyisobutylenes, and the silicones. The main application examined in this review is transdermal drug delivery. The roles played by the PSA in two types of transdermal designs are described. Correlations between in vivo and ex vivo measurements of adhesion are discussed. Also, the reported human studies of various commercially available transdermals are examined critically, with a view to assessing the relative performance capabilities of each type of transdermal design. Finally, a comprehensive listing of currently commercialized transdermals is given.

Intraocular lens materials and styles: a review.

Biomaterial science has lead to the development of a variety of foldable intraocular lens (IOL) biomaterials. This literature review examines these lenses from both a basic science and a clinical perspective. By most parameters, hydrogel, soft acrylic and silicone IOL are better than polymethylmethacrylate (PMMA) lenses. Plate haptic silicone IOL have the lowest incidence of cystoid macula oedema and posterior capsule opacification, but these lenses require an intact anterior capsularhexis and posterior capsule. Yttrium aluminium garnet (YAG) laser capsulotomy must be delayed at least 3 months to avoid posterior lens dislocation. Silicone has the lowest threshold for YAG laser damage of all IOL materials and also adheres irreversibly to silicone oil with subsequent optical impairment. Three piece silicone IOL with polypropylene haptics have a higher incidence of decentration, pigment adherence and capsule opacification compared with PMMA haptics. Hydrogel lenses are very biocompatible and resistant to YAG laser damage, but pigment adheres to the surface more readily than PMMA. Soft acrylic IOL unfold slowly, resulting in controlled insertion, but it is possible to crack the lens and some lenses develop glistenings due to water accumulation. There are significant socioeconomic implications to the large differences in posterior capsule opacification rates between the various biomaterials and the lens styles.

Gas chromatographic and mass spectrometric purity analysis of acrylates and methacrylates used as patch test substances.

BACKGROUND: To make a correct diagnosis of allergic contact dermatitis, patch testing needs to be performed, and the patch test substances need to be pure. OBJECTIVE: We wanted to study how pure commercial (meth)acrylic patch test substances are. METHODS: The purity of (meth)acrylic patch test substances (diacrylates, dimethacrylates, and triacrylates) dissolved in acetone was determined by gas chromatography. The impurities were identified by mass spectrometry in both electron impact and chemical ionization mode. RESULTS: The analyzed dimethacrylates were very pure (97% to 99%). The purity of the three studied diacrylates were 81% to 91%, but tripropyleneglycol diacrylate (81% pure) contained as much as 13% of tripropyleneglycol monoacrylate. The purities of the triacrylates were 82% to 86%. All diacrylates and triacrylates contained 1% to 13% of the corresponding hydroxyacrylates. CONCLUSION: The impurities may result in false interpretation of the patch test results, and accordingly in wrong diagnosis. If the patch test substance is impure, at least, the chemical impurities that can be detected by gas chromatography should be measured and reported in a certificate of analysis, preferably from each batch.

Alterations to the AcrySof intraocular lens during folding.

PURPOSE: To determine the frequency and cause of scratches or marks on the AcrySof intraocular lens (IOL). SETTING: Centre SaintVictor, Amiens Cédex, France. METHODS: In a clinical study, an AcrySof IOL was implanted in four eyes using a McDonald-Livernois forceps. In an experimental study, 50 sterile AcrySof IOLs were folded under a surgical microscope by one person; 40 were folded with a modified Steinert forceps and 10, with a modified Buratto forceps. RESULTS: Three IOLs implanted in the clinical study had scratches, marks, or both. These were noted during surgery but were not significant enough to justify explantation. They had no effect on recovery of vision. Of the 50 IOLs studied microscopically, 18 showed no defects; 32 had some alterations that were difficult to assess because they were minimal or because more than one alteration appeared on the same lens. CONCLUSION: AcrySof IOLs are more fragile than silicone IOLs, although the alterations caused by folding did not affect visual acuity in this study. To avoid complications, the lens must be folded on the 6 to 12 o'clock axis and the haptics inserted one right after the other.

Effect of folding on the optical quality of soft acrylic intraocular lenses.

PURPOSE: To assess the effect of folding procedures on modulation transfer function (MTF) and resolving power (RP) in soft acrylic intraocular lenses (IOLs). SETTING: Faculty of Engineering, Chiba University, Chiba, Japan. METHODS: Folding procedures and other manipulations were performed on +18.0 diopter soft acrylic lenses (MA60BM, AcrySof, Alcon Surgical). The IOLs were then immersed in the water chamber of a model eye and MTF and RP under veiling glare light measured. The optical surfaces of the IOLs were examined microscopically. RESULTS: After the IOLs had been folded for 30 seconds, MTF recovered 8 and 6 minutes after unfolding in 20 degrees C 37 degrees C balanced salt solution, respectively. Prolonged folding of 10, 20, and 60 minutes did not affect the final MTF, which was measured 30 minutes after unfolding. However, RP deteriorated after the 60 minute folding. Optic damage was observed after the 20 and 60 minute foldings. Neither parameter changed after the IOLs were tightly folded for 30 seconds; however, both deteriorated slightly after the IOLs were tightly folded for 5 minutes, and minor damage was seen on the optics. With fewer than 10 artificial linear cracks in the central 3 mm of the optic, MTF was not affected; with 20 or fewer, RP was not affected. After forceps pressure on the central optic, MTF recovered within 6 minutes. CONCLUSION: The optical quality of soft acrylic IOLs are not easily affected unless extreme nonphysiological manipulations are applied.