Long-term endothelial changes in phakic eyes with posterior chamber intraocular lenses
ABSTRACT To evaluate the long-term endothelial cell changes in phakic eyes after implantation of a posterior chamber phakic intraocular lens to correct high ametropia.
Department of Ophthalmology, University Hospital of Vienna, Vienna, Austria.
Thirty-four eyes of 21 patients having implantation of an implantable contact lens (ICL, Staar Surgical) for high myopia or hyperopia were prospectively examined. The minimum follow-up was 2 to 4 years. Preoperative and serial postoperative specular microscopy (Noncon Robo SP 8000, Konan) was performed to evaluate the long-term endothelial cell changes.
The mean preoperative endothelial cell density was 2854 cells/mm(2). The mean endothelial cell loss from preoperatively was 1.8% at 3 months, 4.2% at 6 months, 5.5% at 12 months, 7.9% at 2 years (n = 34), 12.9% at 3 years (n = 13), and 12.3% at 4 years (n = 11). All other endothelial cell characteristics remained stable during the 4-year follow-up.
Continuous endothelial cell loss was observed after ICL implantation during a 4-year follow-up. There was rapid cell loss until 1 year postoperatively, after which the rate of loss was no longer statistically significant. The percentage of hexagonal cells (polymorphism) and the coefficient of variation (polymegethism) remained stable during the 4-year follow-up.
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ABSTRACT: Detailed and exact preoperative examinations are required to secure postoperative results that are highly satisfactory for the patients. The most important measurements are refraction, corneal topography, biometry of the anterior and posterior chamber, as well as endothelial cell density. Each of the various pIOL types has special advantages, but may also entail risks. Anterior chamber pIOLs may influence endothelial cells and may cause pupil ovalization. Posterior pIOLs can provoke cataract formation and pigment dispersion. Since the implantation of a pIOL is elective surgery indications have to be fulfilled and possible contraindications have to be validated carefully. Finally, it has to be mentioned that only a few of the pIOLs described above have been tested in other studies and that only a few long-term examinations were available. Because of this, careful postoperative examinations of the mostly young patients have to be performed over a period of several years in order to minimize long-term complications.
Conference Paper: Sequential switching series resonant converter with phase shift control[Show abstract] [Hide abstract]
ABSTRACT: Properties of a two-section phase-shift-controlled sequential switching series-resonant converter with (and without) mutually coupled tank inductors are discussed. Results of computer simulation and prototype evaluation show that the low semiconductor switching stresses, typical of all resonant converters, are further reduced in this topology, and that highly reliable operation is indicated. Comparisons with conventional phase-shift-controlled topologies (i.e. without sequential switching) and with a PWM series-resonant converter are also presentedApplied Power Electronics Conference and Exposition, 1988. APEC '88. Conference Proceedings 1988., Third Annual IEEE; 03/1988