No abstract

To characterize possible differences in endothelial cell changes after cataract surgery in patients with pseudoexfoliation syndrome (PSX).Methods: In this prospective, age-matched, controlled clinical study, 25 consecutive patients with PSX and 25 control patients with senile cataracts only were studied. All patients were treated with standardized cataract surgery. Sequential quantitative and qualitative morphometric endothelial cell analyses of the central and paracentral cornea were performed preoperatively and postoperatively at 1 day, 4 weeks, and 6 months using noncontact specular microscopy.Results: Preoperative endothelial cell counts were 9.9% (PϽ.05) lower in patients with PSX (2387±266 cells/ mm 2 ) than in controls (2648±349 cells/mm 2 ). The mean endothelial cell loss was 11.1% in the PSX group and 10.3% (PϽ.001 for both) in the control group, with no intergroup differences after 6 months. The mean endothelial cell area increased in both groups. Also, qualitative analysis revealed no significant differences in the endothelial repair mechanisms.Conclusions: Endothelial cell density is reduced preoperatively in patients with PSX compared with agematched controls. In patients with PSX, cataract surgery induced similar endothelial cell changes without increased endothelial cell loss postoperatively.

Thermal loading is a significant side effect during excimer laser surgery of the cornea. The maximal temperature rise, which is dependent on fluence and repetition rate of the radiation, amounts to 20 degrees C in excised corneas and 7.5 degrees C in the in situ cornea. The temperature decreases exponentially with increasing distance from the incision with a half-value distance of 610 +/- 100 micron. Exposure parameters are recommended to avoid temperature rises greater than 11 degrees C.

A theoretical model is presented that is able to explain for the first time the pressure drop across the trabecular meshwork. The ramified flow paths in the subendothelial region of the trabecular meshwork can be interpreted as a filter bed. Data from transmission electron microscope (TEM) photographs are the starting point of the theoretical consideration. Taking shrinkage of the sections into account, the pressure gradient across the subendothelial region amounts to 0.05 mm Hg. As these canaliculi are coated by a film of glycosaminoglycans (GAGs), the pressure drop is presumably a function of the film thickness. Only film thicknesses of 0.35 micron led to pressure gradients in the experimentally verified magnitude. As the whole filter bed probably does not contribute to the filtration but only about 10%, the pressure drop specified is reached when the GAG coating is 0.25 micron. As these values seem to be fairly realistic, it can be concluded that the subendothelial region of the juxtacanalicular meshwork (about 2 micron thickness) can be regarded as the "locus generis" of aqueous humor outflow resistance.

The diffractive bifocal IOL performed well at distance and near. Patients who no longer require spectacles will benefit significantly from a bifocal IOL, but many with a bifocal IOL in one eye will require spectacles for the fellow eye.