[Elasticity of capsulorhexis in the animal model]. / Die Dehnungskapazität der Kapsulorhexis im Tiermodell.

A special caliper was designed to determine the stretching capacity of a circular capsulorhexis allowing measurements in 0.02 mm increments. A small capsulorhexis 4.5-6.0 mm in diameter could be stretched 2.7 times; a large capsulorhexis 6.5-8.0 mm in diameter was stretched 2.6 times the original diameter. A smooth circular capsulorhexis is very strong and stabile but also has significant stretching capacity. In a small capsulorhexis, there is the danger that zonular fiber defects or posterior capsular rupture may occur during manual expression, of the nucleus. A large capsulorhexis is more suitable for manual nucleus delivery.

In vitro and in vivo evaluation of a hydrophilized silicone intraocular lens.

The surface of a silicone-disc intraocular lens (IOL) was hydrophilized by plasma etching (oxygen plasma) and compared to an untreated but otherwise identical IOL. Various methods of surface analysis were used to characterize the modification (e.g., X-ray photoelectron spectroscopy, contact angle estimation). A cytotoxic effect of the modified surface was excluded by cell culture experiments evaluating cell spreading, cell morphology, DNA and protein synthesis. In vivo experiments on rabbits indicated that the postoperative foreign-body reaction was not significantly affected by the hydrophilization of the IOL surface. Throughout the entire follow-up (12 weeks) we found less induced posterior synechias in the eyes with hydrophilized lenses than in those with untreated lenses (P = .009). While the IOL dislocations out of the capsular bag and the posterior capsular opacification rate did not differ significantly between the two groups of eyes, we did see special patterns of posterior capsular opacification on the posterior capsules of eyes with the hydrophilized IOL.

Variations in manufacturing quality of diffractive multifocal lenses.

The new generation of multifocal intraocular lenses (IOLs) based on diffraction optics is characterized by a stepped discontinuity at zone boundaries on the posterior surface of the IOL optic. The step height at the zone boundaries is less than 2 microns. There are approximately 30 zones on a 6 mm diameter lens, requiring manufacturing precision of about 0.02 mm. Various companies produce this type of lens. On two implanted lenses we found, in addition to the 2 microns boundaries, many small circular rims that appeared to be manufacturing artifacts. The presence of these artifacts may explain the variable clinical acceptance of these IOLs.

[Animal experiment studies of the biocompatibility of colored and plain lens haptics of polymethylmethacrylate]. / Tierexperimentelle Untersuchungen zur Biokompatibilität von gefärbten und ungefärbten Linsenhaptiken aus Polymethylmethacrylat.

In spite of the great clinical success of cataract surgery and intraocular lens implantation, adverse reactions still occur. In 2-3% of all cases, there is acute or chronic inflammation. One reason might be that the biocompatibility of the lens material is insufficient. This study evaluates the biocompatibility of dyed and undyed transparent PMMA lens haptics. The haptics were implanted subcutaneously in mobile and immobile mice tissue. After different implantation periods varying from 1 week to 6 months, the haptics were removed and evaluated histologically. The undyed PMMA lens haptics showed no adverse reactions. The dyed PMMA lens haptics showed a strong inflammatory response caused by diffusion of the dye into the surrounding tissue.

Sutured retropupillary posterior chamber intraocular lenses for exchange or secondary implantation. The 12th annual Binkhorst lecture, 1988.

The histopathologic findings of four eyes obtained postmortem with iris-sutured posterior chamber intraocular lenses (PC IOLs) are described. These IOLs were implanted as exchange procedures. In most instances, the loops were not situated in the ciliary sulcus but rather were suspended behind the iris and ciliary body. Therefore, the primary mechanism of fixation of iris-sutured PC IOLs appears to be the sutures themselves rather than adherence to the ciliary tissues. This report of four eyes is preliminary, but the pathologic analysis, showing few significant lesions attributable to the IOL, provides a reason for optimism for using this technique. A long-term clinical study comparing the results of sutured PC IOLs with those of anterior chamber IOLs (AC IOLs) used in secondary or exchange implantation, as well as collection and analysis of more pathologic specimens, should provide a more definitive answer as to the preferred procedure.

Protective effect of the anterior lens capsule during extracapsular cataract extraction. Part I. Experimental animal study.

In an experimental study using albino Rex rabbits, the intercapsular cataract extraction (ICCE) technique was performed in 20 eyes with a small anterior capsulotomy. A large, can opener capsulotomy was performed in another 20 eyes, and 10 unoperated eyes served as controls. Endothelial cell loss was determined by vital staining with Trypan blue and Alizarin red S stains. Average endothelial cell loss with the ICCE technique was 1.2%; with the can opener technique, the average cell loss was 6.6%. This difference was statistically significant (P less than 0.01). The percentage of endothelial cell loss in the control eyes was 0.5. A positive correlation between endothelial cell loss related to phacoemulsification time and/or the amount of irrigating fluid used existed for the can opener group only (P less than 0.01). These results demonstrate that the presence of an almost intact anterior lens capsule during removal of lens substance is protective to the corneal endothelium.

[Protective effect of the anterior lens capsule: corneal endothelial cell loss following intercapsular phacoemulsification compared with phacoemulsification with large open capsulotomy]. / Protektiver Effekt der vorderen Linsenkapsel: Corneaendothelzellverlust nach interkapsulärer Phakoemulsifikation verglichen mit Phakoemulsifikation mit grosser offener Kapsulotomie.

In an experimental study using rabbits, the intercapsular technique was performed in 20 eyes to make a small anterior capsulotomy. A large, "can opener" capsulotomy was performed in 20 eyes, and ten eyes (five non-operated animals) served as controls. Endothelial cell loss was determined by vital staining with Trypan blue and Alizarin red S. Average endothelial cell loss with the intercapsular technique was 1.2%; with the can opener technique the cell loss was 6.6%. This difference was statistically significant (p less than 0.01). The percentage in the control eyes was 0.05%. Positive relations between endothelial cell loss related to phacoemulsification time and/or the amount of irrigating fluid used existed for the can opener group only (p less than 0.01). These results demonstrate that the presence of an almost intact anterior lens capsule during removal of lens substance is protective to the corneal endothelium.